| Paper Number | Authors | Title | Keywords | Abstract |
| 1 | Jiin-Yuh Jang, Hsien-Shu Tsai | 3-D NUMERICAL SIMULATION OF IN-CYLINDER FLOW DURING THE INTAKE STROKE FOR A FOUR-STROKE ENGINE | numerical simulation,in-cylinder flow, intake stroke | The three dimensional, turbulent flow fields during the intake stroke for a four stroke real motored engine under both the quasi steady state and the moving valve-piston conditions are presented in this paper. The effects of turbulence are simulated by the turbulence model. For the quasi-steady state case, the predicted flow coefficients as a function of different valve lifts from 1-6 mm are agree very well with the experimental data. The swirl and tumble flow structures for the quasi- steady state case are significantly from those under the transient moving valve-piston condition. |
| 2 | J.W. Hoyt, R.H.J. Sellin | A MIRROR AND TRACER METHOD OF 3-D FLOW VISUALIZATION | tracer; 3-D visualization; turbulent-flow visualization; boundary-layer structures | A mirror suspended at 45° over the flow channel, together with glass channel side walls, is used to give simultaneous top and side views of a flow tracer, thus giving three-dimensional flow patterns. This very simple idea has been explored in a small water channel using a dye-streak tracer consisting of streamers of a shear-thickening and high extensional-viscosity mixture. The tracer has been developed for use under strongly eddying and turbulent flow conditions and is well adapted to visualising wake flows and large structures in the turbulent boundary layer. |
| 3 | V.V. Golub, T.V. Bazhenova, S.B. Shcherbak | DENSITY AND ENTROPY DISTRIBUTION DURING SUPERSONIC JET FORMATION | optical & numerical visualization, supersonic jet formation, starting vortex | The present paper describes the determination of thermodynamic and gas dynamic parameters during jet formation by means of optical measurement. A comparison is made with numerical calculation of key parameters. The impulsive jets were produced by a sonic nozzle installed at the end of the shock tube. The shock tube was connected to a vacuum chamber with optical windows. The jet formation pattern was recorded, as it evolved in time, by a Schlieren system and interferometer. The density distribution was obtained by the processing of the interferogramms. The flow parameter distributions (pressure, density, Mach number and entropy) of the impulsive nitrogen jet behind the axisymmetrical sonic nozzle were calculated and were compared with the schlieren pictures resulting in some new features of impulsive jets structure being identified. |
| 4 | Hu Hui, Toshio Kobayashi, Tetsuo Saga, Nobuyuki Taniguchi, Shigeki Segawa | INVESTIGATION ON THE TABBED JET MIXING FLOWS BY USING LIF AND PIV | jet mixing flow, mixing enhancement, PIV technique and LIF technique | An experimental investigation of the vortical and turbulent structure changes in the near field of a jet mixing flow caused by mechanical tabs placed at the exit of a circular nozzle had been conducted. The techniques of Laser Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV) were used to accomplish flow visualization, instantaneous quantitative concentration measurements and velocity field measurements of the jet mixing flow. Compared with a nature jet flow (a circular jet flow without mechanical tabs intrusion), the experimental results showed that, besides the existence of the well known streamwise vortices generated by mechanical tabs, the tabbed jet flow was found to have shorter potential core length, smaller size of the spanwise Kelvin-Helmholtz vortices, earlier appearance of small scale turbulent structures and bigger turbulent intensity. The bifurcation of the jet flow was also found in the tabbed jet flow due to the intrusion of the mechanical tabs. |
| 5 | Hiroshi Sakamoto, Kazunori Takai | A STUDY ON VORTEX FORMATION MECHANISM OF A OSCILLATING RECTANGULAR PRISM BY VISUALIZATION USING LASER SHEET IMAGING METHOD | oscillating rectangular prism, vorteoscillating rectangular prism, vortex formation mechanism, vortex shedding frequency, flow visualization, laser sheet imaging method | The rectangular prism having width to height ratio of B/H=3 is forced into rotary oscillation at angular displacement up to ± 7° and transverse oscillation at a maximum amplitude of 20% of the length of the front face in order to investigate on the mechanism of the vortex-induced oscillations of the rectangular prism with impinging leading-edge vortices. The behavior of impinging leading-edge vortices, trailing-edge secondary vortices and wake vortices are investigated on the flow visualized observation using a laser sheet imaging method. The relationship between these vortices and unsteady fluid forces is also determined to better understand the generation mechanism of the vortex-induced oscillations of the rectangular prism with impinging leading-edge vortices. |
| 6 | Shuichi Torii, Wen-Jei Yang, Shinzaburo Umeda | FLOW OVER A SLOT-PERFORATED FLAT SURFACE BETWEEN TWO PARALLEL PLATES | perforated plate, alternate crossing of flow, flow recirculation, numerical simulation, flow visualization | A theoretical and experimental study is performed to investigate unsteady, two-dimensional, incompressible fluid flow over both sides of a slot-perforated flat surface, which is placed in a two-dimensional channel. The governing boundary-layer equations are discretized by means of a finite-difference technique to determine streamwise and transverse velocity components. The roles of both the Reynolds number and the ratio of the slot width, d, to the plate thickness, t, on the velocity field are disclosed. It is found from the study that: (i) the flow pattern between two plates can be classified into four categories depending on a combination of Re and d/t, (ii) at a small value of Re and/or d/t flow over the slot exhibits no timewise variation, (iii) when Re and d/t exceed certain values, an alternate crossing of flow from one side of the plate to the other occurs across the slot, and (iv) a further increase in Re results in a complex flow both inside the slot and on the plate downstream of the slot. |
| 7 | T.A. Clarke, D. Mikielewicz, J. Stasiek | EMBEDDED AND TRUE-COLOUR IMAGE PROCESSING OF TLC FOR REAL-TIME 2-D AND 3-D HEAT TRANSFER AND FLOW VISUALIZATION | liquid crystal, DSP, 3-D temperature, 3-D flow | In recent years, high quality CCD sensors, frame-grabbers and image processing techniques have been applied to flow measurement with considerable success. Such measurement has allowed advanced techniques for visualization and analysis to be developed. In this paper Themochromic Liquid Crystal (TLC) particles are used to provide simultaneous spatial and temperature measurements for a liquid within a cavity. A novel image processing system is also described which allows simultaneous capture of particle locations and intensities from the RGB channels of a single CCD camera. This system is based upon a Digital Signal Processor (DSP) which is able to compute and store particle locations in real-time for up to a thousand targets. The eventual aim of the research is the real-time visualization of temperature, velocity vectors, and spatial distribution of particles. |
| 8 | Z. C. Liu and R. J. Adrian | VISUALIZATION OF HAIRPIN VORTEX STRUCTURE WITH PIV AND DNS | PIV, DNS, wall turbulence, vortices, hairpin vortices | visualizations of hairpin (horseshoe) vortices in channel flow have been performed with particle image velocimetry (PIV) and direct numerical simulation (DNS). The 2D PIV measurements of flows at different Reynolds numbers in a streamwise-normal plane and several streamwise-spanwise planes reveal hairpin vortex signatures that are elements of hairpin vortices in 3D space. A vortex identification technique based on the imaginary part of the complex conjugate eigenvalue of the velocity gradient tensor has been adopted for detection and visualization of vortices in a DNS velocity field in a 3D domain. The technique successfully locates hairpin vortices as well as quasi-streamwise vortices near the walls. The visualization demonstrates that hairpin vortices and quasi-streamwise vortices are the important and frequently occurring coherent vortical structures in wall turbulence and that they are associated with low-momentum and high-momentum streaks. These vortical structures contain regions of large Reynolds stress. |
| 9 | M. Novak, B. Širok, F. Trdiè | THE MEASUREMENT OF TIME FLUCTUATION OF BLUFF BODY VORTEX STREET WITH AID OF DIGITAL IMAGE-PROCESSING TECHNIQUE | bluff body, computer-aided visualization, power spectra, scalar patterns, vortex shedding, vortex street | In the paper the measurement of time fluctuations of vortex structures in a vortex street behind a bluff body using digital image-processing technique is described. Two-dimensional image of vortex street behind the prismatic bluff body in the wind tunnel was visualized with aid of a high-speed camera. The level of grey intensity in space and time forms scalar patterns which can be observed using computer-aided visualization. By successive digitalization of grey intensity distribution shots in restricted areas, simultaneous time series were generated. Power spectra describing a distribution of vortex structures in the bluff body wake was calculated. Results indicate that significant frequencies occur in the bluff body wake according to vortex shedding theory. The transition from recurrent behaviour, periodic or quasi-periodic, to non-periodic behaviour is represented by a change from a discrete to continuous spectrum. |
| 10 | J. C. F. Pereira and J. M. M. Sousa | NUMERICAL FLOW VISUALIZATION OF THREE-DIMENSIONAL VORTEX BREAKDOWN PRODUCED BY AN ENCLOSED ROTATING CONE | flow visualization, vortex breakdown, 3-D numerical simulation | The three-dimensional structure of confined vortex breakdown produced by a rotating cone is numerically investigated. Both steady and time-dependent regimes are considered. Numerical flow visualization is extensively used in the physical interpretation of the flow features |
| 11 | J. Gordon Leishman | TECHNIQUES FOR FLOW VISUALIZATION OF HELICOPTER ROTOR WAKES | vortices, wakes, helicopter rotors, flow visualization | This paper summarizes flow visualization techniques used to investigate helicopter rotor wakes and blade tip vortices. Unlike a fixed-wing aircraft, blade tip vortices remain close to the aerodynamic surfaces from which they were generated, as well as to each other and to the airframe surfaces. This results in set of complicated vortex/vortex and vortex/surface interaction phenomena. Techniques discussed include natural condensation, smoke/light-sheet, schlieren and shadowgraphy. Specific examples shown include tip vortex formation, blade-vortex interactions, wake instabilities, and vortex/airframe interactions. |
| 12 | K.C. Cheng and D.C. Owens | THE ROLE OF VISUALIZATION AND TEMPERATURE FLUCTUATION MEASUREMENT IN THE STUDY OF INSTABILITY AND TRANSITION PHENOMENA | rotating curved square channel, flow visualization temperature fluctuation measurement, instability and transition | The instability and transition phenomena for air flow in rotating curved square channels are studied by using smoke visualization and temperature fluctuation measurement techniques for Reynolds number Re = 2000 in the rotating speed range n = 0 ~ 350 rpm for positive and negative rotations. The measurement is based on the analogy between fluctuating temperature field and the fluctuating velocity component in the streamwise direction for forced convection using slightly heated air. The measurement results (instantaneous temperature signals, fluctuating temperature intensity) are interpreted in the light of secondary flow patterns revealed by flow visualization. The stabilizing and destabilizing phenomena caused by the simultaneous action of Coriolis and centrifugal forces are studied. The flow visualization reveals the Dean and Coriolis vortices caused by the respective instability problem. |
| 13 | Heinrich Stüer, Albert Gyr , Wolfgang Kinzelbach | 3-D PTV APPLIED TO LAMINAR SEPARATION ON A FORWARD FACING STEP | 3-D PTV, laminar separation, forward facing step | The separation on a forward facing step was investigated under laminar flow conditions using hydrogen bubble technique to visualise and PTV to evaluate the 3-D temporal velocity field in Eulerian representation in the vicinity of the step. Short-time averaged velocity fields allowed the construction of streamlines showing that the separation is topologically of an open bubble type with a span-wise quasi periodicity. The entrained fluid is continuously released by the front vortex, which breaks out of the separation bubble in longitudinal streaks. The topology of this dynamic behaviour is described and confirmed by streamlines. |
| 14 | P. Jeschke, R. Biertümpfel, H. Beer | VISUALIZATION OF LONGITUDINAL VORTICES AND SURFACE TEMPERATURES IN A NATURAL CONVECTION EXPERIMENT | thermochromic liquid crystals, longitudinal vortices, natural convection boundary layer flow, thymol blue-electrochemical flow visualization | The heat transfer of a natural convection flow field with longitudinal vortices was investigated. For this purpose, a constant heat flux flat plate was placed in water and the surface temperature distribution was measured using a wide band thermochromic liquid crystal (TLC). The boundary layer flow was visualized by an electrochemical method which took advantage of the colour change of the pH-indicator thymol blue. |
| 15 | Claude Béguier | ROTATING SPOON AS PARAMETRIC OSCILLATOR | hydrodynamical coupling, parametric oscillator, dynamical lure | The rotation spoon is a flying lure used to catch predatory fishes. It can be shown that its rotation is induced by the interaction between the mechanical pendulum composed of the spoon hooked to the fishing wire and the hy-drodynamic instability appearing in the near wake. This interaction confers to the rotating spoon the characteristics of a parametric os-cillator. Such a fluid-structure coupling is analysed from theoretical considerations and flow visualizations. |
| 16 | Antonello Cogotti | FLOW VISUALIZATION TECHNIQUES IN THE PININFARINA FULL-SCALE AUTOMOTIVE WIND TUNNEL | wind tunnel, automotive, full scale, flow visualization | Flow visualization techniques play an important role in the aerodynamic development of passenger cars and that is because they offer a real help in understanding the interaction between the flow-field and the car body. That is why some type of visualization technique has always been used in the automotive wind tunnels, since the beginning of aerodynamic testing on passenger cars. However, these techniques have undergone in the last 20 years an evolution, which has changed the way flow field visualization is carried out. And that is mainly true for the aerodynamic facilities of big size, like, for instance, the full scale wind tunnels where automotive companies develop the new passenger cars. The paper reports first of all, a short description of the visualization techniques used in the past in the automotive field. Then it reports a description of the techniques that are used today, mainly in the Pininfarina wind tunnel, to survey the flow-field around a full-scale car. |
| 17 | David F. Fisher, Edward A. Haering, Jr., Gregory K. Noffz, and Juan I. Aguilar | OBSERVATIONS OF SHOCK WAVES ON A TRANSPORT AIRCRAFT | flow visualization, flight test, gps, l-1011 aircraft, shock waves, shadowgraph | Wing compression shock shadowgraphs were observed on two flights during banked turns of an L-1011 aircraft at a Mach number of 0.85 and an altitude of 35,000 ft (10,700 m). Photos and video recording of the shadowgraphs were taken during the flights to document the shadowgraphs. Bright sunlight on the aircraft was required. The time of day, aircraft position, speed and attitudes were recorded to determine the sun azimuth and elevation relative to the wing quarter chordline when the shadowgraphs were visible. Sun elevation and azimuth angles were documented for which the wing compression shock shadowgraphs were visible. The shadowgraph was observed for high to low elevation angles relative to the wing, but for best results high sun angles relative to the wing are desired. |
| 18 | V.D. Goryachev | THE GRAPHICS PROCESSING OF CFD BENCH-MARKS DATA VIA INTERNET | computer fluid dynamics, visualization, benchmark, internet | The paper is devoted to motivation and description of software tools for access providing and online graphics processing of numerical simulation and experiment data - benchmarks from information system. The work has been developing as a database support part of Hypermedia Simulation and Information System (HSIS) where to build CFD applications able to be remotely accessible and independent from the architecture and hardware platform used. |
| 19 | H. Hinrichs, K.D. Hinsch, R. Netter, C. Surmann | LIGHT-IN-FLIGHT PARTICLE HOLOGRAPHY FOR VELOCIMETRY IN A WIND TUNNEL | 3d-piv, light-in-flight-holography | Much recent activity in experimental fluid dynamics requires instantaneous three-dimensional mapping of the flow field. Thus, classical velocimetry by particle imaging calls for extensions. It has been shown that holographic images of 3-D particle fields are a good source to extract corresponding velocity data. By light-in-flight holography the philosophy of sheetwise data extraction can be retained to achieve improved signal-to-noise ratio and good localization in depth. For this purpose the hologram is recorded with a light source of short coherence length (some cm) at oblique reference wave incidence. Slitwise reconstruction renders holographic images of thin shells in object space depth. While the basic performance of the technique has been demonstrated earlier, the present contribution shows the successful practical application in the study of a wind tunnel flow behind a cylindrical obstacle. The configuration is three-dimensional by viewing at an angle to the cylinder axis. |
| 20 | Hiroyuki Honji | PATTERN FORMATION IN AN ELECTROLYTICALLY-DRIVEN SQUARE VORTEX LATTICE | vortex lattice, two-dimensional flow, Lorentz force | Formation of quasi-two-dimensional vortex flow patterns in a nearly square vortex lattice has been investigated using a tracer-particle visualization technique. The vortex lattice has been driven electrolytically. It has been found that the vortex lattice remains regular when a dimensionless Lorentz force is less than 38 and the rotation of the lattice vortex system stabilizes the flow. |
| 21 | M. Keicher and A. M. K. P. Taylor | VISUALIZATION IN MODELS OF CONTINUOUS CASTING MOULDS | continuous casting process, mould, transient vortices, interfacial instabilities, entrainment | Quarter scale experiments in a water model of a mould with width L = 457 mm, simulating the continuous casting process of steel, were conducted. The flow pattern in the mould was examined for three different surface boundary conditions of increasing relevance to the real process in order to gain insight into the transient effects such as interfacial instabilities between the molten steel and a floating slag layer which might lead to entrainment of the floating layer and thus deterioration of the cast steel quality. Water, as a liquid steel simulant, was injected through a model of a submerged bifurcated entry nozzle into the mould at a jet Reynolds number of 17500. Laser sheet technique was employed to visualise the different flow patterns in the mould and a photographic record is provided which was obtained via a still camera and a CCD camera digital imaging system. Applying a solid top boundary condition restricted transient behaviour of the flow in the mould. |
| 22 | Susanne Lau, Marcin Kaniewski and Venkatesa I. Vasanta Ram | VISUALIZATION OF INTERACTION PATTERNS OF LONGITUDINAL VORTICES EMBEDDED IN A CHANNEL FLOW | longitudinal vortices, interaction patterns, channel flow | The present paper is a visualization study of the patterns of flow in a channel in which lon-gitudinal vortices are generated by winglets. The vortex patterns arising from three differ-ent but interrrelated geometrical configura-tions of winglets are the subject of the study. The Reynolds number range for flow visuali-sation extends from transition onwards, which is around 300 for this flow, up to 7000. The experiments have been conducted in a spe-cially built channel-flow facility which oper-ates with water as the flowing medium and in which the flow is visualised by seeded parti-cles. The video recording of the visualised flow shows the different stages of vortex for-mation and development. It brings out the similarities and differences between the pat-terns of formation and interaction of the vortices in the three winglet configurations. |
| 23 | Wojciech T. Konka | SIMPLE VISUALIZATION METHODS TO SUPPORT “CONVENTIONAL” INVESTIGATION OF NATURAL CONVECTION HEAT TRANSFER | natural convection, schlieren method, interferometer method | This paper describes observations and experiments in visualization of natural convection heat transfer, occurring predominantly around horizontal tube located in a vertical slot, heated from one side and cooled from the other. The Schlieren and the interferometer methods have been employed for observation of the convection phenomena. In order to improve clarity of experimental results, a personal computer (PC) was used in registration and graphical representation of the picture transformation process. The transformation method was based on a standard set of graphical computer programmes such as: Aldus Photo Styler, Corel Draw Graphics and alike. All the results obtained using these simple visualization methods compared successfully with “conventional” experimental study and numerical study, which were fully compatible with numerical results. |
| 24 | T. A. Kowalewski, A. Cybulski, M. Rebow | PARTICLE IMAGE VELOCIMETRY AND THERMOMETRY IN FREEZING WATER | natural convection, freezing, liquid crystals, particle image velocimetry and thermometry | A new experimental technique based on computational analysis of the colour and displacement of thermochromic liquid crystal tracers is applied to determine both the temperature and velocity fields of natural convection in freezing water. It combines Particle Image Thermometry and Particle Image Velocimetry. Full 2-D temperature and velocity fields are determined from two or more colour images taken for the selected cross-section of the flow. |
| 25 | Paul Krogmann, Erich Schülein | FLOW VISUALIZATIONS IN A SHORT-DURATION SUPER-/HYPERSONIC WIND TUNNEL | Schlieren or shadowgraphy, oil film interferometry, liquid crystal coatings | The paper describes the application of flow visualization procedures in the DLR Goettingen Ludwieg Tube Facility RWG. A brief introduction of the experimental facility and its main features will be presented. The techniques which are described in use in the facility are Schlieren or shadowgraph visualization of the flow fields, oil film interferometry to obtain skin friction data in complex flow field regions on a model and liquid crystal coatings which are used for visualization of the global thermal load distribution on a model. |
| 26 | N.P.Migoun, P.P.Prokhorenko | FLOW VISUALIZATION IN CONICAL CAPILLARY IMMERSED IN LIQUID | conical capillary, liquid film flow, liquid's meniscus | The phenomenon of the filling with liquids of one-side closed capillaries was established ten years ago, but its physical nature is not entirely clear up to now. New experimental and theoretical results are presented and compared. It is shown satisfactory correspondence between theoretical and experimental results. |
| 27 | M.W. Prazak and T.J. Mueller | HYDROGEN BUBBLE VISUALIZATION OF THE FLOW OVER A THIN WING AT CHORD REYNOLDS NUMBERS FROM 12,000 TO 21,000 | aerodynamics, drag, Eppler 61, hydrogen bubble technique, lift, very low Reynolds numbers | The results of an experimental study on a finite wing with an Eppler 61 profile at very low chord Reynolds numbers are presented. Data for separation location were obtained for chord Reynolds numbers ranging from about 12,000 to 21,000. Force balance and hydrogen bubble flow visualization equipment were employed in the water tunnel facility in the main laboratory at the Hessert Center for Aerospace Research at the University of Notre Dame. |
| 28 | Marcus Schäfer, Peter Wächter, Franz Durst and Murad Ismailov | TURBULENT FLOW IN HYPERBOLOID STIRRING REACTOR | mixing, stirred tank reactor, hyperboloid stirrer, laser-Doppler velocimetry | The present paper provides detailed information on the flow field produced by a hyperboloid stirrer equipped with eight transport ribs in a fully-baffled vessel of diameter T = 152 mm and describes a technique to visualise its flow characteristics using laser-Doppler velocimetry (LDV). The diameter of the hyperboloid stirrer was D = T/3 and the liquid height was equal to the tank diameter. All measurements were conducted at a constant rotational speed of N = 2,060 r.p.m (Re = ND/n = 5,610). Beside investigations on the bulk flow generated by the hyperboloid stirrer particular attention was drawn to the formation of trailing vortices discharged from the impeller. The bulk flow field obtained by the LDV-measurements reveals the typical mode of operation of a hyperboloid stirrer. Fluid is entrained to the impeller region from above and is then discharged in form of a 45° downward inclined jet. A large scale vortex is formed that spans over approximately half of the liquid height. |
| 29 | Ryu-ichiro Ohyama, Kiyoji Kaneko | VISUALIZATION OF ELECTROHYDRODYNAMIC FLUID MOTION COUPLED TO CURRENT FLOW ALONG DIELECTRIC LIQUID SURFACE | ehd flow, dielectric liquid, current flow, fluorescence, hydrodynamic drag | In this paper a flow visualization technique using the streak line method for electrohydrodynamic (EHD) fluid motion of dielectric liquids is presented, and optical characterization of the EHD flow with a vortex created under AC electric fields is shown. The EHD flow is an interesting phenomenon because the fluid motion by AC electric fields is a rare case. In the EHD flow visualization by tracer methods, it is required that dielectric properties of the tracer maintain an adjustment with those of the EHD liquid. This requirement has been satisfied by development of a fluorescent dielectric liquid made of the EHD liquid and an infinitesimal fluorescencer. The EHD flow visualization is realized by exciting streak lines of the fluorescent dielectric liquid. The driving action causing the EHD fluid motion is the drift of charges which are emitted from an AC high voltage electrode in air. Since the charges run on the surface more ease than in the liquid, the surface molecules are dragged by the charge running. |
| 30 | Gary S. Settles, Aaron D. Brandt, and James D. Miller | FULL-SCALE SCHLIEREN IMAGING OF SHOCK WAVES FOR AVIATION SECURITY RESEARCH | Schlieren imaging, shock waves, explosives, aircraft, terrorism, high speed photography | A multi-flash light source and a large-scale, lens-and-grid-type Schlieren system have been used to image shock wave motion generated by small explosions in scenarios representative of terrorist bombings of com-mercial jetliners. It was demonstrated that even very weak explosions, producing shock waves only marginally faster than the acoustic speed, could be made visible. Stronger shocks due to a few grams of explosive mixture were found to travel at Mach numbers up to 1.2, and thus to have overpressures up to about ½ atmosphere. The utility of such explosions to study shock motion in an aircraft cabin has been demonstrated qualitatively by imaging the shock waves due to explosions underneath full-sized aircraft seats. This approach may be of value in aircraft hardening studies. |
| 31 | B W Skews | COLOUR ENCODED VISUALIZATION APPLIED TO THE HYDRAULIC ANALOGY FOR SUPERSONIC FLOW | water table, ripple tank, colour coding, water surface slope, hydraulic analogy | A system for producing images of water surface waves where the local slope of the surface is colour coded is described. The technique is applied to the study of wave phenomena around wedges, using a water table (ripple tank) with particular application to the shallow water analogy for supersonic flow. A very simple implementation of the system using a Fresnel lens from an overhead projector is shown to give good results. Image processing allows the capillary waves to be separated from the main bow wave phenomena. A second implementation with significantly higher sensitivity using a parabolic mirror is also demonstrated. |
| 32 | Yongda Sun, Yongfang Sun | NOVEL METHOD OF HEMODYNAMIC PERFORMANCE TESTING OF MECHANICAL HEART VALVES | dynamic flow birefringence, mechanical heart valve, shear stress | In this paper, the fundamental theory and experimental method of dynamic flow birefringence (DFB) have been studied extensively under the consideration of an application to hemodynamic performance testing of mechanical heart valves. The method utilises the optical interference patterns observed in the birefringent flow for determination of the fluid shear-stress and velocity distribution. |
| 33 | H.Takenaga, T.Matsuda and H.Yokota | AN EXPERIMENTAL STUDY ON LABYRINTH SEALS FOR STEAM TURBINES | discharge coefficient, oil flow, visualization | In order to improve performance of the labyrinth seals used for the steam turbine gland packing, an experimental study was carried out, using two dimensional labyrinth seal models. The effect of the labyrinth seal geometrical parameters (the seal clearance, the seal pitch and the short fin number) on seal performance was obtained and the internal flow pattern of the tested labyrinth seal models was obtained by oil flow visualization. Effective ways to improve seal performance, based on the experimental test results, is shown. |
| 34 | Shohei Takatani and Junjiro Iwamoto | EXPERIMENTAL STUDY ON THE OSCILLATION OF UNDEREXPANDED IMPINGING JET | oscillation, shock wave, feed back, underexpanded jet, sound wave | This work is concerned with an experimental study of flow due to underexpanded axisymmetric jet impinging on a flat plate placed perpendicular to the jet axis. The pressure history is measured at the center of the plate and the Schlieren photographs are taken to observe the change in flow pattern of the impinging jet. As a result in the experiment, the oscillation pattern of underexpanded impinging jet is found. Then, the mechanism of oscillatory phenomenon of the impinging jet is examined and discussed in the present paper. |
| 35 | B W Skews E V Timofeev P A Voinovich K Takayama | HIGH RESOLUTION EXPERIMENTAL AND NUMERICAL VISUALIZATION OF THE UNSTEADY REFLECTION OF CURVED SHOCK WAVES | shock wave reflection, holographic interferometry, numerical interferometry | This paper is an attempt to explore to what degree the transition between the types of reflection of unsteady curved shock waves can be described by the theory derived for steady plane waves. The reflection has to be remote from a wall in order to avoid thermal and viscous boundary layers. In the present case two identical curved waves are allowed to reflect off each other on a plane of symmetry. The type of reflection is established experimentally using holographic interferometry. Reconstructed interferograms and shadowgraph images derived from the holographic plate are used to establish the flow conditions. It is found that with even the highest resolution available using these techniques, the issue could not be resolved. Numerical predictions at much higher resolution are resorted to. Contour plots and numerical interferograms are produced in order to establish the reflection type. This latter technique has the marked advantage of being able to generate an arbitrarily fine fringe spacing . |
| 36 | Josef Tanny, Bachtiyar Yakubov | SCHLIEREN FLOW VISUALIZATION OF INSTABILITY PHENOMENA AT A DOUBLE DIFFUSIVE INTERFACE | double diffusion; instability; Schlieren technique; flow visualization; density interface | Flow patterns and instability phenomena at a density interface in a two-layer stratified system in a laterally heated enclosure were studied using the schlieren flow-visualization technique. Due to the lateral heating of the enclosure, a circulating flow is induced in each layer such that the interface separating the layers is simultaneously exposed to destabilising shear and double diffusive convection. The main goal of this work is to visualise the instabilities at the interface and to investigate their role in the mixing process of the two-layer system. The experiments were carried out in a box with inner dimensions of 10 x 10 x 10 cm. Two sidewalls of the box were made of stainless steel and served as heat exchangers, and the two other sidewalls were made of optical glass. The schlieren system consisted of two spherical mirrors, 15.24 cm in diameter and 152.4 cm in focal length. The output of the schlieren system was imaged by a CCD camera. |
| 37 | Jean Tensi, François Paillé | VISUALIZATION OF THE FLOW AROUND A CYLINDER, USING STEADY AND UNSTEADY BLOWING TECHNIQUES | active flow control, blowing, cylinder, fluidic actuators, oscillating wake, smoke visualization, synthetic jets | The oscillating wake behind a 2-D cylinder is investigated, using steady and unsteady blowing techniques, as part of a program of research into drag reduction and bluff body control. The experiments were conducted in a low-speed tunnel (Reynolds number : 360). visualizations of the flow in a plane normal to the cylinder were realized. Comparisons are given on the effects of steady blowing jets and synthetic jets on the wake : formation of closed recirculating regimes and reduction of the oscillations. |
| 38 | Wang Xiao, Toyohiko Suzuki, Yoshitaka Ochiai, Tetsuya Oda | NUMERICAL FLOW VISUALIZATION OF TURBULENT DIFFUSION FLAME OVER A VERTICAL FLAT WALL | numerical simulation, flow visualization, turbulent diffusion flame, boundary layer flow | Numerical flow visualization is carried out for a turbulent diffusion flame over a combustible vertical flat wall. At the wall surface, thermal pyrolysis occurs and gasified fuel is injected into a boundary layer over the wall when heated. A theoretical model for the numerical flow visualization is presented coupling aerodynamics with chemistry. One-step overall irreversible chemical reaction is adopted with fast chemistry and models including radiation loss and buoyancy are also incorporated. Effects of main stream velocity, radiation loss and buoyancy on injecting velocity, turbulence and diffusion flame are investigated. |
| 39 | Qing-ding Wei, Xiang-dong Du, Guang Chen, Jun Chen | VISUALIZATION STUDY ON THE VARIATION OF STRUCTURE OF THE JUNCTURE FLOW OF A SHORT SQUARE CYLINDER MOUNTED ON A FLAT PLATE IN A LARGE RANGE OF REYNOLDS NUMBER | juncture flow, visualization, laser induced fluorescence, horseshoe vortex | The structures of juncture flow of a short square cylinder mounted on a flat plate were experimentally studied through the method of laser induced fluorescence. The experiment was conducted in a water tunnel with low turbulence intensity which is less than 0.3%. The test Reynolds number was changed from 2,000 to 20,000, and three typical flow patterns were visualized clearly which correspond to three different Reynolds number ranges respectively. The pattern I shows regular horseshoe vortex shedding from smooth separated shear layer. The pattern II shows irregular horseshoe vortex shedding from irregular separated shear layer. The pattern III shows intermittent or continual turbulent flow. The phenomena of vortices merging and wrapping can be observed clearly. |
| 40 | R.H.S Winterton, O.C. Jadayel, J.S. Munaweera | VISUALIZATION OF LIQUID-GAS BUBBLY FLOW | bubble, size, visualization, software, bubbly flow. | In two fluid models of vapour-liquid two phase flow the calculation of the exchange of heat, mass or momentum between the phases requires a knowledge of the area of the interface. In bubbly flow this is linked to the bubble size. In spite of the importance of this information the experimental studies in the literature seem to be limited in scope. In many cases electrical probes have been used to measure bubble size but some of the information available from photography is lost. The purpose of the experimental programme recently started at Birmingham is to overcome some of these limitations. Bubble diameter has been measured in a range of duct sizes for a range of gas and liquid mass fluxes, with air/water. To the extent that it is possible to talk about fully developed two phase flow, it is the intention to reach this condition, with entry lengths up to 100 times the duct diameter. A video technique is used to record the shape of the bubbles and thus find the average diameter. |
| 41 | Gennaro Zuppardi, Rodolfo Monti, Giuseppe P. Russo | THERMOGRAPHIC ANALYSIS OF THE LEE-SIDE VORTI-CAL STRUCTURES ON DELTA WINGS IN SUPERSONIC FLOW | thermography, delta wings | The unsteady computerized thermographic technique is used to evaluate the surface patterns of the Stanton number that are the imprints of the flow field. On delta wings the relative minima and maxima of the Stanton number identify the beginning and the end of a laminar/turbulent transition region, the separation and reattachment lines and hence a picture of the lee-side vortical structures. Tests have been performed at M = 1.92 on two models of delta wings with subsonic edges having two different sweep angles. |
| 42 | Gregory A. Addington, Robert C. Nelson | A NON-INTRUSIVE FLOW VISUALIZATION TECHNIQUE FOR USE IN WATER TUNNELS | water tunnel flow visualization, shear layer visualization | A means of visualizing boundary layer and separating shear layer flows unobtrusively in water tunnels has been extended and tested. This technique involves a highly-soluble dye film covered by a less-soluble protective coating. The resulting flow visualizations act as a bridge between surface flow visualization and smoke flow visualization results. Application of this technique to the visualization of secondary and reverse flows over a 65° delta wing are used to demonstrate this method’s utility. |
| 43 | Tore Loeland, Lars R. Saetran, Reidar Sakariassen | EXPERIMENTAL INVESTIGATION USING PIV AND LASER SHEET VISUALIZATION IN CAVITY FLOWS | piv, visualization, cavity, experimental | In the cavity flow problem there is a possibility of obtaining a steady vortex. In the present work Laser Sheet visualization and Particle Image Velocimetry, PIV, have been used to characterize the vortex structure inside three different cavities. The results show that by using Cross correlation instead of Auto correlation, the PIV technique do not suffer from directional ambiguity, and can be used in vortical flows like the cavity flow problem. |
| 44 | Peter Bernsteen, Ulf Johansson, Sören Knuts, Lars Ljungkrona | WATER FLOW TEST WITH A MODEL OF A MANIFOLD AND INJECTOR SYSTEM FOR SUPERSONIC FILM COOLING | visualization, water, supersonic film cooling | This paper presents results from visualization and pressure measurements on the flow in a feeding system, for injection of a supersonic cooling film. Starting with a simple model for water flow visualization in order to try out the best inlet design. Then going on to water and air testing with an exactly scaled model , for verification of the chosen design. The results show great improvement of the manifold flow characteristics between the different tests as well as successful development of a model manufacturing method for transparent flow test models with complex geometry. |
| 45 | K.Aoki , H.Okanaga , T.Munakata and Y.Nakayama | THE FLOW CHARACTERISTICS AND THE FLOW VISUALIZATION OF LOW WIND PRESSURE CABLE | circular with groove, pressure distribution, and drag and lift coefficient, spark tracing method | Many studies on the reduction of drag have been done, but it has not yet been made clear about what parameter of roughness the cause depends on when there are groove on the surfaces of circular cylinders. Therefore this study is used circular cylinders with various kind of shape of grooves for cable model and it investigated what characteristic pressure distribution, drag and lift coefficient, velocity distribution of the circular cylinder with groove for subcritical and critical Reynolds number ranges, respectively. From these results, pressure distribution, drag and lift coefficient, velocity distributions are made clear the characteristic changes for subcritical and critical Reynolds number ranges, respectively. |
| 46 | Yuichi Nkamura | VISUALIZATION OF DYNAMIC BEHAVIOUR OF STRESS WAVES AND CRACKS IN CONTROLLED BLASTING | shadowgraphy, high-speed videography, stress waves, cracks, controlled blasting | Model experiments were carried out by means of high-speed photography to understand the dynamic behavior of stress waves and cracks in blasting processes for the development of fracture control methods. A shadowgraph system using a Q switched ruby laser was set up for visualization of stress waves. A high-speed video camera system of the digital storage type was used to record the dynamic fracture process. In this paper, three methods for achieving the high degree of fracture control were presented. The shadowgraphs showed the stress wave interactions in the blasting process. High-speed video images clarified the dynamic behavior of cracks propagating along the control fracture plane. These results show that the presented methods are effective in controlling the orientation of the fracture plane and in driving the controlled cracks to greater distances. |
| 47 | Georges M. Quénot, Jaroslaw Pakleza, Tomasz A. Kowalewski | PARTICLE IMAGE VELOCIMETRY USING OPTICAL FLOW FOR IMAGE ANALYSIS | particle image velocimetry, optical flow | The aim of our investigation was to explore a new method of analysing flow images, based on the optical flow technique. Conventionally, this technique was developed for detecting motion of large objects in a real world scene. Applied to the flow images, it appears to be an interesting alternative offering high evaluation accuracy without most of the typical limitations characteristic of FFT based PIV. Besides evaluation of tracer images, the new method was also tested with smoke images obtained from experiments both in a fluidised bed and in a wind tunnel. It was also successfully tested on an image sequence of a vapor bubble growing on a thin heated wire. The accuracy of the velocity measurements using the new implementation was investigated using synthetic particle image sequences generated with the help of a 2D numerical simulation. |
| 48 | Youren Xu, Hongwu Tang, Yi Shi | USING LOW POWER LASER IN DIGITAL PARTICLE IMAGE VELOCIMETRY | digital image velocimetry, low power laser, image intensifier | In this paper an experimental system is presented to show the possibility of using low power laser (10 mw He-Ne laser) as light source in the DPIV technique. A CCD camera with image intensifier was used in the experimental system instead of an ordinary CCD camera to capture PIV images. In order to extend the limits of velocity measurement the laser light illumination was chopped to form a series of pulses. A simple electronics was designed to synchronize the light pulses with the CCD camera. |
| 49 | Ay Su, Ying-Chieh Liu | PULSATING PROCESS OF JET-IMPINGING FLAME | pulsation flame, jet-impingement | Experimental investigations on the pulsation jet-impinging diffusion flame were executed. A solenoid valve was aligned upstream of the jet orifice of methane fuel and controlled in open-closed cycles from 1 Hz to 25 Hz. Three impinging angles, 90 deg, 75 deg and 45deg and Reynolds numbers, Re = 148, 241 and 334, were conducted. Results shown that the open-closed cycles increase the flow intensities obviously. The pulsation flame profiles are corresponding to the actions of solenoid valve. As compared with the continuous flame, the pulsation flame has lower heat transfer rate to the flat plate. Results show that the minimum pulsating frequency for sustaining the pulsation is 3 Hz. |
| 50 | Ernst Winklhofer, Harald Philipp, Alois Hirsch | DIESEL SPRAY TRACKING AND SPRAY VELOCITY MEASUREMENTS WITH A HIGH SPEED LINE CAMERA | diesel engines, sprays, spray atomisation, velocities | A linear arrangement of optical fibers together with fast, parallel data acquisition techniques is used for the recording of length-time and diameter-time variations of diesel sprays in the optically accessed combustion chamber of a spray research engine. The high speed line camera enables the visualization of temporal propagation events. Spray length-versus-time traces are evaluated to yield spray velocities. Results are compared with fuel injection system and with engine parameters. Spray diameter-versus- time data demonstrate the effect of mechanisms involved in the breakup of diesel sprays. Time intervals and frequencies characteristic for the disruption and the breakup of the turbulent spray are found to represent the influence of cavitation and of flow instabilities. |
| 51 | Alexander L. Yarin, Daniel A. Weiss | DROP IMPACT ONTO WET SOLID SURFACES: KINEMATIC DISCONTINUITIES | drop impact, kinematic discontinuity | We investigate experimentally and theoretically the impact of liquid drops onto solid surfaces covered by a film of the same liquid. First, we consider experimentally the impact of monodisperse drops impinging one by one with the same velocity onto an initially dry wall. The impact process is observed using a shadowgraph technique and a CCD-camera. Illumination is synchronized with the drop generator. We find that the drops spread along the solid wall after impact. If the impact speed is sufficiently high (i.e. the non-dimensional impact speed U is larger than about 18), a liquid sheet arises roughly normally to the film. This sheet (a corona) moves outwards from the axis of impact, and small droplets are formed at the rim on its top. Then we also simulate the impact of single drops onto a quiescent liquid film. We take into account surface tension and gravity, and we show that viscous and compressibility effects can be neglected. |
| 52 | Uwe Brummund, Bérangère Mesnier | FLOW FIELD VISUALIZATION OF NON-REACTING AND REACTING SUPERSONIC FLOWS IN A SCRAMJET MODEL COMBUSTOR USING NON-INTRUSIVE OPTICAL DIAGNOSTICS | visualization, supersonic flows, optical diagnostics | The research on Supersonic Ramjet (SCRAMJET) combustors motivated the work on new non-intrusive measurement techniques to study the flowfield inside of a combustor during operation. This was possible by the development of new powerful laser systems and cameras with high spatial and time resolution. In this paper we report an investigation of a Mach 2 supersonic ramjet combustor in order to characterize flow properties in a supersonic reacting and non-reacting flow-field. Hydrogen was injected parallel to the center line of the combustion chamber through holes at the base of a symmetric wedge into a vitiated air stream. The wedge was centered as a strut in the two-dimensional model chamber. For investigating the reacting case we were especially interested in visualization of the turbulent supersonic flame structure. |
| 53 | PV Grigor'ev, YuP Makarov and GA Pozdniakov | THE SECOND KIND INSTABILITY OF SHOCK HEATED KRYPTON PLASMA IN EXPERIMENT ON SHOCK TUBE | instability, ionization, shock wave, relaxation zone, self-oscillation, shock-heated plasma | Periodical variations have been observed in ionisation relaxation time within the period of 55 micro sec at a constant velocity of a shock wave in krypton. Additionally, it has been determined that within any one cycle of the ground self-oscillation, the maximum attainable level of plasma radiation intensity is subject to periodical variation, and so too is the structure of the relaxation zone. |
| 54 | Xiaodong Tian, Yuliang Li, Yunsheng Li, Jiafan Chen, Changzhao Yu | INVESTIGATION OF TRANSPORT IN THE WAKE OF AN ISLAND OR A PENINSULA BY DPIV TECHNIQUE | dpiv, flow visualization, wake, vortex. | This paper describes an experimental investigation of transport process in the near wake of an island or a peninsula at a Reynolds number from 1050 to 5490. The experiment was done in a flume with the length of 26 meters and the width of 0.6 meters. The flow in the first four diameters of the wake was measured using DPIV(Digital Particle Image Velocimetry) technique. DPIV is a kind of technique which is developed in recent years. Its main advantage is available simultaneously and quickly for two components of the velocity. Enormous experimental measurements for smooth bluff bodies have been done in past dozens of years, particularly for circular cylinders. But because of restriction of single-point measurement method, obtaining a clear and reliable whole quantitative flow field simultaneously is difficult. The present work reports on a DPIV study, in which the mean and the random components of the flow velocity past different bodies at different Reynolds number were obtained. |
| 55 | H. H. Lee, J. Y. Hwang, S. H. Chung, and W. Lee | VISUALIZATION AND CONTROL OF BUOYANT DIFFUSION FLAMES WITH PERIODIC FUEL SUPPLY | diffusion flame, buoyancy-driven instability, flame oscillation, flame control, buoyancy-driven vortex, excitation-driven vortex | Characteristics of co-flow diffusion flame oscillation are visualized using a reactive Mie scattering (RMS) technique and their frequencies are measured using a photodiode. Results show that flame oscillation occurs in three different regimes by the interaction of buoyancy-driven natural oscillation and periodic fuel supply. With low frequency excitation, flame oscillation occurs with the frequency of multiple values of excitation frequency. Flame oscillation frequency becomes that of excitation frequency in the intermediate excitation frequency regime. With high frequency excitation, flame oscillation frequency becomes independent of excitation frequency, which corresponds to the natural oscillation frequency. |
| 56 | S. Matlok P. S. Larsen E. Gjernes J. F. Hansen | MIXING STUDIES IN A 1:60 SCALE MODEL OF A CORNERFIRED BOILER WITH OFA | laser sheet visualization, concentration distributions, spatial structures, LDA-data | In a model of a boiler, concentration distributions of injected gas into a swirling bulk flow are determined from quantitative laser-sheet visualization. Together with LDA-measurements of velocity fields this describes the mixing process and its efficiency expressed by several measures (unmixedness, spatial scales and correlations) as function of distance downstream of point of injection. Experimental results are compared to those of numerical calculations. The visualization scheme is analysed for experimental uncertainties in terms of calibration procedure, seeding type and concentration, scale resolution and noise. The scheme allows rapid assessment of effectiveness of mixing for various nozzle configurations. |
| 57 | Christophe Journeau , Yves Jung, Jocelyn Pierre | VISUALIZATION OF A 2000°C MELT SPREADING OVER A PLANE | flow spreading, high temperature, flow shape, flow front, geometrical calibrationfront, geometrical calibration | The spreading of high-temperature molten oxides are visualised by video and infrared cameras. To obtain data on the flow front progression, the camera images must be calibrated. Calibration of a high distortion wide angle camera and the use of ‘checkerboard’ calibration decks are shown. The flow shape has been determined and the progression velocity is estimated between 5 and 20 cm/s depending on the experimental conditions. The rhythm of the front progression seems to be due to the presence of a viscous skin. |
| 58 | F.M. Sinclair, P. Birkby, A.M. Savill, R.S. Cant and W.N. Dawes | NUMERICAL FLOW VISUALIZATION USING RESULTS FROM AN UNSTRUCTURED ADAPTIVE MESH | CFD, numerical, graphical display, adaptive mesh, virtual reality, mesh decimation | Methods of visualization of the results from CFD analyses performed using an unstructured adaptive mesh are presented. Methods of reducing file size and memory requirements and increasing animation speed are considered. Virtual Reality is used to enable the results of three-dimensional cases to be presented, showing two variables simultaneously. |
| 59 | Tatsuo Nishimura, Sosyun Sakura, Takao Sejima and Kuniaki Gotoh | THE STRUCTURE OF THE DIFFUSIVE INTERFACE IN A SALT-STRATIFIED TWO-LAYER SYSTEM UNDER A HORIZONTAL TEMPERATURE GRADIENT | double-diffusive convection, laser induced fluorescence technique, three-dimensional structure, self-sustained oscillation | A two-layer, salt-stratified NaCl-H20 system destabilized and mixed by lateral heating and cooling is considered. Flow visualizations are performed to examine the structure of the diffusive interface separating convection layers. The laser induced fluorescence technique reveals that a regular three-dimensional flow structure appears within the interface, which has not been known previously. Furthermore, self-sustained oscillation occurs within the interface due to the interaction of heat and mass transfer. The period of oscillation is found to be inversely proportional to the 0.5 exponent of the imposed horizontal temperature difference. |
| 60 | Michitoshi Takagi, Yujii Shihara | VISUALIZATION OF UNSTEADY WAKE STRUCTURES USING ESP SENSORS | visualization, unsteady wake, circular cylinder, sphere, pitot pressure, ESP sensor | The wake survey or Pitot traverse in the wake of a model is useful to understand the wake structure and the origin of the aerodynamic force acting on the model. Usually total pressure and/or velocity vector distributions are measured in these experiments. In this type of experiments, the measured pressures and velocities are regarded as ‘steady’ but of course the flow is 'unsteady' to some extent. Recently the authors have developed a system for measuring the unsteady pressures up to spatial 256 points and frequency of 300 Hz. The system consists of a commercially available instrument to measure steady pressures based on ESP (Electronically Scanned Pressure) sensors, 16 A/D converters and a personal computer to control the whole system and acquire data. A FFT (Fast Fourier Transform) based convolution integral enabled to compensate the frequency response function of the tubes connecting the pressure taps and the ESP sensors. |
| 61 | Claudia Cenedese, Stuart Dalziel | CONCENTRATION AND DEPTH FIELD DETERMINED BY THE LIGHT TRANSMITTED THROUGH A DYED SOLUTION | concentration, transmitted light, dye, baroclinic vortices. | In this paper we analyse a method to determine the dye concentration and the depth of a dyed solution by measuring the reduction in the intensity of light transmitted through the dyed solution, as compared to that transmitted through a clear solution. In other contexts the basis of this technique is often referred to as “optical thickness” and gives a measure of the average concentration of the dye over the whole fluid thickness h. However, for layered fluid flows, we may instead measure the depth of a layer by marking one layer with a uniform concentration of dye so that the attenuation due to the dye is confined to that layer and thus measurements of the optical thickness give the depth of the dyed layer. In this paper we present a detailed description of procedures required to derive the dye concentration (averaged along light rays) from an intensity field, and, ultimately, the thickness of the dyed layer. |
| 62 | Stuart B Dalziel, Graham O Hughes, Bruce R Sutherland | SYNTHETIC SCHLIEREN | Schlieren, internal waves, image processing | This paper outlines novel techniques for producing qualitative visualizations of density fluctuations and for obtaining quantitative whole-field density measurements in two-dimensional stratified flows. These techniques, which utilise image processing technology, are much simpler to set up than the classical schlieren and interferometry methods, and provide useful information in situations where shadowgraph is of little or no value. Moreover, they may be set-up to analyse much larger domains than is feasible with the classical approaches. Application of these techniques is illustrated by an internal wave field produced by an oscillating cylinder. |
| 63 | W.R. Dunn, S. Tavoularis, B.H.K. Lee | VISUALIZATION OF FLOW PAST A MODEL OF A FIGHTER AIRCRAFT IN A WATER TUNNEL | water tunnel, F/A-18, leading edge extension vortex | Incompressible flow past a 1:48 scale model of the F/A-18 fighter aircraft was studied in a water tunnel at a Reynolds number of 3450, based on the free stream velocity and the wing’s mean aerodynamic chord. Flow around the aircraft’s stores was studied at low angles of attack. Dye streaklines clearly show that the flow between closely-spaced stores is considerably slower than flow around the clean wing. Vortices emanating from the F/A-18’s upper surface were studied in the high angle of attack range. A non-Newtonian, shear-thickening dye followed the Leading Edge Extension (LEX) vortex core downstream to the vortex breakdown location, which remained visible despite highly chaotic motions. The vortex bursting locations agree with results from other model and full-scale studies. |
| 64 | Gong Xin Shen, Li Duan | HPIV APPLIED TO 3D-FLOW | holograph, piv, spiv, cross-correlation | It is still one of the main problems to observe and measure the non-steady and spatial complex flows for the fluid mechanics. Except 2D-PIVand SPIV, the Holographic Particle Image Velocimetry ( HPIV ) is one of the approaches to measure instantaneously the three component ( u, v, w ) velocity vector field in a full 3D volume ( space ). In this paper, the displacements of the particles in a volume of the flow was recorded instantaneously by a holographic recording system which was designed specially. Using the two exposure pulses of YAG lasers separately, the diffused illuminating lights and the reference lights with a symmetric optical arrangement, it could have the reconstruction of the holographic fields of the particles with different exposures time and use the cross-correlation method to determinate the directions of the displacements of the particles. Using the stereoscopic PIV ( SPIV ) technique here, the particle images of every sectional view with a certain thickness in the holographic volume could be captured with stereoscopic method. Finally the instantaneous 3-component velocity vector field in a 3-dimensional volume of the flow was provided. The HPIV technique here was applied to a diagonal flow passed a cubic box ( 100 100 100 mm ) and some results were given. |
| 65 | Jongmin Shin, Wen-Jei Yang, Chung-Sheng Wu | NUMERICAL VISUALIZATION OF FLOW INSIDE INTERSECTING DUCTS | numerical visualization, flow network, turbulent flow, RNG k-e model. | A novel type of heat exchanger with high potential industrial applications is a flow network consisting of mutually intersecting holes in a plate. A series of empirical studies have been conducted to investigate fluid flow behavior in both prototype unit and models using various flow visualization methods such as hydrogen bubble, dye injection, string, particle methods and Laser Doppler velocimetry. In this paper, flows in a pair of intersecting ducts with different intersection angles are investigated numerically using a commercial software called Fluent. The Renormalization Group (RNG) model is used to simulate turbulence behavior in the flow. The numerical visualization technique has successfully revealed turbulent flow characteristics inside the crossing ducts of various intersection angles. The formation of a flow divider and the presence of flow separation regions seen in experiments are confirmed. |
| 66 | R. Camussi, G. Guj, A. Leone | EXPERIMENTAL ANALYSIS OF JETS IN CROSS-FLOW AT LOW AND MODERATE REYNOLDS NUMBER | cross-flows, visualizations, instability, coherent structures, wavelet analysis | Flow visualizations and velocity measurements of jets in cross-flow configuration at Reynolds numbers Rej=250 and 20000, are performed in a water tunnel and a wind tunnel for several jet-to-cross stream velocity ratios (R). In the water tunnel, the flow structures are analyzed by injecting methylene blue and fluorescein both into the jet flow and from injectors at the wall of the principal tunnel. In the wind tunnel smoke visualizations and hot wire measurements are performed. The basic vortical systems and coherent structures are visualized and their characteristics are analyzed. The mechanisms of formation, evolution and destabilization of the ring-like vortices forming from the interaction of the jet with the cross stream, are discussed with particular emphasis to the effects of the R parameter. |
| 67 | Robert Kiml, Sadanari Mochizuki, Akira Murata | INFLUENCE OF 180 DEGREE SHARP TURN ON THE HEAT TRANSFER AND FLOW BEHAVIOR IN A SMOOTH SQUARE CROSS SECTIONAL SERPENTINE CHANNEL | 180 degree sharp turn, tracer method, forced convection, gas turbine blade | The objective of this study is to investigate a heat transfer phenomenon which occurs in a 180 degree sharp turn section of a smooth serpentine channel which represents a cooling passage inside a gas turbine rotor blade. The heat transfer results revealed significant heat transfer enhancements on the Outer and Side walls within the 180 degree sharp turn region and in the 2nd passage. To understand the mechanism of this phenomenon, flow visualization was conducted using the Paraffin mist as a tracer. The flow visualization revealed a strong three-dimensional flow structure due to the 180 degree sharp-turn. The existence of the symmetrical three-dimensional vortices gradually developing in the bend region were confirmed. The mechanisms of the heat transfer in the regions of the 180 degree sharp-turn and at the entrance to the 2nd straight passage were examined in relation to the flow. |
| 68 | N.J. Dam N.M. Sijtsema R.A.L. Tolboom J.J. ter Meulen | RAYLEIGH AND RAMAN SCATTERING USED FOR COMPRESSIBLE FLOW DIAGNOSTICS | non-intrusive diagnostics, density mapping, time evolution | Rayleigh and Raman scattering of UV laser light was used to obtain two-dimensional density distribution maps of supersonic compressible flows. The spatially resolved intensity of both Rayleigh and Raman scattered light is directly proportional to the local molecular density. Therefore, imaging of light scattered by a flow field is a convenient, quantitative and non-intrusive means of obtaining two-dimensional data on the density in a plane through the flow. The use of powerful pulsed laser systems and gated camera systems allows to freeze the flow on a nanosecond time scale and, therefore, also enables to study the time evolution of non-stationary flows. Both Rayleigh and Raman scattering techniques are illustrated by monitoring the periodic density variations in an underexpanded nozzle flow (‘diamond pattern'). Whereas Rayleigh scattering is the more sensitive, Raman scattering can be applied to distinguish between different molecules present in the flow and can be very useful when solid objects are present. |
| 69 | R.H.G. Müller | HELICOPTER ROTOR WAKE VISUALIZATION IN FORWARD FLIGHT | helicopter, wake, rotor, bvi. | The phenomenon of Blade Vortex Interaction (BVI) is a very important problem in helicopter rotor flow. It causes strong dynamic blade loads and impulsive noise emission. For optimization of the rotor flow different numerical simulation methods are being developed. This paper presents visualization data that can be used for verification of those simulation methods. The visualization is conducted by ejecting water/oil vapor at the blade tip of a model rotor. The vapor is absorbed by the tip vortex and the vortex paths are visualized clearly over almost two turns of the rotor wake. The 3-dimensional structure of the wake is reconstructed by using the views of two still cameras in orthogonal arrangement. For the reconstruction the photographs are digitized using a CCD camera and an image analysis system. The skeleton line of the vapor filaments in the digitized images is regarded as the vortex core center and is vectorized manually. Wake data for an advance ratio of 0.1, 0.2, and 0.3 at different flight conditions (regular forward flight, landing approach) are provided. |
| 70 | I Dias M.L. Riethmuller | VISUALIZATION OF THE FORMING BUBBLE AND PIV MEASUREMENT OF SURROUNDING LIQUID USING FLUORESCENT PARTICLES | two-phase flow, bubble formation, flow visualization, shadow detection method, PIV, laser induced fluorescence | A two-phase visualization and measurement technique is used to investigate the injection of air bubbles into stagnant water through a single needle, within the single bubbling regime under constant gas flow conditions. The referred experimental technique couples the sizing of the dispersed phase, using the shadow detection method, with the simultaneous PIV - particle image velocimetry - measurement of the continuous phase seeded with fluorescent particles. The results show the evolution of the liquid velocity around a growing bubble during its formation cycle. The influence of the wake created by the preceding bubble on the first stages of the subsequent bubble formation is also investigated. |
| 71 | Tong-Miin Liou Chung-Chu Chen, Tzi-Wei Tsai | LIQUID CRYSTAL MEASUREMENTS OF HEAT TRANSFER IN A 180-DEG SHARP TURNING DUCT WITH DIFFERENT DIVIDER THICKNESSES | liquid crystal, heat transfer, sharp turn, divider thickness | Flow visualization using a transient liquid crystal method is presented to study the effect of divider thickness on the local heat transfer distributions around a sharp 180-deg turn of a two-pass smooth square duct. Detailed local Nusselt number distributions on the top, blade-tip, and side walls are given for three divider thicknesses, = 0.10, 0.25, and 0.50, at a Reynolds number of 1.2 x 104. Complementary pressure loss measurements are presented in terms of variation of friction factor with . The results show that = 0.25 provides the highest total averaged Nusselt number ratios, both at constant flow rate and at constant pumping power conditions, and a moderate friction factor. |
| 72 | N. Fomin, E. Lavinskaja, W. Merzkirch, D. Vitkin | STATISTICAL ANALYSIS OF TURBULENCE BY SPECKLE PHOTOGRAPHY | speckle photography, turbulence, correlation function, refractive index, shock wave | Both double and single (prolonged) exposure speckle photography are used for statistical analysis of turbulent flows. Using single (prolonged) exposure speckle photography (SPESP), instantaneous quantitative measurement of 2D distribution of turbulence intensity in a flame is performed. Anisotropy of turbulence is visualized by diffraction halo form and quantitatively evaluated by measuring the diffraction halo diameters. Using double exposure speckle photography (DESP), quantitative visualization of the planar distribution of the refractive deflection angles of the light transmitted through the compressible turbulent flow is done. Turbulent structures are visible in the patterns of the deflection angles isolines. The correlation functions of these deflection angles are constructed and analyzed. |
| 73 | D.Vitkin, W.Merzkirch | SPECKLE-PHOTOGRAPHIC MEASUREMENT OF UNSTEADY FLOW PROCESSES USING A HIGH-SPEED CCD CAMERA | speckle photography, temperature field, high speed CCD technique | Planar optical speckle measurements of the temperature in the air around a suddenly heated wire are performed with a high-speed electronic camera. The digital speckle recordings are evaluated by means of an image processing algorithm originally developed for the evaluation of particle image velocimetry (PIV) recordings. |
| 74 | F. T. Van Der Laan, V. C. S. Ferreira, A. W. Elbern | HIGH VELOCITY FLUID MEASUREMENT WITH AN INTRAFRAME PROCESSING IMAGES | particle image velocimetry, images processing, intraframe | This work presents a simple procedure for measuring flow velocity of the order of 100m/s using a digital video camera CCD-DV with variable shutter velocity. This procedure, called Intraframe, treats the image inside a single frame digitised by means of a fast acquisition interface board. A space-temporal algorithm identifies the particles and calculates the velocity. |
| 75 | Walter Borisovich Amfilokhiev, Valeriy Ivanovich Shivelkin, Oleg Borisovich Shylicovsky, Aleksander Aleksandrovich Ponomarjov, Aleksei Aleksandrovich Ponomarjev | NUMERICAL VISUALIZATION OF POTENTIAL FLOWS | potential flow, CAD/CAM systems, designing, optimization, evident display, hydrodynamic characteristics (HC). | In the work the representation of result of hydrodynamic calculations are offered for different classes of the users |
| 76 | Walter B. Amfilokhiev, Andrey S. Guzeyev | STREAM AROUND ISOLATED ROUGHNESS ELEMENT IN THE BOUNDERY LAYER | flow visualization, separate zone, boundary layer, vortexes | The results for flow around an isolated roughness element in the boundary layer at Reynolds number 3.103 - 6.103 are presented. Investigations have been carried out in the transparent working part with cross section 150x150 mm. Colouring fluids, hydrogen bubbles and air bubbles have been used for flow visualization. The isolated roughness element had form of sphere, hemisphere, segment, cone. The pictures of flows in diametrical section of bodies are shown as the results of the investigation. |
| 77 | I.A Znamenskaya, T.A. Gulu-Zade | UNSTEADY 3D FLOW FIELD VISUALIZATION BY IMPULSE VOLUME DISCHARGE | non-stable gas flow; 3-d flow structure; pulse volume discharge; pre-ionization; flow field images; shock waves interactions | visualization by impulse volume discharge was tested and used for investigations of shock wave interactions and some supersonic flows in a shock tube. Special type of discharge was used- volume discharge with ultraviolet preionization by radiation from the sliding surface discharges, That type of discharge proved to be effective for non-stationary 3D flow visualization.The flow field images with shock waves, weak disturbances, vortexes have been obtained with temporary resolution 150 ns, space resolution 0.5 mm. |
| 78 | Mathias Buchmann, Dieter Mewes | MEASUREMENT OF THE LOCAL INTENSITIES OF SEGREGATION WITH THE TOMOGRAPHICAL DUAL WAVELENGTH PHOTOMETRY | micro- and macromixing, laminar mixing, optical tomography | The newly developed tomographical dual wavelength photometry enables the measurement of the local intensity of segregation at a multitude of points inside the stirred vessel. This is done by injecting a mixture of an inert and a reacting dye into the vessel. The inert dye serves as a tracer for the macromixing, whereas the vanishing of the reacting dye shows the micromixing. The concentration fields of the dyes are measured simultaneously by transluminating the vessel from three directions with superimposed laser beams of different wavelength. The light absorption by the dyes is measured with CCD-cameras and these projections are used for the tomographic reconstruction of the concentration fields. Low Reynolds number measurements with a Rushton turbine show better macro- and micromixing for a dye injection closer to the stirrer shaft compared to a position closer to the main vortex. |
| 79 | Karl Bühler | VISUALIZATION OF FLOW STRUCTURES IN ROTATING FLUIDS | rotating fluids, topological flow structure, swirling motion, vortex breakdown, recirculation zone, streamsurfaces, cylindrical geometry, spherical geometry, finite difference method, numerical simulations, streamfunction-vorticity-formulation, experimental realization, fixed and stress-free boundary conditions, flow visualization, black-white and colour pictures | Vortex breakdown phenomena in rotating fluids are investigated both theoretically and experimentally. The fluid is contained in a cylindrical container or a cone between two spherical surfaces. The primary swirling motion is induced by the rotating upper or lower boundary. The upper surface can be fixed with non-slip condition or can be a stress-free surface. Depending on these boundary conditions and on the Reynolds number novel structures of recirculation zones are realized. The axisymmetric flow patterns are simulated numerically by a finite difference method. Experiments are done to visualize the topological structure of the flow pattern and to observe the existence ranges of the different recirculating flows. The comparison of the theoretical and experimental approach have been in good agreement in respect to the topological structure of the flow. |
| 80 | L. Weinstein, W. Culliton, R. Rivers | VISUALIZATION OF TRANSONIC FLOW OVER A T-38 AIRCRAFT | aircraft , Schlieren, flow visualization, transonic flow, shock waves | Flow field images were obtained around a T-38 aircraft flying at transonic speeds. The images were obtained with a schlieren camera mounted on a sun tracking telescope, which uses the edge of the sun as a light source. An electronic Time Delay and Integration sensor is used to record the images. This camera is a unique instrument capable of capturing the flow field images around aircraft in flight. Images were obtained for aircraft distances from 8.6 to 9.6 km, and for aircraft Mach numbers from 0.96 to 1.01. The images are compared to a schlieren image obtained previously for the same type of aircraft at Mach 1.1. The flow field over portions of the aircraft becomes supersonic slightly before the aircraft Mach number reaches 1, so shock waves and expansion flows are seen over the aircraft for this condition. At just over Mach 1, a strong shock forms ahead of the aircraft which appears to be detached. The bow shock is clearly attached at Mach 1.1. |
| 81 | B. J. Pelliccia D. W. Watt | THREE-DIMENSIONAL IMAGING OF TURBULENT FLOWS: OPTICAL TOMOGRAPHY AND PROPER ORTHOGONAL DECOMPOSITION | tomography, shearing interferometry, turbulent jets, proper orthogonal decomposition | A multiple-beam, finite-fringe shearing interferometer, developed for optical tomography of unsteady flows, is described. This instrument is used to investigate the existence of large-scale coherent structures in turbulent flows. Projection data of a round, neutrally buoyant, helium-argon turbulent jet was obtained from six viewing directions. Fourier spectral analysis provided separation of the desired phase from unwanted background irradiance variations. Tomographic reconstruction, using a truncated Fourier-Bessel expansion was performed to obtain the three-dimensional density field. A spatial “snapshot” Proper Orthogonal Decomposition (POD) was applied to examine the three-dimensional structure of the turbulent flow. |
| 82 | Metin Uçak, I . Bedii Özdemir | SUPERSONIC JETS EXHAUSTING INTO TUBULAR CONFINED SPACES | supersonic flow, jets, axisymmetric shear layers, rocket and launcher interactions | This paper describes the characteristics of a supersonic flow in an open-ended tube with emphasis on the shock structures and the resulting modifications in the approaching flow. The jet with a Mach number of 2 and underexpansion ratio in between 1.08 and 1.60 was exhausted from a convergent-divergent nozzle of 20 mm exit diameter into tubes of 35 mm diameter and 150 and 300 mm lengths, at nozzle-to-tube distances varying as 8.1, 0 and 10 mm. The quantities of interest obtained from shadowgraph pictures were included wall and centerline reflection angles and the Mach disc location.The results revealed that when there is not sufficient air entrainment to drive the turbulent mixing inside the tube, the compressibility effects prevail, in that the strength of the reflected shock increases, resulting in a strong normal shock in the vicinity of the centerline. |
| 83 | H. Johari, M. Gharib | NEAR FIELD DEVELOPMENT OF STARTING BUOYANT FLOWS | starting buoyant flows, thermals, plumes | The initial stages of buoyancy-driven flows ejected from cylindrical tubes with length to diameter ratios between two and thirteen were studied experimentally. Density ratios up to 10% were utilised in an aqueous setting. A technique was developed to release the column of buoyant fluid with minimal disturbances during the discharge. Direct flow visualization and digital particle image velocimetry techniques were utilised for the examination of the flow field. A starting vortex ring rolled up near the source at first. The starting vortex ring became asymmetric and disintegrated into a turbulent mass within the first five diameters. This fluid mass then reorganised into a larger, more diffuse thermal. The thermal formation occurred in a shorter distance as the length to diameter ratio of the buoyant column decreased. The temporal evolution of peak vorticity and circulation associated with the buoyant fluid revealed large amplitude oscillations. |
| 84 | Yang Zhang | THE BOUNDARY TRACKING AND ANALYSIS OF LASER TOMOGRAPHIC IMAGES OF TURBULENT PREMIXED FLAMES | turbulent premixed flames, boundary tracking | In this paper, the boundary tracking and analysis of laser tomographic images of turbulent premixed flames have been presented. Semi-automatic boundary tracking method was preferred and adopted for achieving high accuracy and efficiency. Both ensemble averaged and time dependent analyses have been conducted. The turbulent burning velocity of the premixed flames can be derived from an ensemble averaged processing technique. The obtained results agree well with published data which are obtained by other experimental techniques. The time dependent analysis of the boundary length (flame contour length) demonstrates that the impinging flame contours fluctuate at some particular low frequencies. |
| 85 | A.D.Ferreira, A.C.M.Sousa, A.M.G. Lopes, D.X.Viegas | NUMERICAL EVALUATION OF WIND FLOW AROUND BLUFF BODIES | pedestrian comfort, wind around buildings, interference, numerical simulation, Lagrangian visualization | The paper presents data obtained by means of numerical simulation for two types of flow around bluff bodies (flow around an isolated, single structure and flow over several obstacles). The discretization of the differential equations was accomplished with the control volume formulation in a Cartesian coordinate system, and the SIMPLEC procedure was used to achieve the link between continuity and momentum equations. The k-e RNG model was chosen to simulate turbulence effects. The evaluation of the model was performed by comparing the predictions against the experimental results for a square cylinder placed in a channel, and also for a single cube immersed in a boundary layer flow, for different incidence angle values. The model was also applied to a group of several pavilions separated by passageways, placed in the area of the Expo’98 being held in Lisbon, with focus on pedestrian comfort. |
| 86 | Sang-Yong Lee, Seon-Woong Hwang, Jae-Yeol Lee, In-Seop Lee | FLOW VISUALIZATION OF THE LEAKAGE IN THE ROTARY COMPRESSOR | leakage, fluorescence, particle, re-expansion, performance, gap, fanno flow, poiseuille flow, two-phase flow, rotary compressor,vane,roller | The flow characteristics in the cylinder of the rotary compressor are investigated by the visualization experiment. In order to visualize the gas flow, the fluorescence mixed with oil and the 5 micrometer particle are used as the tracer in the cylinder. The red and the blue filters in the camera and illuminator are applied respectively to eliminate other reflections from the metal in the cylinder in case of using the fluorescence(1). The theoretical study is carried out to predict the characteristics of the leakage and compared with experiment(2). The result shows that the leakage flow between the vane and the slot of the cylinder occurs only at some angles, and the velocity, which is normalized by the speed of sound , is about 0.094 when the ratio of the upstream to the downstream pressure is 0.7967(3). Also the leakage at the vane head and the roller head in the cylinder of the compressor is evaluated experimentally. |
| 87 | G.A.J. van der Plas, R.J.M. Bastiaans | ACCURACY AND RESOLUTION OF A FAST PTV-ALGORITHM SUITABLE FOR HIRES-PV | ptv, piv, hires-pv, accuracy and yield | A new Particle-Tracking-Velocimetry (PTV) algorithm has been developed. This algorithm is a first step towards 3D-PTV and a basis for High Resolution Particle Velocimetry (HiRes-PV). The algorithm and its separate components are described and its performance was tested. Particle tracking tests were performed with the algorithm and it was used together with PIV to perform HiRes-PV. The designed algorithm satisfies the high demands on computational speed, storage and accuracy for PTV. Furthermore HiRes-PV results show a substantially increased performance. |
| 88 | Philippe Wernert | ACCURACY OF CLASSICAL CORRELATION AND SUB-PIXEL INTERPOLATION METHODS FOR A BASIC PARTICLE CONFIGURATION IN VIDEO PIV | accuracy, autocorrelation, ccd camera, cross-correlation, particle image velocimetry (piv), sub-pixel interpolation | A theoretical model based on the general principles of Fourier optics and leading to an analytical equation for the image recorded on a CCD camera during PIV experiments is described. Numerical simulations based on this model have been conducted in the most ideal case, i.e. one single particle in an interrogation spot without noise. These simulations lead to statistical results concerning the accuracy of the classical correlation and sub-pixel interpolation methods (center of mass interpolator, parabolic fit and gaussian fit) commonly used in PIV. |
| 89 | Peter Gschwind, Volker Kottke | REGULAR FLOW STRUCTURES IN CHANNELS WITH SYMMETRIC AND ASYMMETRIC WALLS | channel flow, symmetric walls, asymmetric walls, mass transfer, three-dimensional flow | Various ducts with symmetric and asymmetric axis were investigated experimentally for the effects of flow phenomena on the near wall heat and mass transfer. The flow was visualised with a mass transfer method, using ammonia as a tracer gas, chemisorption and coupled colour reaction. The experimental analysis for the flow phenomena and mass transfer in sinusoidal wavy channels was performed for plates with constant length. A regular, three-dimensional flow structure with different flow types can be observed in a number of cases. |
| 90 | M. Gremigni , L. Guidi, A. Nassi | TOOLS FOR THE DIRECT MANIPULATION OF SCIENTIFIC VISUALIZATION MODELS IN VIRTUAL REALITY ENVIRONMENTS | scientific visualization, virtual reality, stereo rendering | The aim of this work is the study and the application of Virtual Reality techniques for visualising the results of fluid-dynamics numerical simulations. The techniques and tools used for the development of the prototype of a visualization code, named VisCFD, are described: possibility for the user to set an approximation of the graphic representation suitable for the quick exploration inside the simulation system (probe dataset); use of virtual objects aimed to facilitate both the spatial localisation and the visualization models manipulation (widgets); stereo rendering by using 3D stereo glasses. This prototype is characterised by a level of ergonomics, interactivity and effectiveness very high, typical of immersive Virtual Reality applications. In spite of this, VisCFD can be executed even on a low-end, UNIX or Windows, workstation and so it is available to the largest number of users. |
| 91 | J.Z. Shu ; H. Ming ; X.H. Sun; M. Bai; G.P. Zhang and Z.C. Liang | A GRIN FIZEAU INTERFEROMETER FOR THE MEASUREMENT OF DEFORMATIO AND OSCILLATION OF FREE SURFACE | interferometry; grin lens;fiber sensor;oscillation;surface wave; thermocapillary convection | A Fizeau interferometer consist of a GRIN (Gradient Index) rod lens and a LD-Pumped single-mode double-frequency Nd:YVO4 laser has been developed. It is simple in construction and easy to be used for the measurement of small free-surface shape, deformation and the free-surface oscilltory features, i.e. the amplitude, frequency and mode, of a liquid phase / or a solid object. The principle of the interferometer and the experimental results are given. |
| 92 | G. J. Hwang, M. H. Lin, C. H. Lin and J. F. Jean | VISUALIZATION OF LONGITUDINAL VORTICES IN CURVED RECTANGULAR CHANNEL | flow visualization, rotating curved rectangular channel, longitudinal vortices | The objective of this study is to visualize the flow patterns in a rotating curved rectangular channel with radius of curvature R=0.6 m. Without rotation, the longitudinal vortices are induced by the centrifugal forces. With rotation, the Coriolis and centrifugal forces drive the longitudinal vortices. In a flow with constant rotation speed, the forward and backward channel walls affect the formation of vortices. The forward channel wall promotes the formation. On the contrary, the backward channel surface drastically reduces the formation of vortices. One uses smoke generated by burning incense powder for flow visualization. The flow speed is near 0.35 m/s. The photographs of cross-sectional flow pattern were taken from the exit of the channel. The photographs of longitudinal flow pattern were taken through side wall. The light sheet emitted from a slide projector is perpendicular to the viewing direction. |
| 93 | Madeleine Coutanceau, Patrick Ehrmann, Nathalie Boisaubert | SOME NEW INSIGHTS ON THE ONSET AND DEVELOPMENTOF THREE-DIMENSIONAL END EFFECTS AND SECONDARY INSTABILITY IN THE WAKE OF QUASI-2D OBSTACLES | forming wakes, semicircular shell, solid semicircular cylinder, circular cylinder, flat plate, three dimensionalities, secondary instabilities, end effects, Taylor-Görtler vortices, particle-streak visualization | Using a classical particle-streak visualization-technique, we analyse the onset and time-development of 3D structures in the wake-flow, forming behind various (hollow at the back or solid) short (5.2 in aspect ratio) cylindrical bodies, limited by endplates, and impulsively set in uniform translation. For this, pictures have been captured in the mid-span section, for 60 Re 600. Clear patterns of Taylor-Görtler vortices have been revealed for Re>200, in the case of a semicircular shell, in addition to the classical end-vortices. Whereas, for the other selected solid bodies (circular, semicircular in reversed arrangements, flat plate), body-end effects appeared to be dominant in the selected Rerange and to delay or even to prevent secondary instability to set up, rendering the wake flow more highly three-dimensional in the whole. |
| 94 | Yu. D. Chashechkin | SCHLIEREN AND COLOUR SCHLIEREN VISUALIZATION OF A STRATIFIED FLOW | stratification, light, dispersion, Schlieren, colour, structure | Description of colour Schlieren visualization techniques is presented. Method is based on natural dispersion of light in a stratified tank. For producing colour schlieren image of a stratified flow an illuminated slit is placed horizontally and regular grating is used as light cutting element in the focal plane of the schlieren device receiving part. The method is characterised by high spatial and temporal resolution and more wide dynamic range than traditional schlieren device with slit and Foucault knife. Examples of traditional black-and-white and colour images of a stratified flow are presented. |
| 95 | L. Riou, J. Fayolle, T. Fournel | P.I.V. MEASUREMENT USING MULTIPLE CAMERAS : THE CALIBRATION METHOD | piv, image processing, camera calibration, stereoscopy, displacement field | A calibration method to accurately determine the transformation matrix relating image coordinates and position in the corresponding, real 3-D space has been developed. The method was applied to images obtained simultaneously from more than one camera. Using the projective matrix it was possible to bring into coincidence vectors obtained from the different cameras and to obtain measurements of the third component of the velocity vector. |
| 96 | J. G. Santiago, S. T. Wereley, C. D. Meinhart , D. J. Beebe , R. J. Adrian | A MICRON-RESOLUTION PARTICLE IMAGE VELOCIMETRY SYSTEM FOR MICROFLUIDICS | particle image velocimetry, piv, velocimetry, fluidics, microfluidics, microelectromechanical systems, MEMS, resolution, Brownian motion. | A micron-resolution particle image velocimetry (micro-PIV) system has been developed to measure instantaneous and ensemble-averaged flow fields in micron-scale fluidic devices. The system utilizes 100 to 300 nm diameter seed particles, an epifluorescent microscope, and an intensified CCD camera to record high-resolution particle-image fields. Velocity vector fields have been measured with spatial resolutions of 6.9 x 6.9 x 1.5 micro m (less than 3.5 micro m between vectors for 50% a overlap of interrogation spots). Spatial resolutions of 1.5 x 1.5 x 1.5 micro m are achievable. Vector field measurements are presented for 70 micro m wide, microfabricated silicon channels and for a glass Hele-Shaw cell with a 5 micro m plate separation. The spatial resolution and accuracy of the velocity measurements is limited by the diffraction limit of the recording optics, noise in the particle image field, and the interaction of the fluid with the finite-sized seed particles. |
| 97 | B.E. Milton, R.D. Archer | BREAK-UP AND ENTRAINMENT OF LIQUID WALL DROPLETS BY WEAK SHOCK WAVES | droplet shattering, liquid entrainment, film entrainment, fuel atomisation | Experiments on the direct entrainment of liquids attached to the walls of a duct into an airstream have been carried out using a shock tube. Weak shock waves have been used to simulate flow velocities in the range 20 to 106 m/s, typical of fuel/air flows in engine induction systems. Droplets located both on the walls and suspended in the centre of the flow have been considered. While the entrainment rate and atomised particle motion is different in the two cases, the break-up process has some similarities. However, the boundary layer effects are still seen to be significant with a paired vortex system drawing off liquid in the form of a cloud structure where it is atomised and distributed to the flow field. The transverse growth rate of the finely atomised droplets across the flow field increases outside the boundary layer region. |
| 98 | S. Miyashiro, A. Mohammadi, K. Miwa, H. Groenig | OPTICAL MEASUREMENTS OF LIQUID SPRAYS WITH NEW NANOSECOND SPARK LIGHT SOURCE | nanosecond spark, shadowgraph, double photography, diesel spray, image analysis | The design and performance of a new low-jitter reliable 12-30 ns spark source are described and the source is first applied for visualization of diesel sprays with use of shadowgraph technique. The photograph is so clear that we can distinguish droplets and discern the diameter and shape varience of droplets, and obtain the relationship between them by using newly developed droplet image analysis method. We used successfully also the double flash technique with this source to measure the velocity and the flight angle of the droplets. |
| 99 | J-P. Estrade, P. Berthoumieu, G. Lavergne, Y. Biscos | EXPERIMENTAL INVESTIGATION OF DYNAMIC BINARY COLLISION OF VARIOUS LIQUIDS | droplet collisions, effect of Ohnesorge number | Droplet collisions of various liquids are studied using a technique that allows accurate measurements of both initial conditions and final results. Measurements are obtained from video recorded images of the whole process visualised thanks to shadowgraphy. Various liquid droplets have been investigated (ethyl alcohol, glycol, benzyl alcohol, 1-Octanol, water, pentane). Results are reported and permit to identify the different types of collision outcomes. Empirical correlations published by different authors predict the occurrence of separation for both low and high impact parameter. They are compared to the present experimental results. A new semi-theoretical transition curve to characterise bouncing transition has been developed and is presented together with experimental data. A new prediction, determining the evolution of the transition curve between reflexive separation and coalescence with liquid properties has been obtained. |
| 100 | Kazuhide Dan | HOLOGRAPHIC WAVE DAMPING BY USING THE VERTICAL CYLINDRICAL PILES AND SQUARE PILES | holography, wave damping, cylindrical piles, square piles | We showed the technique of wave damping in seashore by using the holographic theory in 6th and 7th ISFV. 1), 2) In 6th ISFV we showed that it is calm in the real image region in holography by the numerical holographic analysis of the sea wave diffraction caused by the vertically aligned circular piles and by the experimental analysis using the wave tank. We can decide the piles arrangement according to the holographic theory, for example, we can change a diameter, a distance between piles and a shape of a pile. In 7th ISFV we showed that there is a big wave height zone in the imaginary image region in holography in case of the same piles arrangement as in 6th ISFV. We think that the wave energy increases in the imaginary image region and decreases in the real image region. This means the wave energy balance in the whole region. |
| 101 | Tamotsu Igarashi | VISUALIZATION OF FLOW AROUND A BLUFF BODY CONTROLLED BY A ROD SET UPSTREAM | flow visualization, flow control, drag reduction, heat transfer enhancement, control rod, bluff body, square prism, circular cylinder | Experimental studies on the reduction of drag and enhancement of heat transfer of bluff bodies, such as, a square prism and a circular cylinder in air stream were conducted. To control the flow around the bluff body, a small rod was set upstream of the one. The reduction of the total drag is 40 to 70 % and the overall heat transfer increases by 40 % compared with those without the rod at the optimum configuration. |
| 102 | S Zhong, C. Kittichaikarn, H P Hodson, P T Ireland | VISUALIZATION OF TURBULENT SPOTS UNDER THE INFLUENCE OF ADVERSE PRESSURE GRADIENTS | turbulent spots, pressure gradient, liquid crystal | In this paper, a method of using temperature sensitive liquid crystal to visualize the thermal footprints of turbulent spots is described. It is employed to study the nature and development of spots under the influence of adverse pressure gradients. The lateral spreading angle and propagation rate of turbulent spots are obtained by analysing the colour information displayed by the liquid crystal. Contours of heat transfer rate beneath the spots are also deduced from the temperature data from the liquid crystal. |
| 103 | Ulrich Rist, Kai Müller , Siegfried Wagner | VISUALIZATION OF LATE-STAGE TRANSITIONAL STRUCTURES IN NUMERICAL DATA USING VORTEX IDENTIFICATION AND FEATURE EXTRACTION | vortex identification, feature extraction and tracking, direct numerical simulation, laminar-turbulent transition,L-vortex, hairpin vortices | Vortices play a major role in many flows and an automated technique that reliably identifies, tracks, and possibly isolates vortices offers much promise for flow diagnostics. The presence of vortices in shear layers is one instance where identification using vorticity based identification is difficult. The present study has lead to the development of an enhanced feature identification and extraction algorithm based on the vortex definition proposed by Jeong \& Hussain~\cite{JoHu95} and on feature extraction similar to Silver~\cite{Si95}. The approach has been used in the case of a numerically simulated boundary layer undergoing laminar-turbulent transition. This type of flow field has the advantage of offering structures of increasing complexity in different streamwise regions useful for validation and verification of the approach. |
| 104 | F. Medaerts, D. Puechberty, L. F. Gomes de Castro. | FLAME FRONT VISUALIZATION IN A TRANSPARENT NATURAL GAS ENGINE USING LASER INDUCED FLUORESCENCE | fluorescence, natural gas, flame front, combustion, spark ignited engine | An investigation of the combustion of natural gas was conducted by visualising flame fronts inside a transparent engine’s combustion chamber. Excimer laser induced fluorescence has enabled the discrimination of unburned gases from burned gases, leading to flame front extraction. Images recorded at three crank angles and for three equivalence ratios were analysed yielding to statistical information on the behaviour of flames in engines. The probability density function computed based on 200 flames allowed the calculation of an apparent flame thickness from which an estimate of cycle by cycle fluctuation and spatial flame propagation could be obtained. |
| 105 | B. Renou, A. Boukhalfa, D. Allano, D. Puechberty and M. Trinité | TURBULENT PREMIXED FLAME VISUALIZATION BY HIGH SPEED LASER TOMOGRAPHY AND PIV. | particle image velocimetry, high-speed laser tomography, premixed turbulent flame and Lewis number | An experimental investigation of turbulent premixed, freely-propagating flames in a decaying isotropic turbulent flow is presented. The experiment showed simultaneously the development of the flame front geometry and the flow structures in the fresh gases under varying conditions of turbulence, fuel/air mixtures and equivalence ratio. This present work used an advanced field imaging techniques to measure the temporal evolution of the tangential strain rate exerted by the turbulent cold flow during the flame propagation and its influence on the local flame structure. Interactions between premixed combustion and multiscales of turbulence were shown strongly dependent on the Lewis number defined by the ratio of thermal to mass diffusivities. Measurement of aerodynamical parameters and local flame structures were obtained simultaneously by using high-speed laser tomography and cross-correlation Particle Image Velocimetry. |
| 106 | Krzysztof Cieslicki, Anna Lasowska | PARTICLE VISUALIZATION OF FLOW IN THE AXISYMMETRICAL PERIODIC MODEL OF PORE SPACE AND IN THE REAL POROUS MEDIUM | cubic correction to Darcy’s law, periodic flow, optical homogenisation, pore space, porous medium, flow streamlines, cavity flow | A cubic correction to the linear flow rate prediction of Darcy’s law was investigated in an experimental program where flow visualization observations were made of flow through porous material. The experiments were conducted in axisymmetrical tubes with periodic step changes in diameter and in a coarse grained, unconsolidated porous medium. Experiments consisted of the measurements of flow characteristic with simultaneous visualizations of streamlines. The main objective of the present work was to correlate the predicted behaviour with the detected flow patterns. Particle flow visualization was applied in the research. The method demanded optical homogenisation of the flowing liquid to the model material, as well as the laser sheet of constant thickness to obtain the required visualization plane. |
| 107 | J. M. M. Sousa, C. Freek, J.C.F. Pereira, W. Merzkirch | VISUALIZATION STUDY OF NEAR-WALL FLOW USING A DIC-PIV SYSTEM | flow visualization, near-wall flow, particle image velocimetry | A turbulent boundary layer flow at = 770 is investigated using a DIC-PIV system. The temporal evolution of near-wall structures is recorded for long periods of time, sampled at a frequency of 25 Hertz. Three data sets, covering the wall region up to 300, 200 and 100 wall units, are used to produce a detailed flow visualization of coherent motions. The large number of images in the data sets (3,800 samples) further allowed the computation of reliable turbulence statistics in a flow without homogeneous directions. Hence, mean longitudinal velocity, Reynolds-stresses and cross-correlation coefficient, as well as estimates of eddy-viscosity, are presented here for y+ < 100. |
| 108 | Byron L. Bemis, Gary S. Settles | VISUALIZATION OF LIQUID METAL, ARC, AND JET INTERACTIONS IN PLASMA CUTTING OF STEEL SHEET | plasma dynamics, flow visualization, molten metals, metal cutting and fabrication, thermal cutting, ultraviolet imaging, schlieren imaging | This research concerns the fluid- and plasma-dynamic mechanisms involved in plasma cutting, the first step of which is flow visualization. No previous visualization of the plasma cutting front is known, since it is small, extremely hot, and blindingly bright. Experiments were carried out to image oxygen-plasma cutting of 11-gauge mild steel plate with a 30 Amp plasma torch. After solving some key problems of magnification and illumination, it was observed that dross-free cuts result from a stable expulsion of molten ejecta from the plasma cutting front. High-speed dross was seen to arise from a highly-constrained cutting front combined with the wetting of the kerf edges by the melt. Low-speed dross presented the most complex behavior of all, being a chaotic phenomenon subject to flow bifurcations leading to several metastable states of equilibrium. In most of these states, molten ejecta is pumped to the sides of the cutting front by surface tension forces, where it wets the kerf edges, forming dross. |
| 109 | Catalin Nae | ABEL INVERSE TRANSFORM FOR SUPERSONIC FLOWS | schlieren, image processing, wind tunnel testing, Abel transform, thermography | In this study we present results obtained in an attempt to investigate the flowfield in an axial-symmetrical flow using noninvasive methods like schlieren pictures and infrared thermography. The methods used are based on numerical processing of digital pictures obtained from tests and some mathematical models of the phenomena involved. The step from qualitative investigation to a quantitative analysis is made using a calibration approach and data obtained from special dedicated experiment. The aim of such studies is to provide a reliable method for fast flowfield investigation during test in wind tunnels without using expensive data acquisition systems for complex flow configurations. |
| 110 | F. Schneider, W. Xiong, W. Merzkirch | VISUALIZATION AND MEASUREMENT OF COHERENT STRUCTURES IN HIGH REYNOLDS NUMBER PIPE FLOW | dpiv, pod, coherent structures, air pipe flow | DPIV measurements are performed in the fully developed flow of air through a circular pipe at high Reynolds numbers. Substraction of the time-averaged velocity profiles yields the planar instantaneous distribution of the fluc-tuations. Vortical structures are visible in these distributions. An analysis of the DPIV velocity fields by the method of Proper Orthogonal Decomposition verifies that coherent structures exist even at the chosen high values of the Reynolds number. |
| 111 | M.G.Kuzmin, M.Yu.Nemilova, N.A.Sadovskii, V.E.Mosharov, A.A.Orlov, V.N.Radchenko | LUMINESCENT PRESSURE SENSORS FOR QUANTITATIVE SURFACE FLOW VISUALIZATION | luminescent, pressure sensor, surface flow visualization. | Pressure measurement on the surface of aircraft models plays an important role in wind tunnel testing. The cost of this testing is very large because a specially designed model with numerous pressure taps is required. New, non intrusive optical pressure measurement method - Luminescent Pressure Sensor (LPS) method - can lead to essential reduction in the cost of wind tunnel tests and in aircraft design cycle. Method is based on a phenomenon of deactivation of photoexcited molecules of organic luminophore by oxygen molecules (quenching). Aircraft model surface is covered by Luminescent Pressure Sensor - thin polymer layer, penetrable for oxygen, containing probe luminophore molecules. Exited by appropriate light source the probe molecules may emit light (luminescence) or may lose energy by interaction with oxygen molecules (luminescence quenching). The part of the lost energy is directly proportional to the oxygen concentration and oxygen mobility in the polymer layer. |
| 112 | Z.J. Wu, G.W. Burgreen, D.C. Thomas, K.C. Butler, B.P. Griffith, J.F. Antaki | VISUALIZATION OF FLOW FEATURES IN A MINIATURE AXIAL FLOW BLOOD PUMP USING A LASER-BASED FLUORESCENT PARTICLE IMAGING TECHNIQUE | laser induced fluorescence, flow visualization, axial flow blood pump, turbomachinery, 3D flow structure | As continuous flow pumps become more prominent as long-term ventricular assist devices for heart failure patients, the wide range of conditions under which they must be operated has become evident. This study investigated internal fluid dynamics in a representative miniature axial flow blood pump to identify intrinsic flow features specific to the pump design and those related to operating conditions. Full field visualization of flow features over a full range of operating conditions was conducted using a laser-based fluorescent particle imaging technique. Complex 3D flow fields at the outlet section were observed. The flow fields were well organized at the blade tip while chaotic at the blade hub. At low flow conditions, an annular region of reverse flow was observed within the inlet section. The mapping of fluid dynamic behavior provided an additional and important criterion for determining favorable operating speeds and for design improvements for rotary blood pumps. |
| 113 | R.K. Gottlieb, Z.J. Wu, H.S. Borovetz, and J.F. Antaki. | CALIBRATION OF A LIQUID CRYSTAL SHEAR STRESS SENSOR FOR VISCOUS FLOW | liquid shear stress, sensor, viscous flow | Shear stress is an significant factor in many blood mediated biological responses. In order to further study these reactions, a satisfactory method of elucidating wall shear stress is necessary. Liquid crystal (LC) has been demonstrated to indicate shear stress in air flow, yet erodes in the presence of many liquids. Combining LC with silicone rubber provides a secure base for the LC to reside without obstructing the sensing properties. This paper accounts the initial testing and calibration of a LC shear stress sensor for viscous flow. |
| 114 | Y. J. Chang, Y. T. Hsieh, Y. M. Chen | FLOW VISUALIZATION DURING A WATER FREEZING PROCESS BY HOLOGRAPHIC INTERFEROMETRY | solidification, supercooling, density inversion | This study investigates the transient solidifi-cation process of pure water in a rectangular cavity. Holographic interferometry was used to visualize the flow field on the complete freezing process. Experimental results indicate that the process of freezing pure water can be classified into four stages: (1) the development of supercooling zone in the upper region of a cavity due to density inversion, (2) the growth of dendritic ice in the supercooling zone, (3) the remelting of dendritic ice by hot circulation, and (4) the growth of hard ice. During the initial period of solidification, the impact from supercooling is deeper, and the amount of dendritic ice, which is affected by the appearance time, directly influences the evolution of the solid-liquid interface. In the later period, however, the impact from supercooling diminishes while that from density inversion increases. |
| 115 | Toshitsugu Hara, Koji Arai, Mitsuhisa Ishida. Takasi Yamaura | PROPAGATION OF HEATED AIR CLOUD | heated air cloud, propagation, visualization, air-conditioning | Propagation of heated air cloud was examined experimentally. Air cloud was heated in a box and was injected intermittently from a round hole of the box. It was flown forward as a pulse flow in the ambient air. The heated air cloud was visualized by white smoke. The propagation and the configuration of the cloud were taken by a video camera. It was found the cloud traveled straight and it was less diffused than conventional continuous airflow. The configuration of the air cloud looked like a vortex ring of air slug. It propagated as a soliton or solitary wave. Pressure change when the cloud passed through was also measured. High pressure was detected at the front of the air cloud and low-pressure change was just followed the high-pressure range. It was suggested heated air cloud would be applied to the floor heating for a conventional air conditioner. |
| 116 | Hui Li | VISUALIZATION OF SWIRLING GAS-SOLID FLOW PATTERN IN A HORIZONTAL PIPE BASED ON WAVELET ANALYSIS OF PRESSURE SIGNALS | gas-solid flow, flow pattern, fluctuating pressure, swirling flow, wavelet transform | The wavelet transform is applied to experimental pressure fluctuations in swirling gas-particle two-phase flows in this paper, to identify and interpret flow pattern transitions in both Fourier and physical spaces. From randomlike pressure fluctuations the characteristic of swirling gas-particle two-phase flows can be extracted, and the relationship between the wall pressure fluctuation and the particle flow patterns can be revealed over a two-dimensional time-frequency plane. The distribution of wavelet coefficients exhibits the variance of particle velocities and particle concentrations with time, and the evident branching structures in wavelet coefficients imply that particles have various velocities. At low air velocities, a periodic oscillation appears in wavelet coefficients around 0.5Hz, which may be interpreted by the existence of the dunes along the top of the pipe at nearly const intervals. |
| 117 | S. Polonsky, D. Barnea, L. Shemer | IMAGE PROCESSING PROCEDURE FOR ANALYZING THE MOTION OF AN ELONGATED BUBBLE RISING IN A VERTICAL PIPE | two-phase flow; slug flow; elongated bubble; translational velocity; bubble shape. | A method for the analysis of a sequence of video images is developed in order to study experimentally the motion of elongated bubbles rising in a vertical pipe, especially the flow in the bubble wake. The motion of elongated (Taylor) bubbles in air-water vertical flow is studied by processing consecutive series of digitized video images. The shape of the elongated bubbles, as well as the velocities of the liquid-gas interfaces, are measured for various flow conditions. The results on the bubble propagation velocity are compared to PIV measurements of the velocity distribution in the liquid ahead of the bubble. An oscillatory motion of the bubble top is observed. The frequency and the amplitude of these oscillations are studied as a function of bubble length and water flow rate. The proposed method is a useful tool for studying the motion of elongated (Taylor) bubbles in two-phase slug flow. |
| 118 | P. M. Sforza, F. Y. Wang | FLOW OVER SURFACE-MOUNTED DOMES AND BLOCKS | obstacle wake, trailing vortices, building downwash, surface flow | Interaction between boundary layer flow over a surface and a body mounted on the surface forms a bubble-like region around the body, called a cavity, in which recirculating flow dominates and turbulence levels are high. Downstream of the cavity a wake develops wherein the flow slowly readjusts to its undisturbed state. Cavity size and shape obtained from flow visualizations are often used to characterize surface-obstacle flows in wind engineering studies. |
| 119 | C. M. Casciola, G. Amati | HELICITY STRUCTURES AND INTERMITTENCY IN A CHANNEL FLOW | coherent structures, wall-bounded flows, intermittency, helicity | Statistical properties of turbulent wall-bounded flows are strictly related to coherent structures. In particular, a recent analysis in terms of Extended Self-Similarity of low Reynolds DNS data shows that structure functions of wall-bounded turbulence exhibit scalings and manifest an increased intermittency towards the wall. To complement the statistical approach, in the present paper flow visualizations obtained from the same data set are discussed. Eduction techniques based on (certain topological) invariants of the velocity gradient tensor are used to extract the structures of vorticity. These are compared with structures of energy dissipation and helicity. In particular, the role of helicity is discussed at length as the possible source of the increased intermittency observed in the wall region. |
| 120 | S.R.N. De Zilwa and J.H. Whitelaw | VISUALIZATION OF JETS INCLINED TO A CROSSFLOW | jets-in-crossflow, two-phase flow, laser-sheet visualization, oil-plate visualization. | Experiments have been performed to evaluate the trajectories and cross-sections of single- and two-phase jets issuing at an angle into a crossflow of air, at Reynolds numbers which imply turbulent flow, and include visualization and measurements of velocity. Detailed measurements were made with jet-to-crossflow velocity ratios of 5 and 10, and angles of inclination between the two flows of 300 and 600, and the two-phase jets were laden with nominally 40 micro m and 80 micro m particles, with a mass loading between 0.1 and 0.4. The visualization techniques were oil-plate and laser-sheet visualization and the single-phase and particle-laden jet velocities were measured by laser- and phase-Doppler velocimetry The results show the penetration of both single-phase and particle-laden jets into the crossflow increased with the velocity ratio and angle of inclination between the jet and crossflow. |
| 121 | R. H. Page, J. Seyed-Yagoobi, and V. Narayanan | FLOW VISUALIZATION OF IMPINGING JET FLOW FROM INNOVATIVE NOZZLES | jet impingement, reattachment, thermography | Impinging jets are widely used in industries to heat, cool, or dry substrates. The research program at Texas A&M University Drying Research Center involves the study of innovative impinging jets aimed to enhance the transport characteristics of conventional in-line and slot jet nozzles. Infrared surface thermography technique is used to obtain a qualitative as well as quantitative measure of the performance of various impinging nozzles. This paper provides an overview of our reattachment nozzle research, and will focus mainly on a two dimensional submerged reattachment nozzle, namely the Slot Jet Reattachment (SJR) nozzle. The flow structure of the SJR nozzle is compared to slot jet nozzles. Flow field of the slot jet and SJR nozzles are visualized by means of laser sheet imaging. Time lapse drying video using infrared camera demonstrates the effectiveness of the 0o exit angle SJR nozzle over the slot jet nozzle under identical peak surface pressure criterion. |
| 122 | Serhat Akin and M.R. Birol Demiral | APPLICATION OF COMPUTERISED TOMOGRAPHY TO THE DETERMINATION OF THREE PHASE RELATIVE PERMEABILITIES | computerised tomography, three phase relative permeabilities | Three phase saturation images along a Berea core plug were obtained in an experimental study using a computerised tomography (CT) scanner. The objective was to obtain images showing how oil and water flowed together with gas in a porous medium. A black oil simulator, coupled with a global optimisation code (simulated annealing) was then used to estimate three phase relative permeabilities and capillary pressures simultaneously. Experimental saturation profiles, differential pressure and recovery data were measured and incorporated in the simulator. Heterogeneity was considered in the simulations by using CT derived porosity values along the core. It was observed that, brine isoperms were linear indicating that the brine relative permeability was a function of its own saturation. It was also noted that two phase and three phase relative permeability data coincided. Three phase oil isoperms were concave, towards the 100% oil apex, indicating higher oil relative permeabilities when both gas and brine were present. |
| 123 | A. E. Corlett | VISUALIZATION OF MULTIPHASE FLOWS USING ELECTRICAL CAPACITANCE TOMOGRAPHY | electrical capacitance tomography, multiphase flow | An experimental study was performed to evaluate the suitability of using an electrical capacitance tomography (ECT) system to visualise two and three component mixtures of crude oil, water and gas. The performance of the ECT system was examined over a wide range of multiphase flow conditions and regimes. For the three phase tests, a range of water cuts between 5% and 90% were used. The flow visualizations from the tomography system were compared with the images filmed using a CCD camera aligned with a Perspex pipe section. Results indicated that ECT was most successful in flow pattern identification when the water cut was less than approximately 50%. However, slug and stratified regimes could be identified at higher water fractions. System calibration and the reconstruction scheme used were critical factors in the quality and reliability of the generated image. |
| 124 | G.V.Dreiden, I.V.Semenova | UNDERWATER SHOCK WAVE REFLECTION FROM SOLID OBSTACLES | shock waves, liquid/solid interfaces, holographic interferometry | The paper presents some experimental results and calculations showing how the solid/liquid interface can affect the behavior of an underwater shock wave. We studied both the cases of regular and irregular reflection (the latter being represented in the formation of lateral waves), as well as the process of shock wave focusing (along with lateral wave formation) caused by its reflection on the concave surface. |
| 125 | J. Fayolle, L. Riou, L. David, J.P. Schon | THE GRID TURBULENCE : MEASUREMENT OF THE DECAY RATE OF THE TURBULENCE INTENSITY WITH IMAGE PROCESSING ALGORITHMS | piv, turbulence intensity, decay rate, grid generated turbulence, direct cross correlation, Fourier cross correlation displacement identification | Particle Image velocimetry methods (PIV) were used to measure the decay of grid generated tur-bulence in a laboratory experiment. The methods used for image analysis were classical cross cor-relation based either on Fourier’s techniques or on direct calculus, and an original algorithm la-belled « displacement identification ». In both cases, the results are in good correspondence with previous studies conducted elsewhere using invasive techniques. The cross correlation based on direct calculus was found to provide data which less accurately measured the decay rate. |
| 126 | J. Fayolle, L. Riou, N. Levy | APPLICATION OF ADVANCED IMAGE PROCESSING TOOLS TO THE CHARACTERIZATION OF DIESEL JETS | diesel jet, image processing, wavelet transform, displacement field, edges, penetration speed, solid angle, diffusion of the jet | Image processing was used to measure the penetration speed of a diesel jet, the solid angle made by the jet near the injector and the percentage of the diffuse part inside the diesel cloud in a combustion chamber pressurised at 30 bars. The image processing tools are based on the properties of a space-scale transform namely the wavelet transform. This transform is applied to the images to determine feature points along the cloud edges which are then tracked over the sequence. In this way, the displacement field of the cloud edges between two successive frames is determined allowing the penetration speed of the jet nozzle and the solid angle of the jet near the injector to be measured. The percentage of the diffuse zone inside the mixture is obtained thanks to the multiscale characterisation of cloud edges. |
| 127 | Hani H. Nigim and Hide S. Koyama | SMOKE-WIRE FLOW VISUALIZATION IN FLOW-FIELD BEHIND A PROPELLER | smoke wire, visualization, propeller | The smoke-wire visualization technique is used in qualitative and quantitative measurements in the flow-field behind a two-bladed propeller. Smoke patterns are recorded with photographic equipment. Experiments are repeated at various rotating speeds ranging from 1500 to 5000 rpm. The results reveal the the tip vortex formation mechanism and the reverse flow in the outer region of the flow-field. The relative size of the vortex core grows as it traverses the axial direction of the wake. Also, a strong deflect in the flow directly behind the blades are observed. |
| 128 | F. Idda, J. Quinard | ACOUSTIC INSTABILITIES SUSTAINED BY ANCHORED FLAMES | anchored flame, premixed flame, flame stability, acoustic instability, pressurefluctuations | Thermo-acoustic instabilities sustained by anchored premixed flames are studied experimentally. The resonant frequencies are well describred by classical modelisations but many mechanisms can contribute to the development of the instability. Light refraction and tomographic imaging are used to study the deformations of a V-flame in the presence of acoustic oscillations. It is shown that strong resonances, higher than 150 dB, are related to the formation of pockets and can eventually induce a Rayleigh-Taylor instability. |
| 129 | M. Maurizot, P. Bouthemy, B. Delyon, L. David, A. Texier. | FLOW TOPOLOGY DETERMINATION BY IMAGE PROCESSING | topology, image processing, linear motion models, unsteady flow, singular point | This paper is concerned with the spatio-temporal analysis of 2D fluid motion from images. The interpretation of such deformable 2D flow fields can generally be stated as the characterization of 2D linear motion models provided that first order approximations are considered in an adequate neighborhood of the so-called singular (or critical) points where the velocity becomes null. Images derived from experimental visualization with the purpose of studying physical phenomena in fluid mechanics such as turbulent flows, were considered. In particular, the flow behind an elliptic cylinder was examined by means of particle streak velocimetry (PSV). Experimental singular point locations were compared to estimated locations with the automatic numerical image processing scheme developed for the study. |
| 130 | Wei Xiong, Wolfgang Merzkirch | VISUALIZATION OF THE NEAR FIELD DOWNSTREAM OF FLOW CONDITIONERS | piv, disturbed pipe flow, double bends, flow conditioner | Visualization of the near field downstream of three different flow conditioners, a tube bundle and two perforated plates, was investigated by measuring the axial velocity component with Particle Image Velocimetry (PIV). The conditioners were exposed to the flow disturbed by a 900 out-of-plane double-bend. These experiments were performed in the air flow through a pipeline of 100 mm i.d. at Reynolds numbers between 100 000 and 150 000. The different performance of the conditioners investigated can be explained with differences of the flow structure in the near field of these devices, as it becomes visible in the instantaneous 2D velocity distributions obtained with PIV. |
| 131 | U.B. Lackermeier C. Rudnick J. Werther A. Bredebusch H. Burkhardt | VISUALIZATION OF FLOW PHENOMENA INSIDE HIGHLY CONCENTRATED GAS-SOLID FLOWS BY MEANS OF LASER SHEETS | visualization, laser sheet, digital image processing, gas-solid flow, circulating fluidized bed, cluster | In the present paper an attempt has been made to use the laser sheet method inside a circulating fluidized bed (CFB) which is a highly concentrated gas-solid flow with solids volume concentrations in its upper dilute region ranging from 0.1 to 1 vol.-%. The high-speed video technique in combination with the laser sheet technique is applied for the visualization of local flow structures inside a CFB. Since it is not possible to penetrate from outside into this flow with a laser sheet, an endoscope is used to guide the laser light into the fluidized bed. Particles or loosely packed agglomerates passing the illuminated light sheet area reflect the laser light. This provides the possibility for an undisturbed observation of local flow pattern via an endoscope. Digital image processing is applied successfully to pre-process the obtained image sequences and gain a deeper insight into the observed flow structures. Using specific image processing methods shapes and velocities of the flow structure can be calculated. |
| 132 | I Grant, M Mo, X Pan, P Parkin, J Powell, H Reinecke, K Shuang, F Coton, D Lee | OPTICAL EVALUATION OF THE WAKE CHARACTERISTICS OF A WIND TURBINE AND THE PRESCRIBED WAKE MODEL | piv, lsv, prescribed wake, wind-turbine, wind-tunnel |
The complex
flow regime and challenging measurement problems encountered
in the wake of a horizontal axis wind turbine make the obtaining
of a conceptual and qualitative picture of the fluid motion difficult.
The present paper describes a two-part study of wake dynamics in which wake behaviour and the effect of wall interference on wake development were considered. In the first part of the study PIV and laser sheet visualisation (LSV) techniques were used to investigate the deflection of the vortices trailing from blade tips of a small, commercial wind turbine under various conditions of yaw and blade azimuth. The visualsation data was animated in order to aid interpretation of the wake behaviour by examining fixed yaw and variable yaw conditions. In the second part of the study similar techniques were used in a different facility with a wind turbine specifically built for the project. The results obtained in the second experimental study were compared with the predictions of a prescribed wake model and will be used in the method’s further development. |
| 133 | P. J. Disimile, N. Toy, F. Savory | LIQUID CRYSTAL SHEAR FLOW MEASUREMENTS WITHIN A YAWED CAVITY AT MACH 2 | shear stress, liquid crystals, cavity flows | An experimental investigation was undertaken to examine the surface shear flow distribution within an open cavity at M = 2 due to the effect of changing approach flow yaw angle. A rectangular cavity with a length-to-depth ratio of 2 and a planar aspect ratio of 11.79 was positioned within a turbulent boundary layer.. Full field surface shear flow data were provided by the colour change of liquid crystals for nineteen different yaw angles. The information gained from this image analysis was then compared to some previous measurements of the sound pressure levels obtained within the cavity in order to explain the possible cause of the changes in the levels as the cavity is yawed. |
| 134 | M.R.Shaalan, K.A.Elshorbagy, R.M.Kamal | IMPINGEMENT EVAPORATION OF A SURFACE LIQUID DROP | evaporation-surface drop-mass transfer-impingement flow | In the presence of an air stream, a surface water drop on a horizontal flat plate may be unstable to small disturbances. Such air stream exists at the wall jet region developed due to the Impingement of a two-dimensional plane jet on the flat plate. An experimental investigation, utilizing flow visualization techniques beside direct measurements ,was conducted to recognize the physical hydro-mass transport regimes associated with plane jet -surface drop Interaction. the hydro- dynamical physical regimes of a surface drop exposed to an air stream are found to be the semi-stagnant drop,the wave generation history, backward followed by foreward drop edge dislodging ,and finally the complete drop ejection .Mass-transport regimes are found to be the linear evaporative drop, which consumes approxiamately 85% of the total evaporation time, followed by thin film shrinkage in the remainder time.Such shrinkage regime differs in location from hydro-dynamical regime to another. |
| 135 | S. S. Shy, K. L. Gee, and E. I. Lee | THREE DIMENSIONAL MEASUREMENTS OF FINE SCALE STRUCTURE IN AN AQUEOUS VIBRATING-GRIDS TURBULENCE | vibrating-grids turbulence, 3-d lif fine scale measurements, scalar dissipation rate field | A high-resolution, high-speed successive planar laser induced fluorescence imaging of a synchronized swept laser beam, combined with a fast image processing system, similar to that developed by Dahm et al. (1991), is applied to measure three dimensional conserved scalar field in an aqueous zero-mean-shear turbulent flow generated by vibrating-grids. Each measuring image (1 cm x 1 cm) contains 256 x 256 pixels of which the measurement resolution reaches down to the local strain-limited molecular diffusion scale of the flow. Thus we can directly differentiate the resulting scalar field data to obtain the scalar energy dissipation rate field. |
| 136 | Mauro Darida, Ladislav Smrcek | WING GLOVE SURFACE FLOW VISUALIZATION FOR AEROFOIL DESIGN | surface flow visualization, aerofoil, wing glove | Surface flow visualization was conducted to evaluate the flow around an RPV wing/glove combination. The wing is part of an RPV (Remotely Piloted Vehicle) which the Department of Aerospace Engineering at the Glasgow University intends to use as a flying laboratory for laminar aerofoil research. The wind tunnel tests used three glove endplates configurations and a wing extension to obtain flow visualization data and to study the crossflow over the glove surface, particularly near its mid section. Resulting patterns suggest that crossflow over the glove surface is negligible if endplates and a wing extension are fitted. |
| 137 | Baranski Jacek, Blasiak Wlodzimierz, Stasiek Jan | RGB COLOR SPACE ANALYSIS FOR COMBUSTION DIAGNOSTICS AND COMBUSTION CONTROL | rgb color space, image processing, flame analysis | An inexpensive colorimetric analysis of flames has been developed, which is able to measure combustion conditions. In the present work the quantitative expression of flame color without relying on human visual sensation and its utilisation in combustion diagnostics and combustion control have been investigated. Also the sodium inversed D-line technique is to be adopted for calibration of colorimetric technique. |
| 138 | Gary S. Settles, James D. Miller, Thomas J. Hartranft, and Aaron D. Brandt | VISUALIZATION AND COLLECTION OF OVERSPRAY FROM AIRLESS SPRAY PAINTING | spray painting, liquid atomization and sprays, non-Newtonian fluids, environmental engi-neering, pollution control, two-phase flows | Spray painting generates serious airborne pollu-tion through “overspray”, the fraction (typically 50% or more) of the paint which fails to reach its target. This paper examines the phenomenology of “airless” spray painting by flow visualization, and shows how the knowledge thus gained can be used to capture the overspray efficiently near its source. Results show that the airless spray painting process combines the fluid-dynamic phenomena of wavy-sheet breakup, spray en-trainment, spray impingement, inertial droplet impaction, and the turbulent wall jet. In view of this, the paper considers how the overspray-containing wall jet might be induced to separate, roll up, and be drawn away in a particular direc-tion where it can be filtered to remove the over-spray particles. The design of an aerodynami-cally-correct overspray collector results from these considerations. |
| 139 | L. Brahmi, L. David, T. Vietoris, J.L Torero, P. Joulain | EXPERIMENTAL OBSERVATIONS ON THE EFFECT OF PARTIAL FUEL INJECTION ON A LOW VELOCITY REACTING FLOW | partial injection, boundary layer, Emmons problem, combustion | An experimental study of the flow structure above a porous gas burner is conducted to determine the effect of fuel injection on a low velocity air flow and the subsequent effect on the structure of a laminar diffusion flame. The free stream velocity is adjusted to keep the Reynolds number below 800 and the fuel injection velocity is kept below 10 mm/s. Particle Image Velocimetry is used to determine the velocity fields. Flow visualization with a laser sheet and independent seeding of fuel and oxidiser is used describe the nature of the mixing zone. It was determined that under the present conditions injection results in separation of the free stream leading to three distinctive zones, a zone where only fuel is present and characterized by the injection velocities. A mixing zone characterized by a strong acceleration and a third zone that corresponds to the free stream where there is only oxidizer. . |
| 140 | Y. Bailly, P. Speck, J.P. Prenel | VISUALIZATION OF ACOUSTIC PHENOMENA AT THE OPENED END OF A RESONANT DUCT | acoustic, tomograph, streaming, duct | The problem of the sound propagation in a viscous and heat conducting gas contained in a rigid cylindrical duct is classical. Many authors published approximate solutions obtained either in an explicit form from simplified equations or through a numerical process. The assumption that the data at the both ends of the duct are harmonic functions with respect to time is often made ; similarly, the transient part of the solution is generally neglected. These simplifications lead to important differences between model predictions and the reality especially if one of the duct ends is opened. In this paper, an original experimental technique is proposed to investigate acoustical streaming phenomena that take place at the opened end of a resonant duct. We show particularly how flow visualization techniques complete basic acoustic experiments usually based on pressure sensors (microphones). The results of visualizations are performed by using an image processing software to measure geometrical parameters. |
| 141 | Hiroshi Ohue, Genshi Kawashima and Wen-Jei Yang | VISUALIZATION OF COLD THERMAL PLUMES INDUCED BY A ROTATING COLD SURFACE | tracer method, liquid crystal thermography, cold thermal plume, rotating cold surface | Basic experiments were conducted on the cooling of liquid in a cylindrical vessel by a cold surface rotation on the liquid surface. Two visualization experiments, a tracer method and a liquid crystal thermography, were performed. The rotating speed and the test liquid were varied to discuss the effects of rotation and viscosity on both the diffusion of cooled liquid and the development of cold thermal plume. |
| 142 | D. Igra and K. Takayama | EXPERIMENTAL AND NUMERICAL INVESTIGATION OF STRIPPING TYPE BREAKUP ON A CYLINDRICAL WATER DROPLET | droplet, holographic interferometry, numerical simulation,shock wave | The stripping type breakup of a cylindrical water droplet was investigated experimentally and numerically. Experiments were conducted in a shock tube equipped with double exposure holographic interferometery. Cylindrically shaped water droplets of 4.8 mm dia. and 4.0 mm in height were formed in a 4 mm x 150 mm cookie cutter section of a 60 mm x 150 mm shock tube. The shock wave Mach number was 1.47 in atmospheric air. The corresponding Weber and Reynolds numbers were 3,978 and 71,000, respectively. From sequential interferograms, isopycnics inside the droplets were quantitatively observed and effect on their breakup up was discussed. A numerical simulation was carried out by using the CIP method which is useful for shock wave interaction in multi-phase media. |
| 143 | Henryk Szewczyk, Krystyna Jezowiecka-Kabsch, Zdzislaw Bechtold, Anatolij Grigoriew, Wieslaw Wêdrychowicz | VISUALIZATION OF FLOW THROUGH A PIPE WITH AN ORIFICE | flow through a constriction, flow visualization, hydrogen bubble technique | In the paper the authors describe the visualization method, which was used to determine the velocity field patterns in selected zones of flow through a pipe with an orifice built into it. The hydrogen bubble method of visualization used in the investigation, combined with video recording, computer processing and image printout, allows for not only qualitative but also quantitative evaluation of flow phenomena in constricted tubes. The paper discusses the images mapping instantaneous stream shapes, which enabled to determine the length of the recalculation zones. |
| 144 | Shigeaki Inada, Tsuyoshi Taguchi, Wen-Jei Yang | VISUALIZATION OF FIN-SPACING EFFECTS ON NATURAL CONVECTION INSIDE A HORIZONTAL FLUID ENCLOSURE | natural convection, fin spacing, fluid enclosure | Enhancement of natural convection heat transfer in a horizontal fluid layer is an important problem pertinent to suppression of thermal stratification inside low-temperature liquid storage tanks. The experiments are carried out with an air layer between horizontal plates of aspect ratio 8.4, of which the top surface is isothermally heated, the upper surface is cooled at a constant room temperature and the vertical side wall are adiabatic. Some visualized results are reported of flow and temperature fields induced by natural convection in a horizontal fluid layer of finite extent, the former is measured with the laser light sheet methods and the latter with the holographic interferometry. The isothermal patterns and flow patterns were determined from numerical calculations based on a two-dimensional model of the rectangular perpendicular surface within the horizontal fluid layer under the same conditions as those used in the actual experiments. |
| 145 | Hui Li | FLOW STRUCTURE IDENTIFICATION OF A TURBULENT SHEAR FLOW WITH USE OF WAVELET STATISTICS | eddy, jet, turbulence, wavelet auto-correlation analysis, wavelet transform | In identifying the spatial turbulent structure and its evolution in time, the wavelet auto-correlation analysis, which was proposed by author, was employed to analyze the velocity fluctuations in a plane turbulent jet at various positions with help of the complex wavelet function. The wavelet auto-correlation function can extract the most essential scales governing the self-similarity features of eddy motions in terms of period and time delay, which is lost if using traditional statistics methods. It is found that the wavelet auto-correlation function using the Morlet wavelet illustrates better localization in frequency space than that of the Mexican hat wavelet. . |
| 146 | Cheng-Hsiung Kuo Shr-Hau Huang | SHEAR LAYER CHARACTERISTICS OF CAVITY WITH DIFFERENT BOTTOM SLOPES | cavity flow, shear layer instability | The influence of the bottom slope on the self-sustained oscillation across the cavity is studied experimentally by flow visualization and LDV velocity measurement. It is found that significant negative-slope of the bottom of the cavity will modify the abruptness of the velocity profile from the boundary-layer type to the shear-layer type. Thus, the oscillatory characteristic of the shear layer is altered. On the other hand, while the bottom slope of the cavity becomes largely positive, the strength and the upstream extent of the feedback are changed. Therefore, the shear-layer oscillation is changed accordingly. Furthermore, the negative bottom slope can be more effective than the positive one to suppress the self-sustained oscillation within the cavity. |
| 147 | Cheng-Hsiung Kuo J. K. Hsieh | FLOW STRUCTURE OVER AN OSCILLATING AIRFOIL DURING VORTEX/AIRFOIL INTERACTION | vortex/airfoil interaction, oscillating airfoil | During the vortex/airfoil interaction, qualitative flow visualization and quantitative LDV velocity measurements study the unsteady vortical structures over the airfoil. The NACA 0012 airfoil, pivoting at C/3, oscillates within the light stall angle of attack ( ) at high reduced frequency. The incident vortex is controlled to incidence on the airfoil at different phases during the oscillation cycle. The modified phase-averaged technique is employed to evaluate the temporal variations of the local circulation upstream and downstream of the airfoil within the oscillation cycle. It is found that the flow structure over the airfoil is very sensitive to the phases that the incident vortex incidences on the leading edge of the airfoil. This leads to different types of vortex/airfoil interaction. Different types of vortex/airfoil interaction do not affect the formation and subsequent shedding of the trailing vortex during the oscillation cycle. |
| 148 | M. Sell M. Treiber C. Casciaro G. Gyarmathy | AN INTEGRATED VISUALIZATION SYSTEM FOR THE DISPLAY AND ANALYSIS OF EXPERIMENTAL AND NUMERICAL DATA SETS IN TURBOMACHINERY FLOW FIELDS | turbomachinery, cfd validation, secondary flow, unstructured meshes | This paper considers the development of a graphical display tool for the combined presentation of experimental and numerical data sets in turbomachinery flow fields. The underlying objective of the work is the validation of Computational Fluid Dynamics (CFD) codes by detailed measurement, and the experimental investigation of the secondary and loss producing phenomena within turbine blade rows. To validate tools for design it is necessary to compare numerical results with well posed and measured data sets. The visualization package presented in the paper permits the experimental results to be compared and contrasted with the numerical simulations in a consistent manner. Particular weight is placed upon handling the two dimensional data sets generated by the experimental campaigns in an equivalent manner to the fully three dimensional data sets generated by the CFD simulations. |
| 149 | G.M. Zharkova, V.P. Fomichev, S.V. Khaidarov, V.N. Kovrizhina, S.S. Pravdin | FLOW VISUALIZATION IN A DIAMETER DISK PUMP | visualization, disk pump, liquid-crystal thermography, tracing particles | The study of the flow structure in the diameter friction disk pump and the temperature distribution on the disk are the subjects of this paper. Two optical techniques have been realised to visualise the flow structure and the temperature distribution in a diameter friction disk pump. The visualization of the flow pattern was performed by introducing aluminium powder into the water flow in a flume. The Liquid-Crystal (LC) Thermography was used to measure the temperature distribution over the radius of a rotating disk heated over the radius for different angles. The analysis of LC thermography data permitted us to detect the stagnation region where the heat transfer between the disk and air is negligible. |
| 150 | Masakazu Tatsuno, Satoru Maekawa, Hajime Amamoto, Koji Ishi-i and Takashi Karasudani | FLOW AROUND TWO CIRCULAR CYLINDERS IN A TANDEM ARRANGEMENT AT THE CRITICAL REYNOLDS NUMBER REGIME | two cylinders in tandem, critical reynolds number, drag, lift, laminar separation bubble | The aerodynamic interference between two circular cylinders in a tandem arrangement has been examined over the Reynolds number range 105 to 5×105 . The static pressure distributions around the circumference of each cylinder were measured and the drag and lift forces were obtained for each cylinder. Over a small range of Reynolds number at the critical regime, a laminar separation bubble is formed on one side only of the upstream cylinder and this range becomes large with decrease of the spacing between two cylinders. The surface flow patterns were visualized by means of surface oil-flow method. |
| 151 | Ichiro Kimura Atsuhiko Hattori Yasuaki Kuroe Akikazu Kaga | ESTIMATION OF FLOW VELOCITY VECTOR FIELDS USING NEURAL NETWORKS | quantitative flow visualization, piv, velocity vector estimation, neural network, image processing | This paper proposes a new method which uses an artificial neural network for estimating the whole flow velocity vector field from measured velocity vectors. The neural network is trained by using measured velocity vectors as teaching data so that the derivatives of a certain scalar function agree well with the measured data. The continuity equation of flow is consequently satisfied in the vector field estimated by the network and the scalar function gives the stream function. The merit of this method is that measured data on velocity vectors are automatically corrected and the estimated data satisfy the continuity equation of flow. The pattern of streamlines is additionally obtained from the output of the network. |
| 152 | M.Kurosaka | SPIRALING SHEAR LAYER AS A CAUSE OF VORTEX BREAKDOWN | vortical flows, laser induced fluorescence | A formation mechanism of vortex breakdown is proposed based on a transient process . The argument is supported by (1) visual evidence of straight, in-line alignment of the spiraling shear layer within the vortex core, (2) a consideration of the constraint imposed by the externally swirling flow, and (3) self induction between spiraling shear layers. |
| 153 | Jeff Parsons, Marcelo Garcia | QUANTIFICATION OF THE SECONDARY INSTABILITIES IN A GRAVITY CURRENT FRONT | gravity current, instabilities | The effects of scale on the appearance and dimensionless quantities of a gravity current front have been well-documented [1,2]. These effects manifest themselves as higher dimensionless mixing rates, increasing the transport capacity of these flows. Though the fronts in earlier experiments [3] appeared turbulent, some important features of the flow were extremely small and could have been susceptible to viscous effects. Typically, in energetic flows like those discussed here, viscous forces become dominant as length scales tend towards the millimeter range and velocity scales approach the millimeter per second range. These length and time scales, when buried in the midst of a large (order of meters), energetic (TKE > 5 cm2/s), transient flow, are extremely difficult to characterise and quantify with traditional fluid mechanical techniques. |
| 154 | O. Feldmann, F. Mayinger | SHORT-TIME HOLOGRAPHY APPLIED TO THE THREE DIMENSIONAL TWO-PHASE FLOW IN AN AERATED, STIRRED VESSEL | short-time holography, Image processing, two-phase flow, aerated stirred vessel | The present paper deals with the application of the short-time holography to the analysis of the three-dimensional two-phase flow in a aerated, stirred vessels. Both, the macroscopic structure of the flow, such as the flow field of the generated bubbles, and its microscopic structure, such as the number, the size, the location, and the velocities of the generated bubbles were investigated. Two holograms of the volume of interest, the entire agitator-vessel, were taken simultaneously from two viewing directions which were perpendicular to one another. The developed holograms are reconstructed, and stationary images, the real images of the recorded scene, are formed three-dimensionally in front of the holographic plates. These two 3D reconstructions of the flow field, seen from different viewing-directions, were scanned by means of CCD-cameras. Computer based algorithms were developed in order to determine the quantities to be measured that are stored in the obtained video-images. |
| 155 | Yao Mathias Gbamele, Philippe Desevaux, Jean-Pierre Prenel | APPLICATION OF THE POLYCHROMATIC LASER TOMOGRAPHY TO PARTICLE STREAKING VELOCIMETRY TECHNIQUE | particle streaking velocimetry, polychromatic laser tomography, 2D and 3D flow visualization. | A flow visualization technique intended to improve the quality of frames processed in Particle Streaking Velocimetry (PSV) is applied to a hydrodynamic flow. This technique is based on the generation of several adjacent laser light sheets, which have different wavelengths with a homogeneous power density distribution. It allows the validation of two-dimensional or three-dimensional flows configuration before applying an image processing. In the case of sharply three-dimensional flows, the velocity vector direction is obtained. Limiting parameters of this technique are investigated. |
| 156 | David F. Fisher, Daniel G. Murri | FOREBODY FLOW VISUALIZATION ON THE F-18 HARV WITH ACTUATED FOREBODY STRAKES | aircraft, F-18, flight, flight test, forebody, flow visualization, smoke, strake, vortical flow, vortex | Off-surface smoke flow visualization and extensive pressure measurements were obtained on the forebody of the NASA F-18 High Alpha Research Vehicle equipped with actuated forebody strakes. Test points at angle of attack (aaa)=50 deg were examined in which only one strake was deflected or in which both strakes were deflected differentially. The forebody pressures were integrated to obtain forebody yawing moments. Results showed that small single strake deflections can cause an undesirable yawing moment reversal. At aaa = 50 deg;, this reversal was corrected by deploying both strakes at 20° initially, then differentially from 20° to create a yawing moment. The off-surface flow visualization showed that in the case of the small single strake deflection, the resulting forebody/strake vortex remained close to the surface and caused accelerated flow and increased suction pressures on the deflected side. When both strakes were deflected differentially, two forebody/strake vortices were present. . |
| 157 | I. Roehle, C. Willert, R. Schodl | APPLICATIONS OF THREE DIMENSIONAL DOPPLER GLOBAL VELOCIMETRY IN TURBO-MACHINERY | Doppler global velocimetry, DGV, internal flows | A Doppler global velocimetry (DGV) system optimised for time-averaged three component velocity measurements has been applied in two situations. The system uses a single viewing direction in conjunction with three different illumination directions. |
| 158 | Alain Pelletier, Robert C. Nelson | THE USE OF OFF-SURFACE FLOW VISUALIZATION IN A DYNAMIC BEHAVIOR STUDY | vortex breakdown, vortex lift-off, roll moment coefficient, critical state and delta wing | An experimental investigation was conducted to study the dynamic behavior of an double-delta wing in roll. Different rolling behavior was observed as a function of the model sting angle. These dynamic regimes were found to be related to the behavior of the leading-edge vortices present over the wing. The presence of vortex breakdown and vortex lift-off affected the type of behavior obtained when the wing was free to rotate about its longitudinal axis. |
| 159 | M. Ismailov, T. Ishima, T. Obokata, M. Tsukagoshi and K. Kobayashi | VISUALIZATION AND PDA-MEASUREMENTS IN HIGH PRESSURE SPRAY FLOW | spray, high-speed video, laser sheet, phase-Doppler anemometer | Spray flow is induced by high-pressure swirl injector at different injection durations of 0.25 up to 4.0 ms under the pressures of 5 and 7 MPa. The flow has been qualitatively and quantitatively investigated using high-speed video camera (HSVC) at the speed of 40500 frames/s and phase-Doppler anemometer (PDA). |
| 160 | Felix Weinberg | RECENT STUDIES OF LIGHT REFRACTION BY FLAMES | refraction, flames, beam deflection, microgravity | Recent advances in research into refraction by flames are reviewed. It is shown that deflection profiles and hence Schlieren marking for axially symmetrical premixed flames do not tend toward the planar flame solution as the radius tends to infinity and that the deviation differs for concave and convex geometries. The effects of refraction on the use of light sheet methods in combustion are elucidated. The optics of small diffusion flames in the absence of convection is analysed with reference to the disappearance of shadows in electrically simulated microgravity. |
| 161 | S. Matsumura K. Takayama O. Onodera | HOLOGRAPHIC INTERFEROMETRIC VISUALIZATON OF VERY WEAK SHOCK WAVES APPEARING IN AUTOMOBILE EXHAUST PIPES | weak shock wave, automobile exhaust system, hologaraphic interferometry, aerodynamic noise | When an automobile engine is started and quickly accelerated, unpleasant noises are known to be created, whose tones are similar to that generated when a thin plate vibrates. In our previous works, it was revealed by means of holographic interferometricvisualization that the noises were actually created by shock waves into which compression waves released from the engine cylinder into the exhaust pipe coalesced while their propagation. To design engine silencers and mufflers, basic research program in which a shock tube was in-tensively used for the propagation of very weak shock waves in these passages to be simulated, has been suc-cessfully carried. For the development of effective en-gine silencers a holographic interferometric flow visu-alization was conducted in a shock tube to observe a very weak shock wave and its associated flows. |
| 162 | Yousef Haik Ching-Jen Chen | VISUALIZATION OF MAGNETIC CELL SEPARATION | red blood cells, magnetic separation, susceptibility, microscopic, visualization, cancer | In this study the separation of red blood cells from the whole blood using a magnetic technique is discussed and visualized. The separation of red blood cells from the whole blood is an important procedure in photopheretic treatment of white blood cells of patients with skin cancer. The microscopic visualization of the separation process is presented. It is found that the magnetic technique of blood cell separation can be achieved in a continuous fashion contrary to existing centrifugal techniques. A safe coupling of the red blood cell to a magnetic microsphere enhances the magnetic susceptibility of red cells. The separation is achieved when the coupled cells and microspheres are retained by a magnetic field and the plasma solution with white cells is allowed to flow to a different chamber. The red cells are then decoupled from the magnetic microspheres and allowed to flow to combine the treated white cells before injection to the patient. |
| 163 | D. Ambrosini, A. Ponticiello, D. Paoletti, G. Galli | INVESTIGATION OF NATURAL CONVECTION AROUND CYLINDERS BY ELECTRO-OPTIC HOLOGRAPHY | natural convection, cylinders, electro-optic holography | In this work electro-optic holography is proposed as a tool in flow visualization As an example, onset of natural convection above circular cylinderin air is investigated. |
| 164 | N Toy, S McCusker & E Savory | THE USE OF IMAGE PROCESSING FOR STUDYING LARGE-SCALE TURBULENT MOTION | novel technique, structure tracking, digital image processing, jet in crossflow | The work presented here concerns the development of a digital imaging approach to the quantification of turbulent flow characteristics. A method for creating a laser sheet using a diode laser and basic electronic sampling equipment is outlined and this technique is applied to the flow regime in the shear layer of a jet in a crossflow. The results obtained using this technique indicate that the large-scale structures within the shear layer of a jet in a crossflow are of a size between the integral length scale and the shear layer width. Furthermore, the characteristic turbulence intensity of these structures is comparable to that of the turbulence intensity of the mean flow, when the turbulent intermittency is taken into consideration. It is also shown that the convection velocity of the large-scale shear layer structures and the characteristic turbulence intensity of these structures, measured by the fluctuation in the convective velocity, is generally independent of structure size. |
| 165 | Suxun Li and Yongkang Chen | A COMPARISON OF SEPARATED FLOW PATTERNS INDUCED BY RECTANGULAR AND CIRCULAR CYLINDERS | separated flow, circular cylinders, rectangular cylinders | The shock wave / boundary layer interactions induced by the obstacles, which mounted on the surface, are very popular in supersonic and hypersonic flows. One kind of the typical projects for the interactive flowfield induced by blunt fins or cylinders on the surface has been studied for a long time. It shows the complex flows including separated flows and reattached flows around the cylinders [4-9]. The influences of the geometry and length scales of the cylinders on the separated flow features were described under various upstream conditions according to each certain purpose. In this work, a comparison of two kinds of the interactive flowfields generated by rectangular and circular cylinders is presented based on the experimental results in hypersonic flow. The schlieren photographs and the oil flow patterns gave the visualizations. The shock wave shapes, strength and scales of the separated regions for both models were shown by schlieren photos, and the skin friction lines on the surface were obtained. |
| 166 | E.I. Palchikov, S.V. Sukhinin, A.S. Besov, D.G. Akhmetov, D.A. Kondratenko. | X-RAY METHOD FOR FLOW VISUALIZATION OF HETEROGENEOUS FLUID IN POROUS MEDIA | heterogeneous liquids, flows, pulse radiography visualization, porous media, oil-bearing rocks x-raying, acoustics, filtration, saturation, own frequencies | The purpose of the present work is visualization and control of filtration for two-component (heterogeneous) liquids in porous media in normal conditions and high pressure, high temperature conditions. The possibility of developing a simple radiographic procedure for observing the shape and position of liquid boundaries inside a low-porosity compact medium (oil-bearing sandstone) at the impregnation stage was investigated. In a non-transparent thick-wall container modeling the conditions of oil reservoir on the depth 1.5-2 km by means of X-raying the control of liquid consumption, appearing and settling the suspension and state of moistening surfaces was carried out. |
| 167 | G.M.Zharkova, A.V.Dovgal, V.N.Kovrizhina, B.Yu.Zanin | FLOW VISUALIZATION ON A LOW ASPECT RATIO WING BY LIQUID-CRYSTAL COATINGS | optical diagnostics, liquid crystals thermography, liquid film,wing | Application of liquid crystal thermosensitive coatings to flow visualization at low subsonic velocities is considered. A particular aerodynamic problem focused by the study is the flow on a finite-span wing placed at high angles of attack. The developed visualization technique includes registration and following digital processing of the liquid crystal data. By the method the temperature distributions on the test surface are reconstructed which provide time- averaged surface flow patterns. |
| 168 | Xing, H. J. and Wu, Y. | VISUALIZATION OF FIRE PLUMES USING SCHLIEREN TECHNIQUES | fire plumes, Schlieren techniques and flow visualization | A modified positive-negative schlieren system has been set up in this study to visualize the flow interaction between fire plumes and surrounding surfaces. Three configurations, which concern fire spread in buildings, were set up. They include a fire against a vertical wall, fire impinging flat ceiling and a fire spread on an inclined surface. Sequences of schlieren images were taken for each case to investigate the behaviour of buoyant plumes. Results showed that the improved schlieren system is a powerful tool to study the invisible hot flow pattern in fire plumes. Analysis of schlieren images was carried out to reveal the features of fire plumes in each configuration. Further treatment of the schlieren images was also discussed. |
| 169 | S. Rainieri, G. Pagliarini | PERFORMANCE ANALYSIS OF A FPA IR CAMERA FOR SURFACE HEAT FLUX RESTORATION | heat flux restoration, thermal imaging | The present paper is focused on the heat flux restoration in a two--dimensional problem, that is it deals with the heat flux estimation given the measured surface temperature distribution. The straightforward differentiation of the temperature function does not lead to accurate results, since the problem is extremely sensitive to measurement errors. It is regarded, in fact as an ill-posed inverse problem. The method employed in the present investigation to recover the heat flux distribution is based on an iterative scheme formulated with the aid of a numerical procedure. The basic requirement in order to restore the heat flux is a high definition and high quality temperature measurement. This can be easily achieved by means of a thermographic system, and in particular with a new technology Focal Plane Array Infrared (FPA IR) camera. The performance of this type of camera has been evaluated by studying a typical heat transfer test problem. |
| 170 | N.NishikawaT.Ishide S.Kaminaka and F.Mikami | VISUALIZATION AND MEASUREMENT OF FLOWS WITH LARGE VORTICAL PATTERNS | separated vortical flow, body of rotation, channel flow | Two types of vortical flow are investigated. First is the separated flow at leeside of a parabolic body of revolution in a wind tunnel. Second is the flow in a rectangular water channel with polymer additive for drag reduction. In the wind tunnel the flow ata<40deg is studied by visuali-sation and measurement ,especially by a curved-light-sheet. The longitudinal vortex structure formed behind the body and unsteady flow chara-cteristics are investigated. Reynolds number is 1.55×104 referred to base diameter:75mm of the body which has a circular-cylinder aft-body. In this air flow case the main quantitative data are obtained by C.T.A. anemometry, however the application of Path-line method ,Two-time level PTV are also discussed for the high relative velocity of tracer image across a frame of the V.C.R. As a PTV application we describe another vortical flow pattern inside the water flow in a channel of rectangular cross section. |
| 171 | Ch. Bruecker | A TIME-RECORDING DPIV-STUDY OF THE SWIRL SWITCHING EFFECT IN A 90° BEND FLOW | 90° bend, dpiv, swirling flow, secondary vortices | The unsteady nature of secondary vortices generated in a 90° curved bend was studied with DPIV. The chronological measurement of the secondary flow field in a cross-sections of the channel downstream of the bend let recognize a low-frequency increase of the strength of the streamwise vortices in an alternating manner. The rough plane of symmetry of the flow oscillates with the same frequency about the geometrical plane of symmetry. |
| 172 | Kazuyoshi Nakabe, Yu Yamamoto, Elzbieta Fornalik, Wei Chen, Kenjiro Suzuki | VISUALIZATIONS OF OBLIQUELY DISCHARGED JET FLOWS AND THEIR HEAT TRANSFER ENHANCEMENT REGIONS | jet impingement, crossflow, longitudinal vortex, heat transfer, liquid crystal, ldv, visualization | Flow visualizations and heat transfer measurements were carried out for obliquely discharged jets into a crossflow. The oblique jet issues through a circular nozzle with an oval shape open end, which was mounted flush with a top wall surface of a test section, and impinges onto the target heat transfer surface of a top wall. The jet is characterized by a pitch angle measured up from the nozzle-installed wall and a skew angle measured relative to the crossflow stream. One more inclined jet with the same pitch angle and the opposite skew angle was situated downstream at a distance of 10 nozzle diameters apart from the upstream jet. Not only flow and heat transfer characteristics of the single jet but also the interaction between the two jets were investigated using the following visualization techniques; plane laser light illumination of cross-sectional jet flow fields with the addition of fluorescent dyes, and color-to-temperature conversion of thermo-chromatic liquid crystal sheets pasted on the target. |
| 173 | Susumu Kobayashi, Takashi Adachi, Tateyuki Suzuki | NON-SELFSIMILAR BEHAVIOUR OF THE VON NEUMANN REFLECTION: AN APPROACH WITH A METHOD OF MULTIPLE STEPS | von Neumann reflection, non-selfsimilarity, unsteadiness, von Neumann paradox | The purpose of the present paper is to consider the von Neumann reflection (vNR) which takes place for a small incident shock Mach number and a small wedge angle. A series of experiments has been performed with an ordinary smooth straight wedge and a step-like wedge which simulates the former. Reflection configurations over the latter have been helpful in getting any physical insight to the phenomenon (method of multiple steps) according to the authors’ previous works. In the shock reflection experiment over the step-like wedge, a compression wavelet issues at each step and each wavelet has a corresponding pseudo-triple point. By measuring the segment length of the neighbouring pseudo-triple points, it has been shown that the wavelets issued later tend to overtake the precursory one as the incident shock proceeds. This result has suggested unsteady nature of the vNR. Contrary to the established notion of shock reflection phenomena over straight wedges, while the triple point trajectory was approximate. |
| 174 | Shigeki Imao, Motoyuki Itoh, Yasuaki Kozato, Kazuaki Iwatsuki | TAYLOR VORTEX FLOW OF DILUTE POLYMER SOLUTIONS | transition, Taylor vortex, flow visualization, dilute polymer solution, ldv | The effects of small additions of the polymer to the water on the flow between rotating concentric cylinders have been studied experimentally by means of flow visualization and LDV measurement. The experiments have been carried out with the inner cylinder rotating and the outer one at rest. As the polymer is added to the water, the flow is destabilized and Taylor vortex appears at lower Taylor number than that for water. Though the addition of the polymer has little effect on the azimuthal wavenumber and on the speed of travelling azimuthal waves, the axial wavelength of the Taylor vortex increases markedly depending both on the polymer concentration and on the radius ratio. When Taylor vortices are built up, secondary flow is weakened with an increase in polymer concentration. In the turbulent Taylor vortex flow of the polymer solution, the velocity gradient at the wall becomes small and there is a region with an inverse velocity gradient. |
| 175 | Katsumasa Suzuki, Kennichirou Asahara | BLOCK DIAGRAM REPRESENTATION OF PIPELINE DYNAMICS | pipeline, hydraulics, transient, simulation, block diagram, gui | The calculation process for a pipeline system which, to date, has been performed using a computer program, is displayed in the form of a block diagram. As a result, the dynamics of the pipeline can now be calculated using simulation software with a graphical user interface. Visual understanding of the calculation process is also facilitated. |
| 176 | Shigeru Murata, Masayoshi Kawamura, Yoshihiro Nakagawa | A DEPTH-FROM-DEFOCUS FOR PARTICLE IMAGES AND ITS APPLICATION | depth measurement, defocus, tracer particles, wave height measurement | This paper describes a depth-from-defocus for detecting the depth of small particles distributed in three-dimensional space and its application to wave height measurement. In this method, we use a pair of particle images that are simultaneously captured using a 3CCD camera with two different focus settings on red and green frames, and the particle depth is uniquely determined using the blur parameters evaluated for each particle recorded on the two frames. The present method is successfully applied to wave height measurement to show its reliability and usefulness in flow measurement. |
| 177 | Shigeru Murata, Matsumi Masuda | DIGITAL DETECTION OF PARTICLE DEPTH FROM OVERLAPPING INTERFERENCE FRINGES | depth measurement, in-line holography, digital reconstruction, tracer particle | In this paper, a technique of depth measurement has been developed for the detection of the depth of small particles distributed in three-dimensional space. The technique is based on in-line holography and the image reconstruction from observed in-line hologram pattern is virtually performed on the Fresnel diffraction formula to know the position of a corresponding real image. The measurement accuracy of the present method is examined for the hologram pattern with overlapping interference fringes. Performance tests are numerically and experimentally carried out to check the applicability of the present method to flow measurement. |
| 178 | M. Maeda, A. Fujiwara, A. Tokuhiro, K. Hishida | INVESTIGATION OF MOTION OF A RELATEVELY LARGE BUBBLE AND THE PIV VISUALIZATION OF SURROUNDING FLOW BY LIF TRACER PARTICLES | lif tracer particles, piv, bubble | With a bubble in the flow field a particular difficulty is the precise observation of the field near the bubble because the bubble surface acts as a strong source of reflection of the incident light. The scattering light from small tracer particles then can not be observed especially in the vicinity of the bubble surface. The particles that emit a different wavelength from the incident light lead us to apply a fluorescence technique instead by the scattering of incident light. With this contrary the bubble boundary could hardly be recognized, as the incident light was equally filtered out from the investigated region. The periphery of the bubble was conveniently captured by its shadow illuminated with an infrared LED array arranged on the opposite side. The small spherical polymer particles that serve as a laser-induced fluorescence material and whose density was close to that of water, was employed as tracer. |
| 179 | A. Eder, B. Edlinger, M. Jordan, F. Mayinger | INVESTIGATION OF THE TRANSIENT FLAME DEVELOPMENT USING A COMBINATION OF ADVANCED OPTICAL MEASUREMENT TECHNIQUES | premixed combustion, laser-doppler-velocimetry, length-scales, schlieren-cinematography, laser-induced predissociation-fluorescence | The present paper deals with the investigation of various combustion processes by means of highly sophisticated optical measurement methods. Many optical techniques are capable of describing phenomena in thermo-fluid-dynamics, but only a limited number of process variables are obtained by each of these techniques. In order to develop and to validate computer codes simulating combustion phenomena, only the combination of several measurement techniques on comparable experiments leads to a satisfactory data base containing the most important process variables. The application of the high-speed Schlieren-technique, the Laser-Induced Predissociation Fluorescence, and the Laser-Doppler-Velocimetry on comparable transient combustion processes in several test-facilities is shown within this paper. Emphasis is put on the determination of length-scales due to their importance regarding turbulent combustion. |
| 180 | J.R. Kadambi, S. Amirthaganesh, H. Mu, W.T. Martin, D.S. Jang, M.P. Wernet | MEASUREMENT OF PARTICLE SIZE AND VELOCITY IN TWO PHASE FLOWS USING PIV | PIV, defocus, sizing, intensity weighting, particle laden jet | A particle imaging velocimetry (PIV) system for measuring the particle size in two phase flows is described. The PIV system is calibrated by capturing images of stationary particles. The effects of the Gaussian distributed intensity variation across the depth of the light sheet and the optical collection system’s depth of field are investigated. These effects provide insight into designing a balanced illumination and collection optical system necessary to obtain constant particle size estimates independent of their position within the light sheet. Accuracy in the particle size estimates on the order of 9% are obtained. It is also shown that size distributions in a mixture of polydisperse particles can be obtained with a maximum deviation of 10-20% from the actual size distribution. The PIV system is successfully tried in a two phase particle laden jet-concurrent gas flow and the sizes and velocity of the particles are obtained in a square duct. |
| 181 | C.P. van Dam, H.J. Shiu, D.W. Banks | REMOTE IN-FLIGHT BOUNDARY LAYER TRANSITION VISUALIZATION USING INFRARED THERMOGRAPHY | infrared thermography, boundary layer transition, in-flight measurements | The feasibility of remote infrared thermography of aircraft surfaces during flight to visualize the extent of laminar flow on a subject aircraft was examined. In general, it was determined that such thermograms can be taken successfully using an existing airplane/thermography system (NASA Dryden’s F-18 with infrared imaging pod) and that the transition pattern and, thus, the extent of laminar flow can be extracted from these thermograms. Depending on the in-flight distance between the F-18 and the subject aircraft, the thermograms can have a spatial resolution of as little as 0.1 inches. The field of view provided by the present remote system is superior to prior stationary infrared thermography systems mounted in the fuselage or vertical tail of a subject aircraft. An additional advantage of the present experimental technique is that the subject aircraft requires no or minimal modifications. |
| 182 | In-seop Lee, Akikazu Kaga, Katsuhito,Yamaguchi,Kwang-ha Suh | FLOW VISUALIZATION TECHNIQUES APPLIED TO THE ANALYSIS OF RECIPROCATING COMPRESSOR SUCTION SYSTEM | piv, reciprocating compressor, direct suction ratio, visualization | The applicable compressor designs are those in which the suction gas from the evaporator is dumped into the compressor shell, and is then drawn through a muffler into the compressor. To study the flow pattern of the suction gas in transit between the suction pipe outlet and the suction muffler inlet, we have proposed a technique of concentration measurement through digital image processing. The experiment of mass transfer in a suction gas flow has implied the measurement of distribution of tracer concentration change with time. In this paper, the direct suction ratio( DSR ) is defined as the ratio of the flow rate of refrigerant directly sucked to the total flow rate from the suction pipe, and measured with a new technique using digital image processing. Although refrigerant flow velocity around suction pipe and muffler is required as a fundamental data for further improvement of the performance, there has been no report or paper which measures these data due to the difficulty in insertion of velocity sensor. |
| 183 | In-seop Lee , Akikazu Kaga, Katsuhito Yamaguchi, Oh-sung kwon, Hong-yul Yoon | PERFORMANCE EVALUATION OF PIV ALGORITHM “GRAY LEVEL DIFFERENCE ACCUMULATION” USING PIV STANDARD IMAGES | piv, standard image, pattern tracking algorithm, performance evaluation | Particle imaging velocimetry ( PIV ) is a technique which allows the velocity of a fluid to be simultaneously measured throughout a region illuminated by a two-dimensional light sheet. A lot of PIV techniques and PIV systems have been developed. We have been proposed a pattern tracking technique using gray level difference accumulation as the similarity index of image fragments. The development of standard images and its usefulness were presented and discussed, in order to increase the objectivity and the use of PIV , in PIV ’97 Fukui Workshop. In this paper, we investigate the effects of the characteristics of visualized images on the performance of our pattern tracking algorithm by applying it to standard images, and propose an idea to improve its performance to flow images which have high out-of-plane velocities. |
| 184 | Jan Dahlsveen, Lars R. Saetran | FRAGMENTATION OF LIQUID DROPLETS IN WATER - LASER SHEET VISUALIZATION | fragmentation, liquid droplet, pulsed laser | A pulsed laser system is used to study mechanically induced shock-wave fragmentation of isopentane droplets in water. The fragmentation process is visualised by a digital full-frame CCD-camera. Two subsequent frames are grabbed when the shock wave passes the rising liquid droplet, and the fragment sizes and critical Weber-number for the liquid-liquid system are found. The relative velocity behind the shock front is measured by Laser-Doppler-Velocimetry, and shock wave pressures are measured by two piezo-electric pressure-transducers. The experiment showed that the measured relative velocity behind the shock-front is in good agreement with the theory based on shock wave propagation. The Weber-number for the liquid-liquid system must be high to enable fragmentation of isopentane droplets. |
| 185 | C. Freek, W. Hentschel, W. Merzkirch | HIGH SPEED PIV – A DIAGNOSTIC TOOL FOR IC-ENGINES | flow visualization, high speed film, IC-engine, particle image velocimetry | To investigate the temporal flow structure in the combustion chamber of IC-engines, time resolved Particle Image Velocimetry (PIV) measurements were applied to a motored engine at 1000 rpm. A 16mm high speed film camera was used together with a copper vapour laser for illumination of the light sheet to record images with up to 8kHz. The images were subsequently digitised for digital evaluation. A cross-correlation algorithm with intermediate image shift correction was used to evaluate the 2-dimensional instantaneous vector fields. The described experimental set-up is capable to record a 2-dimensional flow field development. Results are shown for the in-cylinder flow field development in a fully resolved intake and compression stroke. As well, comparisons between successive cycles are carried out to demonstrate the cycle-to-cycle variations late in the compression stroke inside an IC-engine. |
| 186 | Jerry M. Chen, Ho-Cheng Chueh | VISUALIZATION OF FLOW AROUND A RECTANGULAR PLATE DISTURBED BY ONCOMING PERIODIC VORTICES | separation bubble, periodic disturbance, vortex shedding, secondary vortex | The flow past a rectangular plate subjected to a periodic disturbance has been studied experimentally at a Reynolds number of 1700 based on the plate thickness. The experiments were performed in a wind tunnel using flow visualization together with surface pressure measurements for the plate models having chord-to-thickness ratios in the range 3-10. The periodic disturbance in form of a vortex street was generated by placing a symmetrical airfoil at a certain distance upstream of the test plate. For the head-on impingement of the vortex street with the plate, the oncoming vortices appeared to reorganize the vortical structure in the separation bubble with the formation of a secondary vortex, causing a discernible low frequency flapping motion of the bubble. The shedding of secondary vortex resulted in a sharp rise in mean pressure distribution immediately downstream of the leading edge. |
| 187 | Blasiak Wlodzimierz, Baranski Jacek, Olsson Hilmer, Vaclavinek Jiri | PHYSICAL MODELLING OF FLOW AND COMBUSTION IN INDUSTRIAL EQUIPMENT | combustion, flow pattern, modelling, visualization, neutralisation | Physical modelling is a convenient way to simulate combustion and flow patterns by visualization in cold, isothermal models. These models must be used with certain similarity criterions to visualise real industrial processes properly. Together with mathematical modelling high accuracy in simulation will be achieved. This paper presents applications of physical modelling to study large-scale combustors in two and three dimensions. This is done in steps when beginning with a burner model to investigate the flame and continuing with a boiler model to visualise the flow pattern and combustion processes. Physical modelling in industrial processes is used to achieve retrofit techniques to reduce emissions and to get a more rapid and efficient mixing of reactants. |
| 188 | S. Doan-kim, F. Plourde, D. Couton, M. Prevost, F X. d’Herbigny | IMAGE PROCESSING FOR VORTEX-SHEDDING VISUALIZATION AND CHARACTERISATION | visualization, vortex-shedding, acoustic, shear-layer | This paper deals with the simulation of a solid propellant rocket motor in cold gas, in order to study the possible link between the vortex-shedding phenomenon and the internal geometry. Flow visualization technique has been developed and tested to characterise the shear-layer and vortices creation between the obstacle and the submerged nozzle. This approach makes it possible to estimate quantitatively the unsteady behaviour of the internal flow. Results show the generation of longitudinal vortex structures on a frequency close to the first acoustic mode, with a high Reynolds number R=72000 and a mean flow Mach number M=0.068. |
| 189 | Masaki Fuchiwaki, Kazuhiro Tanaka, Takeshi Nakada | DISCRETE VORTEX VISUALIZATION ON THE INTEGRATED STREAKLINE OF SEPARATION OF A PITCHING AIRFOIL | unsteady flow, separation, flow visualization, shear flow, vortex, Schlieren method, pitching airfoil | Dynamic behaviors of vortices in a shear layer generated behind the leading edge of pitching airfoils have been visualized with a wind tunnel, the schlieren visualization technique and a high speed VTR. The Reynolds number based on the chord length is Re=4,000, the pitching amplitude is 30 deg. around 60 and 30 deg. mean angle of attack and around the half chord axis. The non-dimensional pitching rate k =c / 2 U0 is less than k=0.25. The number of VTR frames are 1000 a second. |
| 190 | F. De Gregorio , J. Kompenhans , C. Willert, B. Bretthauer, M. Raffel | INVESTIGATION OF UNSTEADY FLOW FIELDS ON HIGH SPEED PROPELLERS BY MEANS OF THE PARTICLE IMAGE VELOCIMETRY TECHNIQUE | particle image velocimetry, tip vortex, propellers, wind tunnel, flow velocity fields | This paper illustrates the measurement campaign performed at the Low Speed Tunnel (LST) of the DNW in order to demonstrate the applicability of the Particle Image Velocimetry (PIV) to large industrial facilities. The flow field measurements have been carried out on the model of a modern high speed propeller. The unsteady flow field downstream of the propeller disk has been investigated and the instantaneous and the mean flow velocity fields have been measured for different angle of attack, jaw angle and rotational speed of the propeller. Furthermore, the trajectories and the intensity of the tip vortex have been evaluated. The main objective is to illustrate that by means of PIV it is possible to obtain accurate quantitative measurements of unsteady flow fields using the same technologies (tracer particles, laser light sheet, video cameras) as the classical qualitative flow visualization. |
| 191 | Yasuhiko Sugii, Taketoshi Okuno, Shigeru Nishio | PHYSICS-BASED IMAGE MEASUREMENT OF FLOW FIELD | image measurement, physics-based measurement, fluid dynamics, constraint of image | PIV technique is examined from the viewpoint of the problem of identification for flow. The process of obtaining the velocity distribution from images can be generalised as a parameterisation problem of dynamical system. In most conventional techniques, the parameters have been estimated using a liner model. A new PIV technique based on physics is proposed. The velocity distribution is obtained by new correlation technique using estimated and observed images. The present method is applied to the PIV standard images prepared by numerical simulation. |
| 192 | Fathi Finaish and Keith Gray | AN ASSISTED COMPUTER APPROACH TO DOCUMENT AND ANIMATE PHYSICAL VISUALIZATIONS OF UNSTEADY FLOWS | computer assisted, unsteady flow documentation, animation | Physical visualizations of unsteady flows play an imperative role in guiding and economizing computational fluid dynamics (CFD) efforts and provide an excellent educational tool. However, despite the availability of these visualizations in open literature, they have not been utilized effectively either in research or in education. Perhaps this is due to the limits of the media in which this data is published. Due to space limitations, documentation of large photographic sequences with adequate time resolutions is extremely restrained in journal papers and conference proceedings. Furthermore, it is difficult to relate static images to the dynamics of the flow developments in a given flow configuration. In unsteady flows, a single picture is unable to describe the occurrences in the flow over its full range of development. Thus, publishing this data using a media that is more accessible, animated, and displayable than the traditional publishing forms is in order. |
| 193 | J.M. Desse C. Fatien | STUDY OF UNSTEADY WAKE FLOW PAST A CYLINDER BY THREE COLOR DIFFERENTIAL INTERFEROMETRY | unsteady wake flow, differential interferometry, cylinder | It is shown that differential interferometry using a Wollaston prism and a three coloured laser source is an optical technique that has all the advantages of differential interferometry in polarized white light and of the classical monochromatic interferometry. The interference fringe pattern obtained is very large, coloured and presents a central white fringe which enables the easy identification of the zero order of the interferogram. The three coloured source is obtained by filtering the unwanted lines of the ionized laser (mixed Argon and Krypton) and balancing the three red, green and blue lines by a technique which involves placing birefringent plates between the polarizer and the analyser, the thickness of which has been calculated to create a natural filter. The unsteady aerodynamic flow downstream of a circular cylinder has been visualized by this technique, which shows that the power of the light source is sufficient to record the interferograms at a high rate. |
| 194 | H.-J. Müller, H. Krehl | INVESTIGATION OF DISPERSION PROCESSES USING WIND TUNNEL MODELLING AND LASER-LIGHT-SHEET TECHNIQUE | livestock building, ventilation, emission, air flow, wind tunnel | The keeping of animals in livestock buildings requires ventilation. The ventilation of such buildings lead to emissions and immissions The dispersion of emitted substances (i. e. odours) in the atmospheric boundary layer around live-stocks is influenced by factors like the specific wind profile (velocity and turbulence), the terrain structure, the shape of the building, the arrange-ment and design of the air drains and from the speed of the air through inlets and outlets Mini-mum distances between residential areas and livestock buildings have been specified in Ger-many depending on the emitted flow of odours and the distribution conditions in the specific site. Besides the real site investigations dispersion processes are systematically investigated by using wind tunnel modelling. |
| 195 | E. Rouland, A. Floch, A. Ahmed, D. Dionnet, M. Trinité | CHARACTERISATION OF INTAKE GENERATED TUMBLE FLOW IN 4-VALVE ENGINE USING CROSS-CORRELATION PARTICLE IMAGE VELOCIMETRY | particle image velocimetry, combustion engine, tumble ratio | The tumble flow patterns, during the intake and compression strokes, were investigated, in a four-valve, four-stroke transparent single cylinder research engine. The single cylinder engine had a transparent quartz liner and a quartz-top extended piston. Two-dimensional in-cylinder velocity distributions were measured with cross-correlation Particle Image Velocimetry (PIV) on planes parallel and perpendicular to the piston. The velocity fields were obtained at several crank angles. PIV investigation in the various planes allowed the tumble flow pattern to be deduced, from the two-dimensional ensemble-averaged flow patterns. Tumble motion was found to be a 2D-roll motion in which the rotation axis deformed on the two extremities towards the piston head. Different flow characterisation parameters were derived and used for the post-processing of the PIV measurements. Parametric studies were performed to analyse the influence of the tumble intensity, engine speed and volumetric efficiency on the tumble flow. |
| 196 | Janusz Jankowski, Janusz Plutecki | MEASUREMENT OF MOMENTARY VELOCITY FIELDS IN LIQUID FLOW WITH HYDROGEN BUBBLE METHOD | hydrogen bubble method, flow visualization, computer-aided measurement, image analysis, measurement of velocity in liquid flow, flow field visualization, particle image velocimetry. | The hydrogen bubble method is a technique which permits to make a map of velocity distribution in given cross-sections and fix the initial localization of the visualized particles at the start of recorded movement.A development of this method is the technique elaborated at the Institute of Machine Construction and Operating, Technical University, Wroclaw, Poland by Dr. L. Bobowski under direction of Prof. J. Plutecki [2]. It was used to study phenomena at the rotor inlet (prerotation, back currents) during its operation in the initial range of flow characteristics. The technique permitted for sufficiently precise determination of distribution of momentary velocities along linear cross-section, i. e., for obtaining a quantitative pattern of the flow field at the level of momentary velocities. However, it does not eliminate completely difficulties connected with determination of these velocities at a planar cross-section. |
| 197 | K. Affeld, L. Goubergrits, U. Kertzscher, H. Oswald, E. Wellnhofer | X-RAY BASED MEASUREMENTS OF FLUID VELOCITY IN A HIGH BUBBLE DENSITY FLOW | flow visualization, bubble flow, X-ray, three dimensional flow field | This article presents a new method to meas-ure the fluid velocity in bubble flows. Bubble flows occur in bubble columns, as they are widely applied in biotechnology. Despite its wide appli-cation, the bubble flow is not really well under-stood, because it has so far resisted detailed ex-perimental investigation. The otherwise very suc-cessful methods of flow measurements such as Particle Image Velocimetry (PIV), Laser Induced Fluorescence (LID) and Laser Doppler Veloci-metry (LDV), fail, because they are based on the straight passage of light. A bubble represents a phase boundary, which reflects light. Hence light cannot penetrate deeply into a bubble flow. This hindrance is overcome with the method presented here: X-rays are used instead of light. Theses rays penetrate the bubble flow in straight lines, they are not influenced by the different refraction indices of gas and liquid. The flow is marked by X-ray absorbing particles, which in addition are buoyant. |
| 198 | Illari Vihinen, James R. Gord, Jeffrey M. Donbar, Gregory J. Fiechtner, Campbell D. Carter, and J. C. Rolon | VISUALIZATION OF VORTEX-FLAME INTERACTIONS IN A COUNTERFLOW DIFFUSION FLAME | extinction, laminar flames, vortex, digital piv, turbulence | The dynamic interaction between a laminar flame and a vortex is examined. The hydroxyl (OH) layer produced by the flame is imaged using planar laser-induced fluorescence (PLIF), and preliminary vortex-characterisation data are acquired using acetone PLIF and digital, two-colour particle-image velocimetry (PIV). The hydrogen-air flame is supported in a nonpremixed opposed-jet burner. The apparatus is found to produce highly repeatable events, making it ideal for studying the interaction between a flame and an isolated vortex. A distinct annular extinction of the OH layer is observed, in good agreement with previous computational modelling predictions of the apparatus. In cases with no extinction of the OH layer, enhanced burning is observed during the vortex-flame interaction. |
| 199 | Martin Wetzel, Cila Herman | MEASUREMENT OF TRANSIENT TEMPERATURE FIELDS BY HOLOGRAPHIC INTERFEROMETRY IN THE PRESENCE OF PRESSURE VARIATIONS | holographic interferometry, high-speed unsteady temperature fields, thermoacoustics | In conventional applications of holographic interferometry in heat and mass transfer the field parameters of interest are usually density, temperature or concentration. In this paper a new field parameter, pressure, was introduced into the evaluation procedure of interferometric fringe patterns. Based on newly derived evaluation formulae, the limitations of the conventional approach measuring temperature in the presence of pressure variations are discussed together with methods to overcome these limitations. A comparison of experimental data with theory shows good agreement, which verifies the evaluation formulae. |
| 200 | Jonathan W. Naughton, James L. Brown | SKIN FRICTION MEASUREMENTS IN COMPLEX FLOWS USING TWO-IMAGE THIN-OIL-FILM INTERFEROMETRY | skin friction, viscous drag, interferometers, optical measuring instruments, turbulent boundary layer, three dimensional boundary layer, thin films | An instrument capable of making skin-friction measurements on surfaces beneath complex three-dimensional flows is described. This instrument builds upon the success of earlier techniques that measured the height of a thin-oil film using interferometry. The Surface-Imaging Skin Friction (SISF) measurement technique was developed to obtain maximum measurement accuracy in complex flows, and, as a result, the theory used for its development has a rigorous basis. Two technical innovations set this technique apart from others. The first is that the technique is capable of determining the phase of an interferogram (and thus the height of the oil) at all locations where suitable fringes exist. The second is that surface shear stress is determined by solving the thin-oil-film equation using the height distributions from two interferograms. |
| 201 | Hiroshi Higuchi, Jinzhong Zhang and Hélène Balligand | PARTICLE IMAGE AND DYE FLOW VISUALIZATION BEHIND SOLID AND SLOTTED DISKS IN UNSTEADY MOTIONS | flow visualization, piv | Wake development behind near-impulsively started solid and slotted disks was investigated and compared with that behind a two-dimensional flat plate. To complement a dye flow visualization study, a Particle Image Velocimetry (PIV) software utilizing the multi-layer adaptive algorithm was applied to the present flow configurations. The time evolution of the vorticity field was obtained as well as the circulation and impulse in the wake. |
| 202 | Oronzio Manca , Biagio Morrone, Sergio Nardini | THE EFFECTS OF LONGITUDINAL ASPECT RATIO ON NATURAL CONVECTION IN INCLINED CHANNELS | natural convection, inclined parallel plate, flow instability, flow visualization, laser sheet imaging method | In this paper a visualization study on the flow structures in air natural convection between inclined parallel plates was carried out. The lower plate was at uniform heat flux and the upper plate was unheated. The visualization was obtained by means of a laser light sheet and incense smoke. The pictures were taken by a still camera. The effects of the longitudinal aspect ratio and inclination angle were investigated. The three investigated angles were 75°, 85° and 90°; the channel gaps were equal to 20.0, 32.3 and 40.0 mm and the corresponding Grashof number varied between 3.1·104 and 1.1·106 The pictures of the longitudinal section showed that the flow separated from the lower plate and there was an inflow at the exit edge. As result of thermofluidynamic instability, secondary motions were observed in the cross-stream sections. |
| 203 | A.Cenedese, G.De Angelis | NEAR FIELD ANALYSIS OF A JET IN CROSS-FLOW BY MEANS OF LIF AND PTV | lif, piv, jet, cross flow, near field analysis | Laser Induced Fluorescence (LIF) and Particle Tracking Velocimetry (PTV) are utilised to analyse the fully three dimensional complex flow which occurs in the interaction between a main flow and a jet (jet in cross flow). In order to avoid velocity versus ambiguity and to increase the dynamic range of velocity measurements, PTV is based on the analysis of successive images acquired for a long time with a standard videocamera. The trend of the jet axis is determined and the results are compared with those obtained utilising single-point measurements in other authors' experiments. |
| 204 | L. Dieterle, J. Kompenhans, U. Peiter, K. Pengel | FLOW FIELD INVESTIGATIONS ON A LARGE DELTA WING USING LSI AND PIV | delta wing, ELAC-1, laser sheet imaging, particle image velocimetry | The vortex structures on the leeward side of a large delta wing have been investigated by use of laser sheet imaging (LSI) and particle image velocimetry (PIV). The measurements were carried out in a plane crosswise to the main flow direction. With LSI, the structures of the seeded flow have been visualized. With PIV, the local distri-bu-tion of velocity has been derived from pictures of the tracer particles by means of digital cross-correlation. In both cases, the whole vortex system could be observed at Reynolds numbers Re > 107. |
| 205 | Neven Lang | PIV MEASUREMENTS IN SUB- AND SUPERSONIC FLOW OVER THE DELTA WING CONFIGURATION ELAC | particle image velocimetry, wind tunnel, delta wing, supersonic flow, subsonic flow, vapour screen, oil film technique | The roll-up of the vortex sheets of primary and secondary vortex over the leeward side of the delta wing configuration ELAC was examined using oil flow pattern, vapour screen and particle image velocimetry. Detailed information are gained concerning flow separation and reattachment by combining these methods. |
| 206 | F.Mikami, B.Chen, Y.Suzuki and N.Nishikawa | VISUALIZATION AND PTV STUDY OF TRANSIENT FEATURES OF NATURAL CONVECTION IN PARTICLE SUSPENSIONS | natural convection, particle suspension, particle tracking velocimetry (ptv), laser induced fluorescent (lif), refractive index matching | Particle Tracking Velocimetry (PTV), in conjunction with the refractive index matching technique and Laser Induced Fluorescent (LIF) tracer particles, was used to overcome the visualization problem in a particle suspension. A square test section was filled with the particle suspension and impulsively heated from the top wall while the two facing vertical walls were kept at a constant temperature. The two-dimensional velocity fields, particle distributions in a plane and the wall temperature fields were visualised simultaneously using three cameras. The results showed peculiar flow patterns such as the formation and vanishing of two-layer convection cells which were distinct from those in a clear, particle-free fluid. Sedimentation driven convection is thought to be the fundamental mechanism for the formation of these two layer convection cells. |
| 207 | Jan Mlynarczyk, Leszek Wilczynski | DESIGN OF THE END PLATES OF FOILS BASED ON THE VISUALIZATION OF STREAK LINES | airfoil, tip element, tip vortex, streak line | The paper presents the method of streak lines visualization. The aim of the research was to evaluate a simple method of tip vortex investigation and foil end plates design. The streak lines patterns coupled with the aerodynamical characteristics provide effective and adequate information about the flow phenomena occurring in the foil neighbourhood. That kind of information enables the proper design of wing tip elements. |
| 208 | O. Lysenko, N. Karbalevich, D. Ou-Yang | HOLOGRAPHIC STUDY OF HEAT TRANSFER CHARACTERISTICS OF ORGANIC LIQUIDS | differential holographic interferometry, thermal diffusivity, organic liquids. | A method based on holographic interferometer experiment and infinite plate and semi-space models is developed for thermo-physical char-acteristics of liquids. The technique was used to reveal the functional dependence of heat transfer characteristics of saturated hydrocar-bons and aromatic organic liquids on the structure parameters. |
| 209 | Kazuo Ohmi, Dao Hai Lam | NEW PARTICLE TRACKING PIV USING AN IMPROVED RELAXATION METHOD | visualization, 2-frame piv, particle tracking, relaxation method, match probability | The relaxation method using particle match probabilities is employed as an effective particle tracking algorithm in PIV measurement of fluid flows. The test images are selected from the PIV standard images open on the net, as well as bluff body wake images originating from some other sources including the authors’ own flow visuali-zations. During the test measurement, the original relaxation method by Barnard & Thompson [3] is improved in order to meet possible loss of particle images in an explicit manner. Through this im-prove--ment, the performance of particle tracking becomes more satisfactory. |
| 210 | A. F. Aboulazm | EXPLORATORY FLUID VISUALIZATION TEST IN A LARGE FLUME TANK | large flume, flow visualization | This paper describes exploratory flow visualization experiments with an idealized submarine hullform in the Circulating Water Channel (Flume Tank) at the Marine Institute of Memorial University, Canada. The tests were static in nature with variations of incident angle and flow speed. The Reynolds number was in the range 0.3 to 2.5 million based on hull length. Dye injection and air bubble techniques were used to visualize flow in the field of the model, and tuft and wet paint techniques to determine limiting streamlines on its surface. The most effective technique was dye injection in the first case and wet paint in the second. The air bubble technique was not successful because large bubble size resulted in an excessive effect of buoyancy. The flow pattern in each case was recorded using still and video cameras, and selected pictures are shown in this report. |
| 211 | J.E.S. Venart, A.C.M. Sousa and D.G. Tachell | FLIXBOURGH; A CFD STUDY | natural convection, particle suspension, particle tracking velocimetry (ptv), laser induced fluorescent (lif), refractive index matching | The 1974 Flixbourgh UVCE accident is reviewed in light of new information regarding the possible mechanism for the initiating event and its follow-on consequences. A series of transient CFD simulations was performed using the Flomerics ‘FloVent’ code to estimate the formation of the lower and upper flammable limit envelopes of the accidently discharged cyclohexane cloud. The studies considered a period of 30-40 seconds preceding the explosion. The study shows that a ‘two-step’ failure of the dog-leg pipe and its bellow attachments is a more probable event sequence than that accepted, albeit reluctantly, by the Court of Inquiry. |
| 212 | Tomasz S. Wisniewski, Tomasz A. Kowalewski, Marek Rebow | INFRARED AND LIQUID CRYSTAL THERMOGRAPHY IN NATURAL CONVECTION | infrared thermography, liquid crystals thermography, natural convection | The aim of the presented study is to test the simultaneous application of two acquisition methods, namely Particle Image Velocimetry & Thermometry combined with Infrared Thermography in an experimental investigation of natural convection. The first, based on liquid crystals tracers, allows full field temperature and flow analysis; the second is used to monitor Thermal Boundary Conditions at external non-isothermal walls bounding the flow domain. Experimental and numerical studies have been made for transient and steady natural convection in a differentially heated cube filled with water. The analysis is carried out for pure convection of water in the vicinity of the freezing region (cold wall temperature Tc= 0oC), and for convection of water accompanied by freezing. |
| 213 | A. Bredebusch, H. Burkhardt, U. Lackermeier, J. Werther | APPLICATION OF DIGITAL IMAGE PROCESSING METHODS FOR THE ANALYSIS OF FLOW STRUCTURES IN CIRCULATING FLUIDIZED BEDS | circulating fluidized bed, high speed video, image processing | This paper describes experiments to investigate the flow structure at the wall region of a Circulating Fluidized Bed (CFB). A high-speed video camera is used to visualize the flow structure through a transparent silica section. The usage of an image intensified camera makes it necessary to preprocess the images. The image sequences show that there is no homogenous flow of solids downward. To investigate the flow structure two different methods to estimate the velocity of the structures automatically are used. One method is gradient-based and the result is a two-dimensional field of velocities that show that there is turbulence in the flow. The fourier-based method delivers the component of the velocity in main flow direction but even here a two-dimensional field of measurements is computed. Investigations with different parameters show that at higher velocities the down-flow is slower and more upward turbulence occurs due to gas eruption. |
| 214 | V.M.Fomin, T.Alziary de Roquefort, A.V.Lebedev, A.I.Ivanchenko | STREAMWISE ELECTRIC DISCHARGE IN A SUPERSONIC GAS FLOW | supersonic flow, gas, electric discharge. | A self-maintained electric discharge in a supersonic gas flow may be of interest for the investigation of several gasdynamics problems, and in particular can be used for controlling the flow around aerodynamic bodies by means of local changes of physical properties of the gas [1, 2]. However the spatial-energetic characteristics of the discharge have been poorly studied so far and it seems that there is presently no publication devoted to this type of phenomena in supersonic flow. This paper presents the first results of an experimental study of the spatial energetic structure of the discharge and of its influence on the gas flow around the body. |
| 215 | Muhammad M. Rahman, Jose L. F. Porteiro, and Steven T. Weber | NUMERICAL VISUALIZATION OF SELF-SUSTAINING FLOW OSCILLATIONS IN COUNTERBALANCE VALVES | flow induced noise, hydraulic counterbalance valve, CFD, data animation | This paper reports a numerical visualization study of oscillatory flow field that contributes to noise in a hydraulic counterbalance valve. Under low flow, high-pressure drop conditions, these valves produced a high frequency, monotone noise due to shear layer instability. Experiments showed that the squeal had a primary frequency of 5300 Hz, with lower amplitude harmonics at 10530 and 15800 Hz consistent with oscillatory shear layer, resonant cavity, sound generation mechanism. Numerical simulations of the oscillatory flow within the counterbalance valve were conducted by solving equations for the conservation of mass and momentum. Animation of these results showed that the areas of recirculation grew and contracted with time. In order to eliminate the relative influence of the resonant cavity on flow instability, manipulation of the oscillating shear layer, by geometric modification, was required. The disrupted free stream behavior was verified by numerical simulation of the modified geometry. |
| 216 | Tetsuhiro Tsukiji, Ken-ichi Hori, Hidemasa Tsurumaki | FLOW VISUALIZATION OF ER FLUIDS BETWEEN TWO PARALLEL PLATES | flow control, flow visualization, multiphase flow, electrorheological fluids, unsteady flow | Microscopic behaviour of ER (Electro-rheological) suspension structure between two fixed electrodes was visualized using a high speed video camera, with a microscope viewing system, under the application of electric fields and for constant flow rates. The ER fluids used in the present study consisted of cellulose suspended in silicone oil. Two kinds of sine-wave electric fields were used and flow visualization conducted. The averages and the amplitudes of the pressure drop were measured and dependence of the pressure drop on electrical excitation frequency was investigated. |
| 217 | S. Isaev , P.Baranov, A. Usachev, D. Frolov | NUMERICAL IDENTIFICATION OF TWO- AND THREE DIMENSIONAL ORGANIZED VORTEX STRUCTURES | organised structures, vortex structures, two dimensional, three dimensional | This study is devoted to numerical visualization of organised vortex dynamics. The vortex mechanisms of drag reduction and head stability of a cylinder with coaxial disk is analysed on the basis of a numerical solution of the Navier-Stokes equations. Analogically the numerical study of large-scale vortices generated in vicinity of a deep spherical dimple on the smooth plate is made at the moderate region of Reynolds number. At last, some results concerning incompressible flow around cylinder with passive and active vortex cell are presented. |
| 218 | F. Scarano, G. Cardone, M. L. Riethmuller | TURBULENCE ANALYSIS OVER A BACKWARD FACING STEP WITH DIGITAL PIV | piv, turbulence, bfs | An improved algorithm for digital image processing has been applied to analyse digital particle image velocimetry (D-PIV) recordings of the turbulent flow over a backward facing step (BFS) at a Reh=5000. The measurement domain includes the whole separation region. The image processing algorithm aims at de-coupling space resolution from the dynamic range of the technique. The data analysis describes the turbulent features of the flow by means of its statistics. In addition to this, the instantaneous features of the flow are investigated by means of an algorithm developed “ad hoc” for vortical structure visualization. Results from the statistical analysis of turbulence are compared with available Direct Numerical Simulation (DNS) and LASER Doppler Velocimetry (LDV) data available on the same subject. |
| 219 | R. J. Adrian, K. T. Christensen, S. M. Soloff, C. D. Meinhart | DECOMPOSITION OF TURBULENT FIELDS AND VISUALIZATION OF VORTICES AND TURBULENT MOMENTUM TRANSPORT | decomposition, visualization, vortices, turbulent stresses | Several types of decomposition techniques exist for revealing the underlying structure in two- and three-dimensional velocity fields obtained by experiment and computation; however, it is unclear which is most appropriate. Traditionally, Reynolds decomposition and vorticity contours are used to visualize the eddies, but several other methods, including Galilean (constant convection velocity) and Large Eddy decompositions, along with swirling strength contours, are found to be superior in visualizing vortices visualization of turbulent stress events in different reference frames can be misleading. In wall-bounded flows, a Q2 event in one frame can be seen as a Q4 event in another. However, it is shown that the divergence of the turbulent stresses in the Reynolds decomposed field and the Galilean decomposed field are equivalent for wall-bounded turbulent flows. |
| 220 | G. Lamanna, B. Prast, M.E.H. van Dongen | EXPERIMENTAL AND NUMERICAL STUDY OF SUPERSONIC EXPANSION FLOW WITH CONDENSATION | condensation, droplet size, supersonic flow, experimental and numerical flow visualization | Condensation effects in a water vapour /nitrogen mixture, flowing through a Laval nozzle, are discussed. Both steady and unsteady flow conditions have been visualised by means of holographic interferometry and a light extinction method. The experimental data have also been compared with numerical simulations, showing a very good agreement in the steady case. For the unsteady regime some promising preliminary results concerning the determination of droplet sizes and number densities are presented. |
| 221 | B.S. Rinkevichius, A.V. Stepanov, A.V. Tolkachev | VISUALIZATION OF GAS BUBBLES MOTION IN ACOUSTIC FIELD | flow visualization, laser sheet, laser Doppler anemometer, gas bubbles | A Fiber Optics Laser Sheet (FOLS) with varying width and thickness and a Fiber Optics Laser Doppler Anemometer (FOLDA) with a varying fringe spacing were used for visualization and investigation of movement of gas bubbles which appeared in water under action of ultrasound. Bubbles complicated be-haviour as levitation, translation, rotary, and oscillatory motion under ultrasonic field and the Archimedes' force was studied. The trajectories, sizes, and velocities of the bubbles has been studied. |
| 222 | N. Fujisawa , R. Saito, S. Onuki | CALIBRATION TECHNIQUES OF LIQUID CRYSTAL THERMOMETRY AND ITS APPLICATION TO THE MEASUREMENT OF TEMPERATURE FIELD IN A HEATER UNIT | flow visualization, digital image processing, liquid crystal, temperature measurement, calibration, heater unit, automobile | The performance of color to temperature transformation of the encapsulated liquid crystal particles suspended in a liquid flow has been evaluated by using the calibration techniques with H, H/I and HSI neural networks. The measurable temperature range and the calibration errors ar e both improved by the H/I and HSI calibrations, in comparison with the H calibration. The temperature measurements of thermal flow field in a heater unit have been studied by the application of liquid crystal thermometry. The H/I calibration combined with the intensity correction technique is successfully applied to the color to temperature transformation of the visualized image. The measured temperature distributions indicate the flow mixing characteristics of the main and heater flow in the heater unit at various mixdoor angles. |
| 223 | Kazuo Ohmi, Dao Hai Lam | NEW FLEXIBLE CROSS CORRELATION PIV USING A DP MATCHING METHOD | visualization, 2-frame piv, cross-correlation method, dp matching, software algorithm | A DP matching method is introduced into the widely used cross correlation algorithm in PIV systems. This matching method is flexible to a small extent of rotation and/or shear deformation of local image templates between which the cross correlation function is evaluated. It is therefore expected that the primary disadvantage of the cross correlation method may be reduced with this method. The benchmark test is conducted on the PIV standard images open on the net, as well as bluff body wake images originating from the authors’ own fluid experiment. The results of this new algorithm are satisfactory on the whole, as long as noise components of the input images do not interfere with the pixel-by-pixel matching. |
| 224 | Kuniaki Toyada, Yusuke Muramatsu, Riho Hiramoto | VISUALIZATION OF THREE-DIMENSIONAL VORTICAL STRUCTURE OF A CIRCULAR JET EXCITED BYAXIAL AND AZIMUTHAL PERTURBATIONS | jet, visualization, excitation, vortex, three-dimensional structure, entrainment, mixing, diffusion | The three-dimensional vortical structure of a circular water jet was investigated by a flow visualization technique. The jet was excited by axial and azimuthal perturbations to enhance the large-scale axisymmetric and streamwise vortices. A laser fluorescent dye and a laser sheet were used to visualize the vortical structure, and the whole view of the structure was captured by scanning the laser sheet in the streamwise direction. The result gave us useful information on the details of the complicated vortical structure and of the entrainment, mixing and diffusion mechanism in the jet. |
| 225 | F. Y. Wang, M. M. J. Proot, J.-M. Charbonnie, P. M. Sforza | INTERACTION OF A JET WITH LEADING EDGE VORTICES | vortex-wake, jet plume, vortex method | Preliminary wind tunnel results for the interaction between the vortex-wake of a 75 degree leading edge sweep delta wing and a circular jet issuing from a tube parallel to the centerline of the wing are presented. The ratio of jet diameter to the span at trailing edge of the delta was 5.3 percent and the ratio of jet speed to free stream speed was fixed at 2. The experiments were carried out under incompressible condition at a free stream Reynolds number based on root chord of 2.04E5. The corresponding Reynolds number for the jet based on its orifice diameter and bulk velocity is 5500. A laser light sheet flow visualization technique was used to demonstrate that the vortex interaction can substantially increase the jet spread rate, a result that has important practical implications. An engineering model for the interaction process based on vortex dynamics is shown to provide a good qualitative description of the observed flow behaviour. |
| 226 | G. E. A. Meier | NEW OPTICAL TOOLS FOR FLUID MECHANICS | optical tools, fluid mechanics, pressure sensitive paint, piv, ldv | Flow visualization has a special meaning in fluid mechanics. Unsteady three dimensional flow fields need a visual display of experimental as well as theoretical results. Especially in experiments optical visualization techniques often lead to completely new insights into flow phenomena. Some discoveries which have been made this way are described in this review. Topics considered in detail are vortex obstacle interaction, Particle Image Velocimetry, long range Laser Doppler Velocimetry and Pressure Sensitive Paint. |
| 227 | R.C. Hendricks, M. Athavale, S. Lattime, M.J. Braun | VIRTUAL AND EXPERIMENTAL VISUALIZATION OF FLOWS IN PACKED BEDS OF SPHERES SIMULATING POROUS MEDIA FLOWS | porous media, virtual visualizaion, experimental visualization | A videotape presentation of flow in a packed bed of spheres is provided. The flow experiment consisted of three principal elements: (1) an oil tunnel 76.2 mm by 76.2 mm in cross section, (2) a packed bed of spheres in regular and irregular arrays, and (3) a flow characterization methodology, either (a) full flow field tracking (FFFT) or (b) computational fluid dynamic (CFD) simulation. The refraction indices of the oil and the test array of spheres were closely matched, and the flow was seeded with aluminum oxide particles. Planar laser light provided a two-dimensional projection of the flow field, and a traverse simulated a three-dimensional image of the entire flow field. Light focusing and reflection rendered the spheres black, permitting visualization of the planar circular interfaces in both the axial and transverse directions. Flows were observed near the wall-sphere interface and within the set of spheres. |
| 228 | Luigi de Luca, Carosena Meola | VISUALIZATION OF STANDING WAVES ON 2D LIQUID SHEETS | liquid sheet, absolute instability, standing waves | It is known that self-sustained resonance (global instability) may appear when the system exhibits a region of local absolute instability which is sufficiently large. In this context, an experimental work is made to ascertain the theory of Chomaz et al. about two-dimensional non-uniform sheet flows. The emphasis is on the determination of the vertical location where the local Weber number equals unity because this yields the extension of the absolute instability region. Such a location is determined by observing the standing sinuous waves generated by an obstacle placed normally to the sheet and by measuring the angle between the tangent to the wave at the obstacle and the vertical direction. A liquid sheet issuing from a two-dimensional nozzle in still air under the gravitational field is considered and tests are carried out for varying the liquid, the nozzle exit width and the position of the obstacle. A major result is that the sheet “can live” in the presence of a local absolute instability. |
| 229 | B. Gampert, J. Domjahn, T. Eich | MECHANISM OF THE OSCILLATING RAYLEIGH-BÉNARD CONVECTION | Rayleigh-Bénard convection, oscillating instabilities, laser doppler velocimetry, light sheet technique, particle image velocimetry | In this work the oscillating Rayleigh-Bénard convection was measured with laser Doppler velocimetry, holographic interferometry, light sheet technique and particle image velocimetry. The results of the different techniques confirm the hypothesis of Howard [3] that instabilities of the thermal boundary cause the oscillatory convection. |
| 230 | A. M. Fincham, H. Didelle | EXPERIMENTAL QUANTITATIVE FLOW VISUALIZATION USING 3D DPIV | 3d piv, quantitative flow visualization, Coriolis effect | The LEGI-CNRS/UJF/INPG laboratory “Coriolis”, contains the world largest rotating table, primarily designed to perform geophysical fluid dynamics experiments. The table is fitted with a 14 m diameter by 1.2 m deep circular tank. Imaging Velocimetry (IV) techniques adapted to large measurements areas (4m by 3m for example) are required to properly exploit this unique facility. Careful optimization of all imaging and experimental parameters combined with the use of a robust processing system allows accurate measurements of 2D planar velocity fields and their derivative components using standard resolution cameras. The large size of the measurement areas in the Coriolis tank permits the study of large slowly moving vorticies that get their Reynolds number from the length scale and have very small absoute velocities. |
| 231 | J.A. Tornero, I. Simó, J.M. Bergadá, E. Valencia, L. Coll | FLOW CHARACTERISTICS IN A JET SPINNING NOZZLE | Jets spinning process, fluiddynamic, yarns | The work presented, is focused on the study of the flow characteristics in the second nozzle of a pneumatic spinning process used to produce yarn. In the first part of the work, a ten times bigger model of the second nozzle is made, axial and tangential speeds in different positions along the nozzle axis are measured using a laser-Doppler velocimeter . From the experimentation it’s clearly seen the decay of the swirl along the axis.In the second part of the work, a CFD model of the nozzle is developed, experimental results and the results obtained via modelisation are discussed. |
| 232 | Gérard Poitras, Laurent Brizzi, Jean-Louis Bousgarbiès, Yves Gagnon | NUMERICAL AND EXPERIMENTAL VISUALIZATION OF THE FLOW OVER OBSTACLES | vortex method, laser tomography, obstacle, wind | The work presented in this paper is related to the study of fluid flows over two-dimensional obstacles inside a channel. The numerical results are obtained from a numerical algorithm based on vortex methods combined to a mixed Eulerian-Lagrangian scheme. On the other hand, experimental flow visualizations using laser tomography are performed on the same geometries inside a water channel. Two configurations are studied: a square obstacle with a base ($b$) and a height ($h$) of the same dimension ($b/h=1.0$) and an obstacle with a base that is twice the height of the obstacle ($b/h=2.0$). In all cases, the Reynolds number of the flow is $400$, based on the height of the obstacles and the freestream velocity. For both configurations, the numerical flow visualizations are compared to experimental flow visualizations with the objective of validating the numerical algorithm and to allow a better understanding of the flows. |
| 233 | S. Fu, Y. Wu | QUANTITATIVE ANALYSIS OF VELOCITY DISTRIBUTION FROM SCHLIEREN IMAGES | velocity measurement, schlieren system, and image motion detection | This paper presents a novel technique of analysis of velocity distribution of a fluid field using image sequences taken from a Schlieren apparatus. The displacement of each element of the fluid was obtained from the Schlieren images and then the value and direction of velocity and acceleration of the element were derived. In contrast to the PIV techniques, the presented technique holds the advantage in the situation where the tracing particles are difficult to be introduced or be identified. Buoyant flows produced from gas fires were used as case studies. The schlieren apparatus set up for the study was a modified positive-negative grid system. The velocity distribution obtained from the image analysis technique was compared with experimental study of the flow field. The application potential of this technique was discussed. |
| 234 | Chr. Klein, R.H. Engler | VISUALIZATION OF AERODYNAMIC EFFECTS USING PRESSURE SENSITIVE PAINT (PSP) | pressure sensitive paint (psp), transonic flow, double-delta wing model, vortex structures, Kelvin-Helmholtz instabilities | A two-dimensional and non-intrusive operating optical pressure measurement system PSP (Pressure Sensitive Paint) is described. The PSP technique can be used to realize absolute pressure measurements on a surface of a model and in addition to evaluate quantitative aerodynamic flow phenomena. The PSP system was tested in the Transonic Windtunnel of the German Aerospace Center in Göttingen (TWG) under real flow conditions. Instantaneous pressure distributions are recorded in almost real time on a three-dimensional double-delta wing model so that the recognition and analysis of the vortex dynamics on the model surface is possible. Even the vortex breakdown process as well as the fine structured Kelvin-Helmholtz instabilities and secondary vortex structures can be detected by this measurement technique. |
| 235 | L Sastry, D R S Boyd, R F Fowler and V V S S Sastry | NUMERICAL FLOW VISUALIZATION USING VIRTUAL REALITY TECHNIQUES | numerical flow visualization, virtual reality, computational engineering, unsteady flow, turbulence, vorticity | This paper describes the initial results from a case study for visualising and interacting with flow simulation data within a virtual environment. The objective is to demonstrate the efficacy of combining the real-time immersive interaction afforded by the virtual environment with conventional visualization techniques to gain greater insight into flow patterns. Future directions are discussed. |
| 236 | C. Cornaro, A. S. Fleischer and R. J. Goldstein | JET IMPINGEMENT ON CONCAVE AND CONVEX SURFACES | flow visualization, jet impingement, curved surface. | The present study provides insight into the interaction of an impinging jet with concave and convex cylindrical surfaces at high relative curvatures by means of flow visualization. Tests have been performed with a jet issuing from a straight tube at different Reynolds numbers (6,000, 10,000, 15,000) and different relative curvatures. The relative curvature is defined as the ratio of the tube diameter to the surface diameter and is varied by changing the tube diameter. The concave and convex surfaces consist of half of a PVC tube of 252 mm diameter . For each jet tube four nozzle to surface spacing are studied. A smoke wire technique provides a cross-sectional view of the jets. visualization of a free jet, together with jet impinging on a flat plate, are presented for completeness. Photographic records of the visualization are obtained with proper illumination of the flow field against a black background. |
| 237 | S Garg, L N Cattafesta III, M A Kegerise, G S Jones | QUANTITATIVE SCHLIEREN MEASUREMENTS OF COHERENT STRUCTURES IN PLANAR TURBULENT SHEAR FLOWS | quantitative optical diagnostics, non-intrusive measurements, shear-layer/cavityinteraction, phase-locked visualization, instability wave growth | Quantitative flow-field data were obtained in a two-dimensional shear layer spanning an open cavity with an extension of the schlieren method. The technique is based on the measurement of light-intensity fluctuations in a real-time schlieren image. Data were collected using a fiber-optic sensor embedded in the imaging screen coupled to a photodetector. Time-resolved measurements of the instantaneous density gradient at a point in the flow were thus obtained. Detailed surveys were carried out with both the optical instrument as well as a hot-wire at a Mach number of 0.25. A comparison of the results shows that the non-intrusive technique can accurately measure the growth rates of instability-waves in the initial “linear” region of the shear layer. Further, by using a microphone inside the cavity as a reference, phase-locked schlieren “movies” of the cavity shear layer modes were constructed. |
| 238 | Pier Giorgio Spazzini, Gaetano Iuso, Michele Onorato | DPIV ANALYSIS OF TURBULENT FLOW OVER A BACK-FACING STEP | back-facing step; separated flow; unsteadiness; dpiv; reverse flow | This paper deals with the complex flow in the region behind a back-facing step, analyzing results obtained in two different experiments, one performed in an air channel, the other in a boundary layer water flow. Emphasis is given to the unsteady characteristics of the flow in the recirculating region. The results presented are the probability of having forward flow close to the wall and the mean skin friction distribution downstream of the step. Flow field visualizations are also presented, evidencing the presence of a complex flow structure in the separated region. Finally, an attempt is made at providing a possible physical description of the unsteady behavior of the flow. |
| 239 | V. Balabaskaran, B.H. Lakshmana Gowda, N. Venkatasubramanian | FLOW VISUALIZATION STUDIES OVER S-BLADES | tidal power, pump-turbine, s-blade, flow visualization | A fully reversible axial flow pump-turbine is a device, which works both as a pump and as a turbine for both directions of flow. Such devices find application in tidal power plants. Double cambered S-Blade profiles have been found to give better performance for this purpose. An S-Blade profile has convex and concave curvatures on both upper and lower surfaces making the flow very complicated even at small angles of attack. In the present investigation, flow visualization studies have been carried out to get a better insight into the behaviour of flow over S-Blade profiles. The medium used is water and fine aluminium powder was used as the tracer. Studies have been carried out to get the influence of maximum camber and maximum thickness at angles of attack varying from -80 to +80. |
| 240 | Minoru Maeda, Keiji Sakohara, Atsushi Bando, Shuntaro Murakami | SOUND INTENSITY IN THE PIPE WITH ONE DISCONTINUOUS JUNCTURE | piping system, sound intensity, contracted juncture, sound power flow, acoustic vortex | In this paper, the sound intensity distribution in the pipe before the abruptly-contracted juncture is described. The patterns of sound power flow made with the intensity vectors are clarified in connection with the contraction ratio and frequency. |
| 241 | Gregory Toker and Daniel Levin | REAL TIME HOLOGRAPHIC SHEARING INTERFERENCE TECHNIQUE FOR WIND TUNNEL FLOW FIELD TESTING | Real time holographic shearing interference technique, wind tunnel, flow field testing | A novel real-time holographic interference technique, developed for wind tunnel testing is presented. The optical scheme of diffraction shearing holographic interferometer is based on a conventional Z type single pass schlieren layout. It is tolerant to both mechanical vibrations and schlieren-grade optical quality tunnel windows, and allows to gain a finite width as well an infinite background fringe pattern, which are free of optical aberrations. A series of preliminary experiments conducted with the supersonic flow over a model shows that the proposed diagnostic approach provides high accuracy of flow visualization, and demonstrates the potential for acquiring density gradient data extracted from the interferogram. The application of the real-time holographic shearing interferometry to flows in real wind tunnel facilities seems promising and easy applicable. |
| 242 | K. A. Bütefisch, H. Vollmers , V. Schmidt | FLOW VISUALIZATION AND DENSITY DETERMINATION ABOVE A DELTA~WING BY MEANS OF PLANAR INTENSITY DISTRIBUTION OF RAYLEIGH SCATTERED LASER LIGHT IN THE TRANSONIC WIND TUNNEL GÖTTINGEN | Rayleigh scattering, density measurement, transonic flow | In order to show whether Rayleigh scattering from gas molecules of a wind tunnel flow field is applicable for the acquisition of density data in the case of aerodynamically relevant flow problems, initial tests in a Ludwieg Tube at a Mach number 6.8 have been performed. Based on the experiences during these first tests, the quantitative determination of the density field above a delta~wing has been performed at Mach numbers between 0.5 and 1.4 in the transonic wind tunnel of the DLR G\"ottingen. Three-dimensional density fields with a resolution of about 1\% have been obtained. |
| 243 | Bruno Auvity, Marc Bellenoue | VORTEX STRUCTURE GENERATED BY A TRAIN TUNNEL ENTRY NEAR THE PORTAL | laser sheet imaging, Schlieren, vortex, boundary layer, pressure waves, high speed train | An experimental study has been carried out by means of a 1/140 th scale model of a high speed train entering a tunnel. visualizations, using a laser sheet, have revealed the existence of a vortex, developing at the tunnel entrance, when a train enters. The interaction between the boundary layer which exists on the train and the exiting jet has been clearly defined. The boundary layer makes an important contribution to the vortex bursting, especially for lower train speeds. The exiting jet creates a pressure gradient on the train body and, consequently, affects the boundary layer. The thickening and the core co-ordinates of the vortex are independent both from the train speed and train nose geometry but depend on a non-dimensional time scale. |
| 244 | Mark A. Fry | SAFETY ANALYSIS USING EXPLOSIVE PREDICTION SOFTWARE CONTAINING GRAPHICAL DISPLAYS | Explosions, detonations, deflagrations, visualization | The complexity of explosively driven shock waves near structures, both inside and outside, has been simplified usilg three-dimelsimlal flmw visualizatiml. The dependent variables that govern the physics of detonations and deflagrations can be viewed graphically in a time-dependent manner, allowing conclusions to be reached quickly and accurately. The effects of explosions can be mitigated by first knowing the amount of damage that can be incurred and then applying siting and shielding techniques. Flow visualization becomes extremely important in order to achieve maximum protection with minimum cost. Compliance with fire codes does not guarantee against devastating losses resulting from a fire or explosion. Potential fires and explosions within process facilities can be modeled to greatly reduce uncertainty and costs associated with protective systems. |
| 245 | Toyoaki Yoshida | SOME CONSIDERATIONS ON IMAGE RECONSTRUCTION OF MATRIX METHOD CT | computed tomography, matrix method, non-destructive inspection, turbine blade, gamma rays ct, betterment of image quality, noise reduction, beam coverage | The author's group once introduced a matrix method computed tomography (CT). It was applied to a hollow turbine blade non-destructive inspection with the use of gamma rays The present work concerns betterment of image quality from the viewpoints of reduction in noise that is included in original projection data and way for counting coverage of an electro-magnetic beam over individual unit element of an object. As a result, a combination of conventional and simple processing indicates most desirable quality, contrary to expectations. |
| 246 | C. Migeon, I. Boue, G. Pineau and A. Texier | CHANNEL-FLOW EFFECTS UPON A CYLINDRICALSQUARE-SECTION CAVITY | cavity flow, starting vortex | In this paper an experimental investigation of starting vortex flow inside a square-section cavity, submitted to a channel-driven shear stress, was conducted for a Reynolds number of 1000 and for a cavity aspect ratio of 2 :1. Effects of the channel gap on cavity recirculating structures were analyzed by considering six gap values ranging from 0 (Lid-driven cavity case) to infinity (outer-stream-driven cavity). Observations were made by flow visualization in cross- and span-views using two complementary methods : the continuous tin-ribbon electrolysis (dye emission) and the classical particle-streak methods respectively giving information on mass and momentum transport. In the middle cross-section, particular attention is given to the precise birth and development of primary and secondary eddies through analysis of topological (eddy sizes) and kinematic (velocity distributions) data. In addition, spanwise visualizations show how three-dimensionality extends progressively from the cavity end-walls to the whole area. |
| 247 | F. Eisfeld | INVESTIGATION OF THE SPREADING OF THIN LUBRICATION OIL FILMS | Lubrication, oil film, spreading, film thickness, oil consumption, engine, deep-draw, fluorescence method. | For economical anl ecological reasons it is important to minimize the wear and also the oil consumption by an optimal lubrication. Therfore investigations were made to make visible the spreading and the thickness of the lubrication film between piston and zylinder wall of an engine. For this reason a test set-up was developed to simulate the conditions in an engine. Moreover also the spreading and the motion of the lubrication film by the deep-draw between die cast and sheet iron could investigated with the same set-up. To make visible the oil film the oil was provided with a little quantum of fluorescence dye. The test method, the optical and the mechanical test set-ups are described. |
| 248 | Tadayuki Sugimori, Kunio Baba, Takehiko Fujiwara, Yoshio Ishii, Kazuhiro Watanabe, Yuzuru Kubota, and Gen Marubayashi | MEASUREMENTS OF A FLOW FIELD OF CONICAL SPRAY USING A LASER SCANNING VISUALIZATION SYSTEM | surface visualization, laser-scanning, image analysis, spray jet | This study represents a novel visualization technique for non-axisymmetric flows using a high speed laser beam scanner. Conical spray jet has been visualized along its curved surface. |
| 249 | Yoshio Ishii, Noriyo Sakurada,Tadayuki Sugimori, Kazuhiro Watanabe, Yuzuru Kubota, Katutoshi Nagano | VISUALIZATION OF INFRARED HIGH POWER LASER BEAM FOR IN-LINE MONITORING USING AN ULTRAVIOLET CCD CAMERA | laser visualization, ultraviolet image, temperature sensitivity | This paper attempts an alternative method to visualize high power invisible beam profile from the temperature distribution of highly energetic molten pool. The system using an ultraviolet CCD camera has been found to be attractive and very useful for the in-line monitoring in various laser material processings. Images of the contour map of the laser irradiated target area are presented, from which the reconstruction of 3-D laser profile is obtained. |
| 250 | Dirk Engelmann, Christoph Garbe, Michael Stöhr, Peter Geißler, Frank Hering, Bernd Jähne | STEREO PARTICLE TRACKING | stereo particle tracking, stereo calibration, stereo correlation | Particle Tracking Velocimetry (PTV) has become a standard technique frequently applied in flow field diagnostics. This article presents a novel technique which combines the strength of well known 2-D PTV with stereo calibration and correlation techniques to obtain 3D Lagrangian velocity fields. The here presented stereo correlation tech-nique is fundamental for 3-D PTV. In addition with a sub pixel precise stereo calibration tech-nique it is possible to reconstruct, timely and spatially resolved, paths of particles represent-ing the flow characteristic. The stereo correlation technique uses the resulting trajectories from PTV. Therefore 2-D trajectories instead of spatial position for single particles are correlated. This allows to keep the set-up simple with a minimum number of two cameras and also speeds up the 3-D evaluation compared to multiple camera set-ups. First results of flow visualization with particles and air bubbles are presented. |
| 251 | A. Cenedese | EULERIAN AND LAGRANGIAN VELOCITY MEASUREMENTS BY MEANS OF IMAGE ANALYSIS | Eulerian, Lagrangian, image analysis | The most common velocity measurement techniques, based on image analysis (PIV), determine the velocity by correlation of a portion of the digitised images, and give an Eulerian description of the investigated field. Particle Tracking Velocimetry (PTV), based on the recognition of trajectories of seeding particles, only furnishes an Eulerian description provided the trajectories are shorter than the characteristics scale of the phenomenon. If particles are tracked for a longer time, a Lagrangian description is obtained. Consequently, in order to successfully evaluate Lagrangian statistics, a long series of single-exposed images has to be acquired. PTV has been utilised in order to analyse different laboratory simulations of flow fields which assume a particular importance in environment applications. |
| 252 | Hiroyuki Hirahara, Masaaki Kawahashi | VISUALIZATION OF THE VELOCITY RELAXATION PROCESS BEHIND A SHOCK WAVE PROPAGATING IN MIST | shock wave, mist flow, relaxation, optical measurement, expansion-shock tube | Optical measurement of velocity relaxation process in droplets-gas flow has been carried out with a spatial filtering method. A mist flow was produced by an adiabatic expansion of a mixture of water vapor and N2 gas. Droplets were accelerated by a plane shock wave. Experimental results were compared with numerical one. It was shown that the relaxation length decrease as shock Mach number increases. It is found that the numerical prediction is underestimated for the experimental result. |
| 253 | E. Raoui, Y. Bailly, J. P. Prenel, M. Khan | P.I.V. EXPERIMENTS AND NUMERICAL CALCULUS ON NATURAL CONVECTION IN BIDIMENSIONAL ENCLOSURES | natural convection - tomography - piv. - numerical computation - enclosure | The study of natural convection is of great interest in numerous engineering applications. Particularly, natural convection in an enclosed cavity filled with fluid is considerably studied in recent researches. The aim of this paper is to provide experimental results and to compare them with those obtained with the developed computational method. The investigated flow takes place in a bidimensional rectangular enclosure with a vertical heated wall. In a second part, this study shows the influence of an obstacle on the flow structure. The main experimental technique consists of laser tomography. The results of visualizations are performed by using an image processing software to measure geometrical parameters. In order to explore the velocity field, P.I.V. experiments have been used. The numerical calculation strongly depending on the boundary conditions, several thermoelectric sensors are located in the heated wall. |
| 254 | Christian Chauvet | EVALUATION OF WATER SPRAY AND SPLASH THROWN UP BY HEAVY ROAD VEHICLE | water spray and splash, camera calibration, road testing | An experimental study of the water spray and splash thrown up by heavy road vehicles was undertaken in the Jules Verne climatic wind tunnel in Nantes. With reference to wind tunnel experiments, full scale testing were conducted on the road with a real truck. Thanks to continuous video recordings of the testing, a qualitative and semi-quantitative assessment of the phenomena was achieved. An original image processing procedure was developed to perform a correction of the transient perspective induced by the imaging technique. This analysis was compared with a 3D rendering of the water clouds obtained by optical laser tomography. |
| 255 | U. Kertzscher,K. Affeld, L. Goubergrits, A. Ziemann | OPTICAL METHOD TO ASSESS THE WALL SHEAR RATE IN SMALL DUCTS | wall shear rate, flow visualization, piv, Hagen-Poiseuille flow | A new method to measure the wall shear rate is presented. The wall shear rate in general is difficult to assess, especially in small and curved ducts, such as models of natural blood vessels. The research of the wall shear rate in these models is needed for the clarification of the causes of a vessel disease, namely atherosclero-sis. The otherwise widely used Laser Doppler Velocimetry (LDV) is not suitable, because it does not permit a measurement at the wall closer than 0.2 millimeter, which is large in comparison to a vessel diameter of 4 millimeters. In addition, the measurement is performed in discrete points, making it time consuming to assess a whole field. The Particle Image Velocimetry (PIV) permits one to measure velocity in a field; however, it also does not perform well in the vicinty of a wall. The new method overcomes theses prob-lems. Like the PIV method it makes use of parti-cles, which are mixed with the fluid. |
| 256 | Carolyn R. Mercer, Nasser Rashidnia | COMMON-PATH PHASE-STEPPED INTERFEROMETER FOR FLUID MEASUREMENTS | interferometry, phase stepping, temperature | The liquid-crystal point-diffraction interferometer is a new phase-stepped, common-path interferometer. A microsphere in a liquid crystal layer is used to locally generate a reference beam and phase-shift the object beam. The result is an interferometer that provides quantitative, high-density data in relatively high vibration environments. This paper describes a comparison between the liquid-crystal PDI and a phase-stepped Mach-Zehnder interferometer. Both were used to simultaneously measure temperature distributions in an oil bath. Very good agreement between the data from both interferometers is shown, and the common-path interferometer is shown to be more robust in the presence of vibrations. |
| 257 | Akikazu Kaga, Katsuhito Yamaguchi, Akira Kondo, Yoshio Inoue | COMBINATION OF PIV DATA WITH CFD USING COST FUNCTION METHOD | flow visualization, flow estimation, turbulence model | A technique to estimate a flow field which is based on observation result and also satisfies fundamental equations of fluid dynamics approximately, by combining Particle Imaging Velocimetry (PIV) and Computational Fluid Dynamics (CFD) is discussed. It is shown that the effect of wrong boundary conditions assumed in combining process is reduced by data but the inaccuracy in the expressions of fundamental equations due to finite difference approximation is not reduced by data, through the application of this technique to Burger's equation. The concrete procedure of our Cost Function(CF) method which is consistent with our CFD model and some results of the applications are also presented. It is demonstrated that the combination technique is effective in estimating an natural flow field with no data absence point from PIV data. |
| 258 | Aaron Drake, Russell V. Westphal, Robert A. Kennelly, David M. Driver | SKIN FRICTION DOWNSTREAM OF BOUNDARY LAYER TRIPS | oil film interferometry; boundary layer trips; transition; skin friction; wind tunnel testing | The skin friction distribution downstream of boundary layer trips has been quantitatively visualized with oil film interferometry. The technique required a single interferogram to be recorded after a line of transparent oil had been thinned by the skin friction acting on it. Digital analysis of the image allowed calculation of the local skin friction. The trip, composed of a regular array of identical elements, was placed at Rex = 105. Cylindrical and other element shapes were examined, with height-based local Reynolds numbers of 244 < Rek < 2409 and fineness values 0.3 < d/k < 50. For trips with pitch greater than 2.0, it was found that element shape, spacing, and fineness have no effect on the location for initia-tion of lateral spreading of turbulence. For Rek > 600, spreading began at the elements; this result agrees with accepted criteria for transition induced by grit-type roughness. |
| 259 | A. O. Leone, P. Marzano, E. Gobbetti, R. Scateni, S. Pedinotti | DISCONTINUOUS FINITE ELEMENT VISUALIZATION | visualization, high-order finite elements, discontinuous fields, mesh refinement | The aim of this work is the study and the implementation of appropriate visualization techniques for high-order discontinuous finite element data in two and three-dimensions. In particular, we are dealing with field discontinuity and deformed cells. Such data are produced for example by chemical simulations, by fluid dynamics simulations, or, in general, anywhere high accuracy on boundary domain description is required. |
| 260 | Takashi Yumino, Haruhiko Itoh, Yoshimichi Tanida | VISUALIZATION OF SECONDARY FLOW IN A BIFURCATING TUBE | respiration, gas exchange, flow visualization | The gas transport in respiratory network is a very interesting phenomenon. In the present paper, a particular attention is paid on the characteristics of secondary flow in a dividing and combining junctions which are models of the trachea tube. The secondary flow is visualized in steady water flow by using dye-injection method and in steady and pulsating air flow by using incense stick-smoke and smoke-wire methods. Further, the gas diffusion in straight and bifurcating tubes are measured. |
| 261 | Hiroharu Kato | RESEARCH ON CAVITATION MECHANISM BY HIGH-SPEED VIDEO AND HOLOGRAPHIC OBSERVATIONS | cavitation, cavity, cloud, collapse, high-speed video,holography, hologram, nuclei | Cavitation is a phenomenon in which rapid phase change from a liquid state to a vapor state and vice versa occurs. It is important to investigate the mechanism and to obtain a countermeasure for preventing detrimental effects, such as erosion and noise. The phenomenon is characterized by its complexity and very rapid phase change. Therefore, novel observation techniques, such as high-speed video, or a holographic system are required for understanding the phenomenon. This paper presents the following experimental studies performed at The University of Tokyo. - Observation of sheet-cloud cavitation on a 2D foil using a high-speed video, which enables estimation of vaporization rate from the cavity surface - Observation of the structure of a cavitation bubble cluster using an off-axis hologram - Observation of the final collapsing stage of cloud cavitation using a high-speed video capable of acquiring 40,500 frames/sec. |
| 262 | Guido Belforte, Andrea Manuello Bertetto, Luigi Mazza, Davide Rittatore | VISUALIZATION TECHNIQUES FOR WHIRLING FLOWS IN FLUIDIC ELEMENTS | visualization, vortex valve, fluidic element. | The aim of this work is the characterisation of the flow field in a fluidic vortex element operating with water. In peculiar the aim is to individuate not intrusive techniques in order to define experimentally the fluid particles trajectories and their velocity distribution, without fluid pollution and least flow field alteration. |
| 263 | Jung Kyung Kim, Jaeyong Sung, Jun Keun Chang, Byoung Goo Min and Jung Yul Yoo | MEASUREMENT OF PULSATILE TURBULENT FLOW THROUGH POLYURETHANE HEART VALVE PROSTHESIS USING PARTICLE IMAGE VELOCIMETRY | polyurethane artificial heart valve, particle image velocimetry, hot-film anemometry (HFA), hemolysis, thrombus formation | In-vitro flow characteristics in the vicinity of a polyurethane artificial heart valve under pulsatile flow conditions have been investigated using Particle Image Velocimetry (PIV). With a triggering system and a time-delayed circuit the velocity field downstream of the valve was evaluated in conjunction with the opening behavior of a flexible valve leaflet during a cardiac cycle. Direct measurements of the wall shear stress by hot-film anemomety (HFA) were compared with the PIV data. The possi-bilities of vascular complications, such as the thrombus formation and RBC damage, could be estimated from the overall view of the instantaneous velocity and stress fields obtained. |
| 264 | Nathalie Boisaubert, Stéphane Maurel, Alain Texier | SPLITTER PLATE EFFECT ON BLUFF BODY VORTEX FORMATION | circular cylinder, semi-circular cylinder, splitter plate, near wake establishment, solid particle visualization | A 1-D long splitter plate influence on near wake establishment of two impulsively started bluff bodies – a circular cylinder (CC) and a semi-circular cylinder (SCC) (fixed separa-tion points) – is experimentally studied for a Reynolds number Re of 200. The plate is positioned along the downstream center plane at fixed gap g = 0D, 0,5D and 1D. The early vortex formation and shedding are analysed by means of solid particle visualizations. Topological observations and measurement characterising the recirculation zone geometry and flow kinematics are proposed and compared with the data related to the CC and SCC near wakes. |
| 265 | G. De Stefano F. M. Denaro G. Riccardi | NUMERICAL DETECTION AND VISUALIZATION OF VORTICAL STRUCTURES IN A CONFINED FLOW | large eddy simulation, vortex structure detection, backward facing-step | Flow visualization of turbulent confined flow results a difficult issue because of great detail of structures and their time dependent character. A survey of several criteria for the eduction of structures is presented. The application deals with the backward facing-step turbulent flow at Re=7500. |
| 266 | F. Seiler, A. George, J. Srulijes | DOPPLER PICTURE INTERFERENCE VELOCIMETRY | doppler, interference, velocimetry. | An improved technique for visualizing a velocity field in an entire plane has been developed by taking “Doppler Velocimetry Pictures” using Michelson interferometry (DPIV). The Doppler Picture gives information about the instantaneous as well as the local velocities of tracers passing a light sheet that traverses a flow. The Doppler shift of the frequency of the light scattered by tracer particles is transformed by a Michelson interferometer into varying light intensities. In version I (developed in 1981) a given initial interference fringe pattern is shifted by flow velocity gradients. Here the Doppler images are taken with a photo camera, digitalized with a scanner and evaluated by computer software. Since 1997 in DPIV version II the Doppler Picture initially shows an evenly distributed light intensity without fringes. Two complementary Doppler Pictures are taken by CCD-cameras and the images are computer processed for velocity presentation. |
| 267 | Tsutomu Adachi, Minoru Yamashita, Kenichiro Yasuhara, Tatsuo Kawai | VISUALIZATION OF THE FLOW IN THE MOVING BLADE PASSAGE OF A SINGLE STAGE AXIAL-FLOW FAN | flow visualization, moving blade, three dimensional unsteady flow, axial flow fan | Three dimensional unsteady velocities were measured near the moving blade of a single stage axial-flow fan using a hot wire probe. A stationary blade was mounted in front of fan wheel. The passage of the wake of the preceding stationary blade, its effects of secondary flow and the 'leakage' through the tip clearance gap were reconstructed on film. |
| 268 | T. Astarita, G. Cardone, G.M. Carlomagno | HEAT TRANSFER MEASUREMENTS ON A ROTATING DISK WITH A CENTRED IMPINGING JET | jets, rotating disk, convective heat transfer, ir thermography | Flow visualizations and heat transfer measurements on a rotating disk, with a rather small centred jet perpendicularly impinging on it, are performed by means of infrared thermography applied to the heated-thin-foil technique. Flow visualizations show a strong interaction between the turbulent jet and the laminar boundary layer over the rotating disk which suggests an earlier transition to turbulence. A new governing similitude parameter and a heat transfer correlation for the Nusselt number at the disk centre, which is based on this parameter, are proposed. Before transition, i.e. for low values of local radius normalised with the nozzle to disk distance, the Nusselt number profiles tend to overlap if they are normalised with the Nusselt number computed by means of said correlation. |
| 269 | Aline J. Cotel and Robert E. Breidenthal | A NEW PARAMETER FOR SURFACE FLUXES DISCOVERED FROM FLOW VISUALIZATION | persistence, stratified, entrainment, turbulence, heat transfer, skin friction | Simple flow visualization experiments of a turbulent jet impinging on a stratified interface have revealed that the entrainment rate across the interface depends on a new parameter. The vortex persistence is a measure of the stationarity of the incident turbulent vortex with respect to the interface. The persistence is proposed to play a central role anytime a vortex is near any interface, such as a solid wall. Thus heat transfer and skin friction are determined in large part by vortex persistence. |
| 270 | T. Kataoka, Y. Nakayama, E. Ando, K. Aoki | BEHAVIOR OF SMALL LIQUID DROPLET MIXED INTO SUPERSONIC JET | visualization measurement supersonic flow cleaning | With liquid crystal and semiconductor devices being refined and highly integrated, it is now inevitable to develop super precision cleaning techniques. Such a new technique is suggested to remove adhered fine particles by means of applying the impact force of droplets made to collide at high speed onto the surface of an object to be cleaned. This report is concerned with a supersonic mixing nozzle of fine fluid particles. First of all, the characteristics of a supersonic flow was visualized by the Schlieren method for the case of air only, and clarified changes in image due to the difference in the ratio of pressure outside the nozzle to pressure inside the nozzle. Then, a cone was put in a supersonic flow, the flow velocity was measured from the Mach angle of the oblique shock wave generating from the cone tip. Furthermore, the seeding method with a laser Doppler velocimeter was studied. |
| 271 | T. Leweke, C. H. K. Williamson | THREE-DIMENSIONAL DYNAMICS OF A COUNTERROTATIN G VORTEX PAIR | vortex pairs, Crow instability, elliptic instability | In this paper, we present results from an experimental study of the dynamics of a pair of parallel counterrotating vortices, which is uniform in the axial direction. We observe the existence of three-dimensional instabilities at different axial wavelengths, depending on the Reynolds number of the flow. Under the effect of a long-wavelength Crow instability, the vortices develop a growing waviness, leading eventually to the formation of periodic vortex rings. A short-wavelength instability, which occurs above a threshold Reynolds number and can be associated with an elliptic instability of the vortex cores, causes internal deformations of the vortices and, in combination with the Crow instability, leads to a faster decay of the large-scale vortical structures. Detailed visualizations of both phenomena are shown. |
| 272 | Sikorski Bogdan, Leoncini Paolo | FLOWVIS: YET ANOTHER NUMERICAL -EXPERIMENTAL VISUALIZATION SYSTEM | schlieren, interferogram, shadowgraph, oil-flow, CFD, LIC. | “Pretty” colour images of common (and not so common) CFD data visualization techniques many times don’t convince fluid-dynamicists. Among the reasons of such an approach is that many of these images simply cannot be obtained from real-life wind tunnel experiments, and it’s well known that these latter are able to directly show flow features (shock, separation/ reattachment, vortices, ...), which, instead, data representations commonly used for the visualization of numerical simulation data can point out only indirectly. The FLOVIS 4.0 visualization software tries to address these various problems. It allows immersion and treatment of digital images (photographs) in the same 3D scene as the grid data, and incorporates a few techniques allowing direct visual confrontation of the simulation and experimental data. |
| 273 | Keiichi Hanada | SWITCHING MECHANISM OF A JET ATTACHED TO THE WALL OF A FLUIDIC DEVICE, USING A NEW FLOW VISUALIZATION TECHNIQUE | switching e mechanism, vortex, fluidics, separation, Coanda m effect e | Quasi-static switching mechanism of the fluidic wall attachment device was identified with dynamic switching under some hypotheses in this paper. The switching mechanism has been the key theme in studying this device but the mechanism for this reattached fluid was not identified until this paper. It can be pointed out that the previous hypotheses of the mathematical attachment point model [1](Fig.1) were less than satisfactory. In this old model the return flow width was assumed to be zero when, in fact , it is not zero. Considering the width of the return flow, this paper indicates a new mathematical model (Fig.2). In doing so, the separation mechanism of the reattached jet became quite clear. |
| 274 | Gökhan Özkan I. Bedii Özdemir | SHOCK CHARACTERISTICS OF SUPERSONIC TWO PHASE FREE JETS | two-phase flow, supersonic flow, jets, axisymmetric shear layers, rocket exhausts | The flow process of a two-phase supersonic jet has been investigated with a particle-loaded air flow expanded to a speed of Mach number of 2 through a convergent-divergent nozzle of 20 mm exit diameter. The shadowgraph technique was used to reveal qualitative features of the near field, in particular the first shock cell, as functions of stagnation pressure and particle loadings with different inertia. They also provided the quantitative data for characteristics of the Mach disc in comparison with a single-phase jet of the same stagnation conditions. The results put in evidence that although for large underexpansion ratios, the shock characteristics of the two-phase flow become similar to that of the single-phase, the second phase in general modifies the first shock cell as if the jet is exhausted into relatively higher back pressure. |
| 275 | Mete Kayisbudak, I. Bedii Özdemir | SUPERSONIC JET WALL INTERACTIONS | supersonic flow, jet impingement, rocket and launcher interactions | The aerodynamic aspects of the flow, formed after angled impingement of an axisymmetric supersonic jet onto a flat plate, have been studied with emphasis on the shock structures and interactions with the approaching jet. The general features of the flow field were examined qualitatively by shadowgraph images for the jet which was exhausted from a convergent-divergent nozzle of 20 mm exit diameter with a Mach number of 2 and underexpansion ratio in between 1.08 and 1.60, and impinged to the plate at angles 0, 10 and 15 degrees with nozzle-to-plate distance to nozzle exit diameter ratios of 3 and 4. The results has shown that when the plate is inclined, the symmetry of the structures of the approaching jet has remained unchanged. This was also true for the plate shock in the impingement zone. The tail shock has, however, developed asymmetry with inclination in that, while it diminishes on the side where the plate shock nearly touches to the wall, it extends as to get parallel to the plate on the other side. |
| 276 | Shigeru Nishio, Nami Hirata,Taketoshi Okuno | STATISTICAL IMAGE ANALYSIS FOR THREE DIMENSIONAL VELOCITY MEASUREMENT | piv, statistical approach, three-dimensional flow measurement. | Three-dimensional flow field is measured using the statistical image analysis. The authors have developed a new image measurement technique by means of statistical analysis. The technique based on the fact that the probability of particle passing is proportional to the flow speed if the particle concentration is uniform and constant through the measurement Streamline coordinate system and particle passing of the measurement plane. Particle Image Velocimetry (PIV) offers the non-intrusive, instantaneous field measurement which gives great advantages to the experimental fluid dynamics. The three-dimensional flow field is usually measured using the stereoscopic positioning technique. It is not always easy because the system require the multi-camera system, the high-quality calibration and the large CPU time resulting the complicated algorizm. The statistical approach to the image measurement of velocity field enabled to measure the time-averaged flow speed distribution in both 2-D and 3-D flow field. |
| 277 | I Grant, M Mo, X. Pan, P Parkin, J Powell , D Hurst | COMPUTERISED ANIMATION OF PIV MEASUREMENTS AND LASER SHEET VISUALIZATION IN THE WAKE OF A PASSENGER AIRCRAFT MODEL IN A LARGE, LOW SPEED WIND-TUNNEL | piv, laser sheet visualization, EUROWAKE, passenger aircraft, wind-tunnel |
A particle
image velocimetry (PIV) and laser sheet visualization (LSV) study
of the flow behind a 1/12.81 scale model of a representative
passenger aircraft was undertaken in a 10 ft by 12 ft closed
return wind tunnel. Measurements were made in planes, normal
to the mean flow, at various downstream positions, for different
model configurations. The data images were analysed to
extract raw velocity vectors after which the data were processed
to obtain velocity measurements on a regular grid. From
this information vorticity, divergence and cross flow energy
were calculated. In addition, animations of the data were
assembled to show both typical local temporal flow variation
at one downstream plane and flow variation with downstream
distance from the model wing tip. These procedures are discussed and examples of the data sets presented. |
| 278 | Shigeru Nishio, Koji Okamoto, Tetsuo Saga, Toshio Kobayashi | STANDARD IMAGES FOR PARTICLE IMAGE VELOCIMETRY AND ITS APPLICATION ON SYSTME PERFORMANCE EVALUATION | piv, standard image, performance investigation | Standard images which aims to establish an evaluation code of Particle Image Velocimetry (PIV) are proposed, and a PIV system is applied to it. The PIV offers great advantages for the study of fluid dynamics, and a number of PIV techniques and systems have been developed. However, there are no standard evaluation tools for the effectiveness and accuracy. It is required that the PIV systems should have some standard to popularize systems for practical use. A research group (PIV-STD) organized by the visualization Society of Japan (VSJ) has developed the standard images. They are distributed using the Internet ( http://www.vsj.or.jp/piv/ ) and anyone can download the images through anonymous FTP or HTML. The developed PIV standard images can be accessed from all over the world. The 2-D and 3-D standard images including the stereoscopic image sets are prepared on the site. In the present study, the advanced standard images using the three-dimensional transient flow data are described. |
| 279 | C. Piantini, A. Imbrenda | THE BOUNDARY LAYER WIND TUNNEL OFCRIACIV-DIC AND ITS APPLICATIONIN FLOW VISUALIZATION | boundary layer wind tunnel, turbulence, light sheet visualization,wind engineering | The boundary layer wind tunnel of CRIACIV-DIC is a facility unique of its kind currently working in Italy. Its employment ranges from civil engineering studies on buildings and environmental problems investigation to fluidodynamics research on three-dimensional problems. The wind tunnel and the instrumentation developed for the study of these fields are described in this paper with a detailed insight on the flow visualization apparatus. Some works at present developing in the facility using light sheet tecnique are shown and discussed. |
| 280 | Y. Ikeda, T. Saito, J. Rohaly, N .Kuratani and T. Nakajima | QUANTITATIVE VISUALIZATION OF HIGH SPEED VORTEX SHEDDING FLOW AND ITS CHARACTERISTICS | recirculating flow, vortex shedding, flow visualization, ldv, piv | We have investigated the characteristics of the recirculating flow behind the V-gutter of a model ram combustor, first by applying laser Doppler velocimeter (LDV) measurement technique. These results indicate that velocities have bi-modal probability densities with two sharp peaks representing strong mode of oscillation whose frequency was found to be constant over the entire flow field. This oscillation was clearly due to the vortex shedding and not by any kind of resonance in the combustor dimensions. However, even we insist the existence of vortex shedding saying that the FFT peaks of LDV data are applicable to understand vortex scales, spatial images on vortices were required for the full description of the recirculating flow field. The purpose of this experimental research is to show the vortex shedding phenomenon by planar visualization and the vortex shedding and its dimensions were understood by LDV and PIV measurement. |
| 281 | Ö. Karatekin, F. Y. Wang, J.-M. Charbonnier | VISUALIZATION OF UNSTEADY WAKES | wake, flow visualization, piv, unsteady flow, vortex | Unsteady flow in the near wake of a three-dimensional bluff body is visualised in the 1000 Reynolds number range. Dye flow visualizations performed in a water tunnel showed the time dependent motion of the vortex rings created in the shear layers due to Kelvin-Helmoltz type instabilities. These experiments were complemented by Particle Image Velocimetry measurements which yield time series of instantaneous flow fields, allowing a first quantitative interpretation of the unsteady near wake flow. |
| 282 | X.Z. Huang and E.S. Hanff | GRAY LEVEL ANALYSIS OF OFF-SURFACE VORTEX visualization ON A 65 DELTA WING OSCILLAVISUALIZATIONTING IN ROLL | laser- sheet gray- level analysis, delta wing, leading-edge vortex | The off-surface flow visualization of a leading-edge vortex over a delta wing at high Reynolds number was studied. The flow was illuminated by laser sheet and recorded by high-speed video camera. Gray-level image analysis proved to be capable of obtaining quantitative results of the leading-edge vortex behavior, such as its edge, core location, breakdown location even the vortex profile. The vortex profile and its breakdown location were found much effected by the wing motions and roll angle while its core locations were found functions of roll angles but independent of motion variables. |
| 283 | Takeharu Etoh, Kohsei Takehara, Kohji Okamoto | THE PARTICLE MASK CORRELATION METHOD | ptv, particle image extraction, particle mask | For Particle Tracking Velocimetry (PTV), the particle mask correlation method that efficiently extracts particle images from image plane has been proposed. A typical brightness pattern of a particle image is referred as a particle mask. It is placed on an image plane and cross-correlation coefficient between the particle mask and the image plane is calculated. The particle mask is scanned on the image plane with the calculation of cross-correlation coefficient. The small subareas with high cross-correlation coefficients indicate central areas of particle images. The performance of the particle mask correlation method is tested. The particle mask correlation method is also applied to synthesized particle images which are provided as benchmark data for evaluation of PIV/PTV algorithms. The synthesized particle images are called “standard images”, and are provided by the visualization Society of Japan. |
| 284 | M. Kassemi, N. Rashidnia, C. Mercer | NUMERICAL/EXPERIMENTAL VISUALIZATION OF OSCILLATORY TEMPERATURE FIELDS GENERATED BY A BUBBLE | bubbles, free surfaces, thermocapillary convection, abel transform | In this paper, we study steady and oscillatory thermocapillary and natural convective flows generated by a bubble on a heated solid surface. A combined numerical-experimental approach is adopted. The temperature field is visualized using Wollaston Prism Interferometry and the flow field is observed by a laser sheet flow visualization technique. A finite element numerical model is developed which solves the transient two-dimensional momentum and energy equations and includes the effects of temperature-dependent surface tension and bubble surface deformation. Index of refraction fringe patterns predicted by the model using the Abel integral transform are compared directly to the index of refraction fringe patterns visualized experimentally using interferometry. Below the critical Marangoni number, the steady state numerical predictions are in excellent agreement with both the visualization experiments in our laboratory and recently published experimental results. |
| 285 | A.Amoresano, G.Langella, C.Noviello, F.Beretta | EXPERIMENTAL ANALYSIS OF FLAME INSTABILITY PHENOMENON IN A FUEL OIL BURNER | spray, combustion, flame instability, high speed images acquisition | Experimental remarks regarding the instability conditions of flame working in liquid nebulized fuels are following reported. The datum point is a 50000 J/s burner fed with preheated air and ambient temperature air as to the burning fluid. The atomization is mechanical and it is obtained through a whirling nozzle. In this way, it is possible to create such fluid dynamic conditions of working to pass from situation of sure flame instability to conditions of instability that is checked with continuity without neglecting any intermediate situation. The experimental remarks have been performed through a high speed television facility as the images in the present work clearly show. Excursion and frequency of flame obscillations in a research field that goes from sure stability to proved instability derive from television recordings. Therfore, they are pointed out the main fluidoynamic conditions of the jet of the supporter of combustion and the basic characteristics of the jet of the atomized fuel. |
| 286 | R. Ragucci, A. Cavaliere, M. de Joannon, C. Noviello | SPECTRALLY AND SPATIALLY RESOLVED VISUALIZATION OF EMISSION AND FLUORESCENCE PATTERNS IN A HIGH PRESSURE COMBUSTION ENVIRONMENT | spray, combustion, spectral-spatial patterns, lif, chemiluminescence | An interpretative scheme was set up that combined synergistically emission spectroscopy and laser assisted techniques to obtain unambiguous detection of either single species or classes of species. Both spontaneous and laser excited emission patterns were collected from an auto-igniting pulsed spray injected in an optically accessible pressurised flow chamber. Patterns collected in these conditions, and in the spectral range 300-600 nm, were compared to those obtained using pure reference compounds. This was in order both to evaluate experimental set-up potentials and to attribute evidenced spectral features to individual compounds or classes of compounds. |
| 287 | Yoshiyuki Suzuki, Toshio Iijima, Hiroshi Fujino | PROFILE DRAG OF CIRCULAR CYLINDERS WITH SURFACE ROUGHNESS OF RECTANGULAR GROOVES IN LONGITUDINAL DIRECTION | profile drag- circular cylinder- drag coefficient- surface roughness- rectangular groove- Reynolds number | The profile drag of circular cylinders with rectangular grooves along the longitudinal axis on cylindrical surface and a smooth circular cylinder was measured in range of Reynolds number Re =10000 - 7.1 x 10000 in a uniform flow. The influence on drag coefficient of groove roughness was studied experimentally. The measurements of profile drag were carried out by a direct method using the strain gauge type load cell and the indirect method applying the momentum equation by B.M. Jones. As the groove roughness increases, the turbulent boundary layer was formed at lower Re and drag coefficient CD for rough cylinders decreases abruptly in the range of lower Re. Values of CD for the rougher cylinder begin to decrease abruptly when the value of roughness Reynolds number becomes approximately 350. As the measuring position moves at closer range to the cylinder, the error of CD obtained by Jones' method is occurred by violent separation and vortices behind the cylinder. |
| 288 | F.C. Tang, B.H.K. Lee, L.Y. Jiang and Capt. R. Lafrance | SURFACE PRESSURE MEASUREMENTS ON AN AIRCRAFT WING USING THE PRESSURE SENSITIVE PAINT TECHNIQUE | pressure sensitive paint, wind tunnel measurement, transonic flow | Surface pressure measurements on a 6% scale model of the CF-18 have been carried out at the Institute for Aerospace Research 1.5m X 1.5m Trisonic Blowdown Wind Tunnel using pressure sensitive paint technique. In this investigation, pressure data on both the upper and lower wing surfaces were obtained. The test was performed at a mean chord Reynolds number of 4X106 and at Mach numbers ranging from 0.6 to 0.95. The angle-of-attack of the model was set at 0E and 4E respectively with leading and trailing edge flap angles at 0E. Detailed quantitative pressure distributions on the model wing surfaces were obtained. Accuracy of the measurements was assessed and discussed. The images obtained using the pressure sensitive paint technique also served as a very indicative flow visualization tool. |
| 289 | Chinda Charoenphonphanich, Tawatchai Nakapipat, Hiroshi Niwa, Hisayuki Ennoji,Toshio Iijima | VISUALIZATION OF FLOW AND MIXING OF GAS IN CYLINDER OF A STRATIFIED CHARGE ENGINE WITH TWO INTAKE VALVES | internal combustion engine, stratified charge, flow, mixing, turbulence | A numerical analysis of the flow and mixing of rich mixture and air which are inducted into the cylinder through each of the two intake ports of a new type of stratified charge spark ignition engine with two intake valves have been carried out by finite volume method. In order to confirm a validity of the numerical analysis calculation results are compared with experimental results obtained by using an optical engine and particle image taken by a high speed camera. Flow velocity and flow pattern, distribution of turbulence, and distribution of mixture concentration in the cylinder during intake and compression strokes at engine speed from 1000 to3000 rpm are visualized. Flow and mixing phenomena of the mixtures in the cylinder and effects of the engine velocity on the characteristics of flow and mixing in the engine cylinder are made clear. |
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AT.Uemura, N.Yonehara, T.Toshiyasu, and M.Yamauchi | FAST AND HIGH PRECISION ANALYSIS METHOD FOR PIV | piv, ptv, fast algorithm, sub-pixel precision.. | In this paper, some methods are examined for improvement of measuring precision of the successive abandonment algorithm, which consists of the SSDA and the F-test technique. It is also important to suppress calculation time within a minimum increase. Four sub-pixel precision estimation methods, which are a weighted mean, bilinear fitting, image shifting, and a quadratic curve fitting, are examined. When the quadratic approximation is combined with a coarse search, the measuring precision of about 0.02 pixel is achieved without significant increase in analysis time. |
| 291 | Makoto Tsubokura, Toshio Kobayashi, Nobuyuki Taniguchi | VISUALIZATION OF 3-D STRUCTURES AT A STAGNATION REGION OF A PLANE IMPINGING JET USING LARGE EDDY SIMULATION | numerical flow visualization , large eddy simulation, plane impinging jet, turbulent coherent structure | Numerical investigation of a turbulent plane impinging jet at Re=6,000 normalized by the inlet velocity and the nozzle width was conducted using Large Eddy Simulation(LES) technique. LES is suitable to capture three dimensional structures of turbulent flows because it simulates 3-D larger eddy structures instantaneously so as to model only smaller scales of more isotropic eddies. We used the improved subgrid-scale(SGS) model to simulate properly transition of turbulence observed near the nozzle and complicated structures of turbulence observed near the stagnation region. The predicted statistics such as mean velocities and turbulent intensities showed good agreement with the experimental data obtained by the Laser Doppler Velocimeter (LDV) which clearly indicates the validity of our method. Some organized structures of the flow field were extracted from the computed instantaneous spatial distributions of velocity and pressure field. Simulated flow fields were also animated using the snapshots of the instantaneous flow field. We could observe both in still pictures and animation some turbulent structures of stretched eddies at the stagnation region of the impinging jet which have already been structure is considered to be the typical organized eddies that works to increase heat and mass conductivity at the stagnation region We can say that our LES simulated the flow field well to show its validity for the three dimensional analysis of turbulence. |
| 292 | Aaron Drake Robert A. Kennelly, Jr. | OIL FILM INTERFEROMETRY FOR SKIN FRICTION MEASUREMENT ON AN AIRCRAFT IN FLIGHT | trip disks; boundary layer; skin friction; oil film interferometry; flight testing | Measurement of skin friction on an aircraft in flight is difficult. Most methods that have been used, such as Preston tubes or floating element balances, require extensive plumbing or modifications to the aircraft surface. Additionally, they only provide data at a single location. As a result, boundary layer measurements are rarely made in flight testing. A method of skin friction measurement which requires no modification of the aircraft is oil film interferometry. Developed in the 1970s, oil film interferometry has seen increasing use in wind tunnel tests as a direct skin friction measurement technique. This paper presents the first results of this quantitative flow visualization method on an aircraft in flight and discusses the challenges encountered in the application of this technique to flight testing. |
| 293 | Gvozdeva L.G., Lagutov Y.P., Sharov Y.L. and Scherbak N.B. | VISUALIZATION OF THE FORMATION AND PROPAGATION OF SHOCK WAVES IN A POROUS COMPRESSIBLE MEDIA | visualization, shock and detonation waves, interaction with porous compressible materials, residual deformation | A new optical method is described which is based on the simultaneous visualization of density disturbances in reflected and in transmitted light. In reflected light a system of lines is recorded which has been drawn on the surface of a porous compressible material. This picture gives the distribution of density inside the material. In transmitted light the process in the gas phase is recorded with schlieren optics. Simultaneously taken streak records in reflected and transmitted light give a complete picture of the wave pattern, its development in time, and the distribution of density in the material. The paper presents results obtained using this method to observe the behaviour of a compressible porous material under the impingement of shock waves. It has been found that the explanation of this phenomenon lies in the dynamic character of the process. Characteristic features of formation and structure of the compression wave inside the foam are revealed. The influence of percolation is stated. A new form of residual deformation of porous material has been established. |