The stratified flow around a hemispheric obstacle on a flat plate has heen studied. The flows were produced by towing an inverted body through saline-water solutions with stable density gradients and were visualized by dye-injection method. The study demonstrated that three types of the flow structures were formed depending on the stratification. Two types of them are similar to the neutral cases but are strogly affected by the three-dimensional lee wave. In case of strongly stratified flow, most of the fluid cannot surpasses the hemisphere but passes around it and forms Karman vortex street behind the hemisphere. The change of the flow structure is closely related to the K-H instability in front of and behind a hemisphere.

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The coherent structure of meandering flow is investigated using two flow visualization techniques which are plan and streamwise view by fluorescent dye injection method.
The result indicates that dye transport pattern, which phase shifted by a half period of meandering channel phase, is formed near the wall and depends on the changes of Reynolds number. Further the result suggests that large-scale vortex is formed on the convex side wall. It seems that these are typical coherent structures of turbulent meandering flow.

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Organized structure formed on Uroco-roughness bed in turbulent channel flow is investigated using two flow visualization techniqes which are a fluorescent dye injection method and a aluminium dust method. The result indicates that a staircase structure of wall streamwise vortex and a oscillation of the structure play a important role to form parallel spiral flow on Uroko-roughness bed in turbulent channel flow.

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Natural and Forced convection of molten silicon during Czochralski single crystal growth was directly observed using X-ray radiography and solid tracer method. The tracer, whose density and wettability were adjusted to that of molten silicon, was newly developed. Observed flow of natural convection of molten silicon in a crucible was not only steady but also transient, and not axisymmetric but asymmetric.

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In the present paper a visualization experiment by 'Phenole Phthallein method' is applied for the juncture flows around a cylinder mounted on the bottom of towing tank. One of the important observations is the periodic motions of the locations of foci or the length of twin vortices behind the cylider. The experimental pictures are compared with the solutions for three dimensional full Navier-Stokes equation shown for the internal flows flows such that around the cylinder between two parrael flat plates.

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Visualization of two-phase flow were carried out by using a neutron radiography method, which is suited to visualize gas-water two-phase flow in a metalic tube. Nitrogen gas-water two-phase flow in a stainless steel tube and water boiling two-phase flow with and without a twist tape in a stainless steel tube were visualized.

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In this study, an image processing system was developed to measure velocity vector distributions in a three-dimensional flow field. The procedure is as follows. 1) A color tracer image is obtained by using color slit method. 2) The image is separated into two tracer images by color separation. 3) The velocity vector distributious in two different depths of a three-dimensional flow field are simultaneously obtained by correlation method.

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The motion of tracer particles in liquid flow is disscussed by the stability theorem of the macroscopic concept.
When the volume fraction of the tracer particles in liquid flow is small, the neutral or stable stability condition can be expected in the motion of tracer particles in flow.

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The purpose of this study is to clarify the motion for fluid-suspended particle. Experiments are tried in two dimensional open curved channel made as one simple half-circle model for an eddy flow model. As a result, trajectories of suspended particle for various particle diameters and densities become clear.

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An indivisual coherent structure in a wind induced turbulent shear flow of water was investigated by using flow visualization technique and a Beam-Scanning-type LDV (SLV) which can measure pseudo-simultaneous velocity profile in a cross section. The visualization of the structure by applying conditional sampling technique indicated an appearance of the structure. But the numerical simulation with a vorton model showed a defect in the visualization technique. So by using SLV the structures were measured. The results of the investigation suggest that the condition to sample the structures is proper and that the quantitative results obtained before show the right features of the coherent structures.

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The speckle photography has been established as a method of velocity measurement in two-dimensional flow field at the same instance. This method is based on taking a double exposure photograph (specklegram) of measuring field, seeded with tracer particles and illuminated by pulsed light sheets. If a pulsed light source combined a low-power CW-laser with a beam chopper is used for this method, the intensity of light sheet is not sufficient to obtain a fine specklegram of the flow suspending with small tracer particles following up the flow.
In this report, a new technique that the flow field is swept by a laser beam generated from a He-Ne laser source (15mW) is developed and named as the beam sweep laser speckle velocimetry. This method is applied to velocity measurement of a flow with a horseshoe vortex produced by a triangular column placed into a laminar boundary layer developed in a water channel flow suspending TiO2 particles (mean dia. 5μm). As the result, the fine specklegram is obtained for quantitative flow visualization.

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Flow and temperature fields of natural convection in hemispheres heated from below were visualized by using thermo-sensitive liquid crystal powder. The ranges of Rayleigh and Prandtl numbers of the present experiment were 1×10 ⁵<Ra<1×10 ⁹ and 6<Pr<10000, respectively. Steady circulating flow was observed at about Ra=1.9×10 ⁵. The thermal boundary layer on the hot surface began to separate about Ra>2×10⁵ and the number of separation points increased with increased in Rayleigh number. The position of the separation points was fixed and the flow was generally periodic for Ra<10 ⁸. Above Ra=4×10 ⁸, regular separation could not be observed. The results indicate that the transition from laminar to turbulent may be completed at fairly high Rayleigh number.

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An image processing measurement system was developed to obtain simultaneously both the velocity and temperature distributions from the images of dynamic behavior of the thermal stratification, visualized by using liquid crystal tracers. The correlation method was used to obtain the velocity vector distributions. In addition, an algorism for color discrimination using RGB notation system was applied to the color images to obtain the temperature distributions. Consequently, the efficiency of this system was confirmed.

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Isotherms of the natural convection in a square cavity have been obtained via an image processing which captured by means of the liquid crystal capsule method. Also provided have been the results of the flow pattern plotted by pearl pigment particles. The results of isotherms and flow patterns have been compared with the solution for the same prameter with a simple Boussinesq approximation. The purpose of the present paper have been to comfirm the thermal field visualization by the liquid crystal capsule method and to provide a guideline in developing a new computer program code for such a flow field experimented.

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Vortex dynamics behind a circular cylinder with a splitter plate in the wake was investigated by the discrete vortex model. The splitter plate was modeled by a series of source which could cancel out the flow across the sources.
The calculation shows that the position of rolling up of elemental vorticies is controlled by both the length of the plate and the gap between the cylinder and the plate. The position is strongly related with the surface flow of the cylinder near the down stream stagnation point.

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Bridging phenomenon in crosslinking two vortex rings has been studied. Phase locked measurements of velocity using X-type hot wire were carried out over the whole flow field trasversing point by point, and time dependent vorticity fields were educed. Creation of new pair of vortex tubes was found in the interacting rtex rings.

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Three-dimensional laminar flows in various curved pipes(i.e., Rc/a=2, 4, 7 and 9 for curved 180 degree pipes and Rc/a=2 and 4 for curved 90 degree pipes) were numerically simulated by using time-dependent incompressible Navier-Stokes equations. The boundary-fitted coordinate system was used in order to treat the complicated boundary configurations of strongly curved pipes. The obtained flow patterns and the magnitude of the secondary flow in case of Rc/a=9 for curved 180 degree pipe were in good agreement with the experimental results. The ellipticity of the basic equation was very important to simulate these recirculating flows, especially when the curvature ratio was small. Velocity and pressure fields were visualized by a pseudo-color technique on a workstation.

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The flowfield of a ship's propulsion mechanism consisting of two-series wings in a square channel are visualized by numerical simulations using a personal computer and by the hydrogen-bubble technique. The simulations are performed by the discrete vortex method, in which the separations are assumed to occur at the trailing edges of the wings. The stream-lines, the streak-lines, and the time-lines are calculated, the latter two of which are obtained by introducing the tracers at adequate intervals. They agree well with experimental results. The flowfield is unsteady and complex, but the characteristics of the flow are clarified by visualizing numerically.

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To understand the combustion process in a spark ignition engine with an unscavenged horizontal prechamber, the flame propagation in both the pre- and main chamber is simultaneously visualized by a high speed camera changing the torch nozzle area, while keeping the engine speed of N≅1000rpm, the volumetric efficiency of ηv≅80% and the air-fuel ratio of A/F≅15 constant. Then an image-processing camera is used to assign the brightness of flame photograph into 16 steps of false color, and the signals of brightness are stored in floppy disk of computer through an image memory (or slot card). Such image-processed flame patterns are projected on the T.V. display and possible to be taken photograph by a still- or 8mm camera.
Accordingly, it is seen that the patterns of flame propagation in the main chamber are remarkably affected by torch nozzle area and the ratio of burned portion to main chamber area (combustion area fraction) is also similar to the engine output (BMEP). Furthermore the time history of averaged brightness distribution on the center line of the main chamber is found to be in reasonable agreement with the time history of combustion gas temperature on the same line measured by an infrared pyrometer.

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Motion graphics of flow around an automobile were made. Unsteady flow field was calculated by the finite difference method using third order upwind schemes. Motion graphic systemwas composed of mini super computer and graphic work stations. Unsteady flow motion in the wake was made clear by movies. It is concluded that the motion graphic system is very useful to understand the unsteady flow.

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The flow pattern and velocity distribution of coolant flow around cylinder liner of diesel engine are studied by numerical calculation and experiental observation in this paper.
The calculation is performed with the 3-dimensional model by finite element method for fluid flow. The result of flow calculation is visualized by velocity vectors. And this result is compared with the experiment by oil film method. Both calculated and experimented results give good agreement in flow pattern.
The 3-dimensional calculation of coolant flow by finite element method is effective and practical for analizing the coolant flow problems in engines.

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This paper shows computer-aided air flow visualization(CAFV) of exhaust air from outdoor unit of air-conditioners which are installed on every floor of a multistory building. After generating the complicated orthogonal meshs with automated fluid/solid cell determination thermo-fluid flow analysis is carried out with the Finite Volume Method Solver specially turned for air-conditioner simulation. Then, the results obtained are visualized through a highly interactive 3-D graphic display. Three dimensional colored contours and color fringes of temperature distributions visualize the convection flow along the building surface which is induced by the hot exhaust air from the outdoor units. Three dimensional vector display also help us understand the complicated flow structure around the outdoor units.

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The effect of subcooling on nucleate pool boiling heat transfer was studied on a horizontal platinum wire, 0.1mm in diameter and 50mm in length, using Freon R113 at atmospheric pressure. Rate of subcooling was changed from 1.7 to 37K. A high speed VTR (400 frames/s) was used to visualize boiling characteristics. On higher degrees of subcooling a higher heating surface temperature was measured in a developed nucleate boiling region where data were correlated by q=C.ΔTs⁷. The images of the VTR were processed to examine frequency of bubble departure and bubble size.

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An experimental study has been performed to investigate the breakup of the droplets by using shock tube in the range of Weber number of 55 to 1500. Breakup process is observed by means of shadowgraph method. Experimental results show that the break-up process could be devided according to their characteristics into two processes, which are the initial deformation process and the disintegration one. The type of initial deformation is unchanged over the range of present Weher number.

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Water tank experiments were conducted to investigate plume rise and diffusion of gases discharged from stacks under calm conditions with field wind velocity less than 0.4m/s with stable thermal stratification.
The plume rise phenomenon was illuminated LASER light sheet, and recorded video camera. The brightness of an image was transformed into concentration of a tracer liquid, by the equipment of digital image analysis.
Plume rise height and plume lengths were measured from the concentration distribution of plume.

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The purpose of this study is to clarity most suitable ventilation method in tunnelling around the face. The models of a tunnel used were a 1/20 scale model for air experiment and a 1/100 scale model for water experiment. Flow patterns for both models were studied by flow visualization techniques. Velocity distribution of 1/20 scale model was measured.
First of all, the wind direction and velocity in an actual tunnel and a 1/20 scale tunnel model were measured. Then, the similarity flow was confirmed between the tunnel and the scale model. The tracer method was applied for the two-dimensional flow visualization by using Laser light sheet(LLS), and the tuft grit method was applied for three-dimensional flow visualization.
According to these results, it became clear that the most suitable ventilation method in tunnelling around the face was the air pumping type setting the duct at side position.

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To utilize heat energy stored in solar ponds, it is common to extract hot water from the storage layer and return it after the heat-exchange to the same layer. But the injection of the cold water causes a complex flow in the storage layer especially when the pond is heated by the sunshine at the same time.
The purpose of this study is to get basic knowledge for the behavior of flow in solar ponds under heat extracting condition. For this purpose, an experimental pond was built and flow in the pond was ovserved using flow visualization technique including a Laser Light Sheet method. Thermometry over the flow field was also done.

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Turbulent flow in a pipe is visualized by the hydrogen-bubble method. Bubbles are generated continuously from a platinum wire seting along the diameter of the pipe. The bubble-curtain is observed from the side and the downstream. The behaviors were recorded on video tapes, and were analized by an image processing system.
The deviations in x-direction from the original location show the maximum around Y/R=0.3 (y ⁺?? 40).

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A circular jet in a coflowing stream is computed using a supercomputer by axisymmentric discrete vortex method, and results of analysis are visualized by a computer movie system using a personal computer and a magnetic tape device. This system programed with a C-compiler enables fast drawing on CRT, and therefore the evolution of vortex pattern is visualized as a movie without the conventional frame-by-frame recording technique. The formation of large-scale clusters of vortex rings and their amalgamation with neighbouring clusters are clearly observed by color marking on particular vortices in the movie. These motions are very similar to the flow visualization experiments.

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The object of the present study is to establish a new method for the automatic measurement of unsteady slow flow field with vortices, using a digital image processing system. The flow patterns of viscous diffusing free doublet are recorded on VTR. The two pictures of visualized flow at small time intevals Δt are stored in an image acquisition board. After bi-level quantitation, each image of objective tracer between the two pictures is identified by a new coorelation method. The velocity vectors and vorticity contour curves are dipicted, and the flow mechanism of doublet is explained like that the fluid arround a doublet convected with otherwise uniform flow is rolled and engulfed in it and that it diffuses gradually.

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Two dimensional velocity distributions at an open-channel confluence were obtained by applying the image processing technique. In this study, the so-called correlation technique was used to analyze visualized flow patterns at the water surface. The correlation technique was improved by considering small rotations of the reference frame to be applicable to the vortical flow field. The improved method gave good results especially in the region of separated shear layer at the confluence. Also, the accuracy of this technique was examined in detail.

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At the fundmental study on the three dimensional turbulent structures, visualization technique by particle tracer methods were used.
Experiment have done in the rectanguler open channel for a small aspect ratio (B/H=0.5). In oder to visualise scondary flow patern and terbulent structures from inner region to outer region, particle tracer methods and vertical ( or horizontal ) light sheet methods were used.
In this paper relation between the mechanism of wall turbulence and the mechanisms of secondary flows are discribed in detaile.

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A new technique has been developed whereby 2-D velocity distribution in a fluid flow is measured automatically within a very short time. The technique is realized on a simple 16bit personal computer system by a high speed algorithm of calculating cross-correlation between two pictures, and new methods of removing erroneous vectors.
For the typical analysis time including the influences of such factors as numbers of tracers and dimensions of correlation area, the values fall around 10-20 seconds to obtain 100 vectors from a couple of 200x240 bi-levelyzed pictures.
Some examples of the measurement such as a rotation of a turn table, and a natural convection flow in a tank are shown.

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A technique for measuring an instantaneous distribution of three velocity components in a turbulent water flow was developed using a digital image processing system. This system, which consists of three TV cameras, a digital image processor, a laser disk recorder and a stroboscope, can measure fluid velocities by tracking three-dimensional motions of fine particles suspended in the flow field. The motions of the particles are observed by the TV cameras simultaneously, and then the image data are stored on the laser disk recorder. From consecutive image data obtained at a 0.1s interval, three-dimensional displacement of each particle is calculated based on stereoscopic photogrammetry. Both data aquisition and reduction are carried out automatically by the image processor interfaced with the microcomputer. Measurement uncertainties associated with the technique are systematically evaluated. Traceability of the particle, pathline averaging effect and spurious vectors arising from mistracking of particles are examined carefully. The decay of turbulence generated in a stirred water tank is measured to test applicability of the technique to turbulent flows without mean flow and strain rate. Present results show a good agreement with a prediction obtained by a turbulence model.

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A new technique for measuring three-dimensional velocity components is applied to an axisymmetric turbulent jet. Fine particles suspended in the flow field are tracked successively in time. Instantaneous three velocity components are calculated on the basis of stereo photogrammetry by a digital image processing system. The measurement uncertainties associated with the technique are evaluated and the applicability to shear flow turbulence is examined. The measurement uncertainty depends mainly upon the resolution of the digital image processing system and is nearly equal to ± one pixel at 20:1 odds. Turbulence in the self-preserving region of the axisymmetric free jet is measured and some of its statistics are calculated. Those obtained include the mean velocities, the three rms fluctuations, skewness and flatness fac-tors, and the Reynolds shear stress. The longitudinal velocity fluctuation is somewhat larger than those obtained by the previous measurements with hot-wire anemometries, while the others fall within the range of the available experimental data.

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This paper describes the technique of three-dimensional graphic display for the shock wave structures. The shock waves generated at a "U" shaped pin which is moving in the supersonic flow field of a converging-diverging nozzle is visualized by the double pulsed holographic interferometry. The hologram obtained by this method is reconstructed and the shock wave profiles at each of the cross-sections of the real image are thinned by image processing. The numerical data which indicated the thinned shock waves are constructed by computer graphics techniques. As a result, the three-dimensional shock wave structures were clearly visualized by graphic display.

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The verocity distribution is measured by the following ways. The air flow surrounding an obstacle set up in the uniform flow is visualized by smoke. It is recorded by VTR. An area is corres-ponded with the area that is similar in the gray level distribution in continuous frame.
The method of correspondence, using this paper, is the search for the points which have the minimum value of gray level difference. This is named gray level difference method. This method is compared with the existent correlation method in efficiency. By eliminating the areas which have the flat gray level distributions from the ob-ject of the search, the number of wrong correspondence is decreased. Its effects are examined.

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Some methods to identify tracer particles in different images in a measurement of velocity distribution through analyzing visualized flow images are compared. Performances of the methods, judging from the distance between particles, the logical product between images and the linearity of tracer's motion, for Poisuille flow or Karman voltex street are simulated, and the applicable range of each method is discussed.

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The purpose of this paper is to devise a high-speed image analysis algorithms. When the velocity vectors are derived from the pictures with a small time-difference, the one-to-one correspondence of tracer images must be found among the pictures. In this paper, a unique idea is presented for the automatic tracer tracking and the identification of tracer images.

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An infrared radiometer has been used for detecting and visualizing surface cracks and scratches of metal and graphite. The image of surface flaw can be displayed on the CRT under a remote sensing condition by using the infrared radiometer. Two dimensional distribution of radiation energy emitted from the cracks shows an isothermal line image on the CRT by radiation cavity effect. The width and depth of surface cracks can be measured with increase in the radiation temperature.

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Maneuvering stability of a passenger car is threatened when it is subjected to intensive oblique wind.
In this study the flow around an automobile body in the oblique wind was carried out by numerical calculation with vortex lattice method. Visualization by the experiment with oil film method and tuft grid on a 1/8 scale model was also carried out to compare with the results of calculation. Good coincidence was obtained between the experimental results and the calculation.

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Measurements have been made on simultaneous fluctuating surface pressure distribution of 3-dimensional bluff bodies. We carried out wind tunnel experiments using various models with different aspect ratio(1:1:1, 1:1:3, 1:1:5 ; cubic cross section). Measuring system has 512 point pressure transducers(16 channel per 1 module which has electrically scanned multiplexer and preamplifier) and 32 channel analog to digital converters. Observation has been made on 16mm movies created by mean of computer graphics. It was found that various pressure distribution patern can be observed using this new system.

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The Short Take Off and Landing research aircraft "ASUKA" adopts an Upper Surface Blowing scheme as a powered lift system. Thus, exit flows from four engines mounted above the main wing are expected to attach well to the surface of wing and its downstream flaps in order to produce additional lift force. The report concerns flow visualization results from single engine outdoor tests and ASUKA ground tests. Introduced FV techniques are wall temperature non-contacting measurements with an infrared camera and water injection into engine exit flow.

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An analysis of electric fields in dielectrics plays a very important role to design an insulation capacity of electrical machineries and to clarify a mechanism of dielectric breakdown. Especially, it is expected that the direct observation of continuously changing electric fields of them give tremendous contributions to insulation design. The anthers have been studied to analyze and simulate some types of electric fields by a fluid flow mapper which is an equipment of fluid flow visualization. This paper visualizes and analyzes electric fields on spherical shape voids occurred within dielectrics put into a parallel plate electrodes by means of the fluid flow mapper method. Finally, the graphical results from flow patterns of the complex dielectic system are compared and examined to appreciate the justification of this method applying to this system by the analytical and the numerical results of it's electric fields.

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The present paper discribes the results of the flow observation around a discus-type navigation buoy which is used in fairly strong tidal currents, The so-called milk-painting method was used for the flow visualization of limiting stream-line and separated vortex flow. Several three-dimensional separations are occured on the bottom and the side wall of the buoy, The starting vortex and wake genarating process in low speed flow are also observed by using the milk-painting method with laser light sheet.

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Gap flows between parallel rotating disks are visualized by using a waterflow with polystirene particles modeling technique for a airflow. The experimental parameters are revolution fo rotating disks, chape of centrally clamped disk pack axis (with or without flow from axis), and with or without a shroud. The experiment shows flow patterns and local velocities of flow for several conditions.

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A butterfly flies with beating a pair of wings. In order to estimate the aerodynamic forces acting on the wings, the heating motion of the wings was simulated by the flapping motion of a triangular plate and its mirror image, caused by free falling of the plate about a flapping hinge in water tank, and was analyzed by observing the plate motion filmed with a still camera and a cine-camera. By painting the plate with a soluble dye the vortices generated at leading edges and vortices shed at trailing edge of the plate were visualized during the flapping motion. The configuration and position of these vortices were utilized to analyze the induced velocity on the plate.

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A number of starting flows past a fixed or pitching airfoil at large incidences are investigated by means of experimental and numerical visualizations. The study is concerned with two-dimensional incompressible cases in which the flow is initiated by an impulsive motion around an elliptic airfoil at chordal Reynolds numbers smaller than 10 ⁴. The main object of the research is to reveal phenomenologically some marked characteristics of the unsteady airfoils in the so-called deep stall regime in comparison with those in the light regime. Another definite purpose is to examine, in some detail, the respective and combined effects of the major experimental parameters on the vortex formation and wake development around the airfoil. It will be shown that the wakes of the fixed airfoil at large incidences bear some analogy to those of a flat plate at incidence.

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Flow visualization of flow field around a winged space vehicle has been conducted. Flow visualization techniques using color oil and smoke are used. Interacting flow between body and wing and separation lines and reattachment lines on the body surface are visualized by oil flow technique. Also vortical flow field around body is visualized by smoke method. Adding to those experiments measurements of aerodynamic characteristics of winged space vehicle are conducted. The results from flow visualization show same tendency of aerodynamic characteristics of the body.

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