| 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 |