An axisymmetric air jet impinging obliquely on a flat wall is visualized by using the oil film method. As a result, a small point of oil film is found to remain in the flow pattern on the wall and proved clearly to be an origin of flow near the wall (O*) by the tuft-stick method. Further, this point is obviously different from the geometrical intersection (O') and the stagnation point (O). In the paper, effects of jet velocity, impinging angle and impinging height on both the distances (λ or δ) between O and O' or O and O* are investigated by using the oil film method.

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It goes without saying that direct observation of flow is indispensable to study detaily the groundwater movement in rock mass. The authors tried to observe the transient and unstable behavior of thermally induced groundwater flow above a heat source in idealized model of fractured rock mass by the use of thermosensitive liquid crystal films (TLCF). Experiments were performed in a soil box surrounded by insulating plates. Heat was electrically. supplied from bottom of the box by means of rubber heater plates. The fractured rock mass was simulated by filling three types of glass beads in the box. As the conclusion it was found that unstable flow such as plume was generally formed above the heat source in high permeable part in the experimental model representing fault zone.

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Some important flow patterns in astatically stable fresh-salt water system were visualized using simple dye methods. Dye streak from a point source set up above interface of the flow system indicated a spiral pattern for high shear flow. This pattern means there occur coherent vortices caused by the internal shear instability. Visual observation shows that this instability effect extends to interface and constrains interfacial waves to generate. Line source by a dyed thread made it possible to visualize the three-dimensional stream structures in each layer and to obtain velocity profile from its time lines. Dyed thread mesh was successful in the observation of longitudinal vortices which play a very inportant role in the cause of the internal shear instability. Of all these visualizations Uranin was found the most. useful as dye material.

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It is desired that researches on the fluid dynamics of swimming to rise record of swimming match, but there are only a few investigations and these are not sufficient to solve fluid dynamic problems on swimming. The purpose of our research is to make clear the state of flow around the human body at swimming and to get the data to improve the swimming form. In addition, it is thought that there is the possibility of rising swimming record by the improvement of design and material of swimming suits.
At first step, we carried out the flow observation on a rigid model of human body, in the circulating water channel at naked condition by oil film method and with swimming suits by surface tufts.
As results, the water flow around the rigid model of human body were made clear at towing condition of constant form.

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The flow pattern around a rectangular cylinder were observed by the visualization used tracer technique and by L.D.V. in the uniform flow of Reynolds number lower than 10 ³. Two different Strouhal numbers were found in the wake of the rectangular cylinder having width-to-height ratio of 5-8 at Re=890. Lower Strouhal number was caused by the vortex shedding from the side wall of the cylinder and higher one from trailing edges. The vortex shdding from the side wall seems to be the result of fluctuation of the shear layer separated from the leading edge. This vortex shdding from the side wall affected in the flow pattern of the wake at Re=890, but the influence of this vortex in the wake were weaker in the range of smaller Reynolds number.

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The flow around a semi-infinite circular cylinder placed at various specings to a flat plate has been investigated experimentally. The cylinder was aligned with its axis normal to the flat plate and to the free stream. Then, the pressure distributions along the plate were measured and the flow patterns were visualized using the oil-film-technique at a Reynolds number of 2.9×10 ⁴.While, the flow around the cylinder was visualized using the liquid-parafine-mist-technique at a Reynolds number of 330. When the gap was small, three flow patterns occurred around the cylinder : horseshoe-like vortex, symmetrical vortex and Karman vortex, and one or two separation points along the plate were observed too.

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The three-dimensional structure of the flow in the wavy channels was visualized using the hydrogen bubble technique in the laminar and turbulent flow regimes. In the laminar range, a two-dimensional stable recirculation vortex occurred in the valleys of wavy walls of the channel. In the transitional range, the separated shear layer between the main flow and the recirculation vortex rolled up into a transverse vortex due to the amplification of small disturbances. The transverse vortex came under the influence of the shear layer reattachment as it was transported in the flow direction and impinged on the wavy wall. That was, the stretching of the transverse vortex produced a streamwise (longitudinal) vorticity. In the turbulent range, the three-dimensionality extended a whole region in the channel. This would be due to downstream convection of nonuniformities through the main flow and upstream convection of nonuniformities through the recirculation vortex.

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This paper presents flow patterns of coaxial impingement of opposing jets, which are modeled on the jets in the mixing chamber of reaction injection molding. The flow visualization is carried out by the hydrogen bubble method by using water as working fluid for the jet Reynolds number from 50 to 1700.
The results show that the flow patterns of the impingement are approximately classified according to the Reynolds numbers as follows.
(1) Re ?? 200 : The flow is stable, as the flow downstream of the impingement surface has no obvious fluctuation.
(2) 200 ?? Re ?? 500 : The impingement surface is unstable, as it may be traveled by a trivial disturbance.
(3) Re ?? 500 : The flows upstream and downstream of the impingement surface have some fluctuation, though the impingement surface is almost fixed.

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This paper is study on mixing process of two-dimensional confined jet. Confined jet flow is very important for combustion chamber, jet pump, fluidic device, etc.
In this study, flow pattern of mixing chamber has been investigated by using flow visualization technics.
As a result, it has made clear the separation point, reattachment point and separation region for effect of Reynolds number and velocity ratio.

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Instantaneous velocity fields over model rippels were obtained from records of hydrogen bubbles on films shot every 0.1 sec for 20 sec.
Temporal and spatial diatributions of coherencies of velocity fluctuations were analysed and it was found that at the ripple crest, higher coherency values were confined to the regime of lower fluctuation frequencies. However, at the section near the re-attachment point, higher coherencies were distributed more widely. Power spectra of velocity area fluctuations in a sublayer of about 2 cm deep from the bottom were calculated, these showed clearly an increase of organized turbulent energy near the re-attachment point. The spectrum peek was near 2 Hz which coincided with that of vortex shedding from a cylinder of comparable diameter.

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Deformation and movement of a vortex in the decaying stage were investigated by measuring velocity fields around the vortex with tiny polystyrene particles dispersed in the fluid layer. The vortex was produced in a rotating water layer by withdrawing a fixed amount of water through a small hole at the top boundary. When the vortex was produced in a fluid layer at rest relative to the rotating tank, it spined down keeping the circular shape. When the vortex was produced in a parallel flow with a horizontal shear whose vorticity has the same sign of that of the vortex, the shape of the vortex was elongated in the direction of the parallel flow. When the sign of the vorticity of the shear flow is opposite with that of the vortex, however, the vortex was elongated in the normal direction to the shear flow and moved toward the center of the container at the same time. It was found that the essential dynamics of these phenomena can be explained by linear superposition of the forced vortex with the parallel flow with a horizontal shear.

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The visualization of a flow pattern trantions has been carried out in an annulus with a concentric rotating inner cylinder. In order to visualize, the water with aluminum powder was used. Varying the Reynolds and Taylor number, flow pattern trantions of laminar to turbulence flow and of secondary flow was observed.

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We visualized the flow on the ripple model by the tracer injection method. As the result of it, we obtained statistical regulations for the rength of reattachment point and the scale of eddy on the wake area as for irregular flow of the ripple models.
In this repot, the period of the vortex shedding and the vortex velocity in wake behind a crest of the ripple model were obtained by flow visualization. These results were contrast in a striking way with the Karman vortex street behind a circular cylinder.

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A practical flow visualization is applied to blood flows through blood vessels to fully understand the macro- and microcirculatory pathophysiology. A model study was made using the fluid-dynamical similarity in order to examine the detailed structure of blood flow in a cerebrovascular aneurysm. The steady and pulsatile flows were visualized in a curved model vessel with an asymmetric aneurysm using a tracer method. A laser Doppler velocimetry was also used to measure the pulsatile velocity in aneurysm.
It was observed that vortices were induced in aneurysm, influencing the flow structure and velocity at the presence of the secondary flow due to the vessel curvature. It was suggested that blood flow in cerebral aneurysm may be influenced by the secondary flow as well as the pulsation.

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The integral-average heat transfer coefficient of 2-D impinging jet has been augmented as much as 60% on the wall with large-scale wavy roughness. The mechanism of this heat transfer augmentation is studied with emphasis on two primary flow structures in the impinging flow region by using either the surface floating method or the smoke-wire technique. They are the streamwise vortex-like structure, which is characteristic to the impinging jet, and the spanwise vortices associated with the flow separation around the roughness. The combined effect of these structures can effectively augment the heat transfer particularly in the downstream region where the heat transfer usually deteriorates considerably.

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In the previous papers, we measured pressure distributions, lift and drag forces and Strouhal numbers of two rectangular cylinders arranged side-by-side in a wind tunnels. Then, we observed flow-patterns around two cylinders by the aid of the visualization technique of a smoke-wire, changing the shape of a cross-section of models (B/H) and a gap distance (S/H) between two models. It can be clarified that a change of flow-patterns corresponds to one of aerodynamic forces measured. It was found that there occurs a biassed flow under the critical gap distance, and that bi-stable flow-patterns of the biassed and the non-biassed flows alternately appear just at the critical gap distance.

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The characteristics of the structure of the streamwise vortice in the near-wall region are investigated. The streamwise vortices make a pair in the buffer layer and log-region. The pair of the vortices counterrotates each other and lift up more low speed fluid near the wall in between the vortices taking with a separation from the wall surface. The pair of vortices, which is termed "mushroom vortice", generates in the buffer layer and develops inclining to the flow direction.

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Coherent fluid motions near the wall in a two-dimensional turbulent channel flow have been visualized by using a sophisticated hydrogen-bubble technique with partially insulated fine tungsten wires, which generate segmental hydrogen-bubbles, at several distances from the wall. The motions of the segments of bubbles are illuminated in the thin frame perpendicular to the flow direction and are recorded in 16mm motion pictures. These flow visualizations supply not only a direct evidence for the existence of streamwise pseudo-vortical motions but quantitative data of fluid motions in the wall region. Further data reduction with a micro-computer produces instantaneous distributions of two velocity components of v and w as well as streamwise vorticity of w _x in the y-z plane, which are extremely difficult to obtain by conventional probe measurements.

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Coherent structure of large scale eddies and turbulence within the upper surface shear layer of a wind-driven current has been investigated by utilizing several flow visualization techniques. In the region of transition from laminar to turbulent flow, the visualization demonstrates the existence of a streak structure which can be shown in a plane view at the level close to the water surface and reveals that longitudinal vortices existing near the surface are responsible for the appearance of the streak structure. As the stream goes down into the region of turbulence, the flow field related to these vortices develops into that of tree-dimensional 'hairpin' vortices. A tentative model is presented to describe the evolution of these vortical flow field from a viewpoint of local instability due to the longitudinal vortices themselves.

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Interaction of vortex filaments at high Reynolds number is visualized using a schlieren method. 1) Several vortex rings are ejected in series along the same axis into still air through a circular orifice and the interactions of them are analyzed. 2) Two vortex rings are ejected simultaneously from two identical circular orifices separated a certain distance and their merging, splitting and interchanging are observed. These interaction phenomena are compared with the numerical results using the discrete vortex method.

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A new system for measuring the location of shock wave on an airfoil in transonic flow has been developed. This consists of a schliern optical system, a solid state linear image sensor as detector, video signal gathering unit and a micro computer. Using this system, the behaviour of shock wave fluctuating with high frequency on a airfoil such as the instantaneous location, the frequency and the amplitude can be measured with ease, which have otherwise been very difficult and toublesome to measure.

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A condensation shock wave caused by rapid expansion of moist air in a supersonic nozzle has been visualized by schlieren method and laser holographic interferometry. The flow field has been also calculated numerically by the method of characteristics and the distributions of static pressure along the nozzle axis have been measured. Based on these experimental and calculated results, the flow field in which a condensation shock wave has been clarified.

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The influence of velocity-profile distortion at the diffuser inlet on the flow pattern in the combustor was investigated with the hydrogen bubble method, for the combustor with dump diffuser and the combustor with conventional diffuser. The result shows that the combustor with dump diffuser is insensitive to the distortion in comparison with the combustor with conventional diffuser.

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An ordinary full ship generates at the stern a pair of large longitudinal vorticies, called bilge vorticies. In order to make clear the generation mechanism of the bilge vorticies, flow fields were visualized around systematically simplified ship stern models in IHI circulating water channel. The hydrogen bubble method and the dye tracer method were used for the visualization. The experi-mental results suggest that the bilge vorticies are generated by the similar mechanism as longitudinal vorticies generated at tips of reversed delta-wings, although bilge vorticies are distored and weakened in boundary layers and wakes of the ship.

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Discrete vortex method is applied to predict the flow behavior past a two-dimensional hovercraft with external air supply, and to know the mechanism of the interference thrust of the jet issuing from the clearance of the hovercraft in proximity of the ground moving at constant speed. In this paper, the transit flow behavior, the abrupt constant forward velocity of the hovercraft and the air supply, is calculated. There appear mainly three types of flow behavior; (1) the discrete vorticies flowed out from the front edge of the hovercraft are flowed to the downstream along the upper surface of the hovercraft without the concentration of vorticies in the case of small mass flow, (2) the concentration of vorticies develops but it is flowed to downstream along the upper surface of the hovercraft, and (3) it becomes large with the increase of mass of air supply and is standing in front of the hovercraft.

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Studies of secondary flow in vertically standing rectangular-sectioned, strongly curved ducts whose radius of curvature 0.6 and 1.5 wer made.
The duct is 5 cm breadth by 6 cm thickness with 108 cm long upstream and downstream straight duct attached at both ends of the bend, the former is riser and the latter downcomer.
Reynolds number for the test considered from 260 to 2740 in this studies.
Mean longitudinal velocity contours obtained by laser-Doppler velocimetry, pressure distribution along the inner and outer walls, and still and cine photography recordings of flow-streak were made.
In comparison with two curvature, there are striking discrepancies in flow patterns between them, found in these studies.

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Particle dispersion and recovery test are often employed in performance testing of clean rooms in order to verify the laminar airflow throughout the work zone and the capability of the clean room to limit the dispersion of, or recover from the effects of internally generated contamination. In these tests commonly used is a smoke tracer method, which inevitably pollutes test objects.
The patterns traced by smoke appear to be closely related to turbulence intensities of the airflow, which can be easily measured together with air velocities. For the purpose of substituting the turbulence intensity measurement for the smoke method, comparative tests in the clean room laminar flow were carried out between the flow visualization by use of a luminous mini-tuft as well as smoke tracers and the turbulence intensity measurement by a hot-wire anemometer. The test results are shown in Fig. 2, 3 and 4 and the substitution seems to be promising.

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Recent semiconductor industries have come to require ultra-clean spaces as production environments where the cleanliness level is strictly limited to less than 10 particulates of 0.1μm and larger per 1 ft ³ . In order to create and maintain such clean spaces, we should control not only the density but also the individual behavior of such fine particulate, which are expected to coincide with the airflow.
In this report, we visualized the airflow pattein in a model clean room by injecting the tobacco smoke through nozzles into the upstream of the linear flow with outlet velocities of 15 to 45 cm/s. We took pictures of airflow patterns including disturbance due to the presence of the static and the moving objects. We discussed some basic patterns in comparison with the numerical results of solving the two-dimensional Navier-Stokes equation. An 8mm film of the airflow patterns will also be shown at this Symposium.

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As a basic research on film-cooling of turbine airfoils the experiments of flow visualization of the water model flow was carried out. The flat plate model with a single round ejection hole was used and its flow was visualized by the dye injection and the H2-bubble tracer methods. The horse-shoe vorticies and the arch-vorticies with the boundary layer were clearly visualized in low Reynolds number condition. I n high Reynolds number condition, the basic flow become turbulent and no horseshoe vortex was visualized by those visualization methods.

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To understand the behavior of intake flow in a diesel engine, the pattern of air flow induced into a motored model engine is visualized at every crank angles during intake process by using a spark tracing method. Furthermore, the flow direction can be determined with tuft or tracer method, and, thereby, the flow velocity is also calculated from the visualized spark timing line.

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By means of the white-light speckle method, flow patterns can be identified and, moreover, quantitative velocity distributions of the whole flow field can be determined. This method has been applied to the measurement of velocity distributions of surface flow in a vessel or in an open channel.
When this method is applied to the measurement of inside flow, in certain cases, the specklegram has some inhomogeneous regions due to the turbulence of flow or the property of seeding particle, and yet it gives useful information about the flow state.
Present paper shows the measurement of vertical velocity distribution of the steady flow in the open channel and velocity distribuiton of the whole flow field in the peristaltic pump by means of the white-light speckle method.

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The instantaneous transverse position of the tracer particles in water channel is classified by the quantity of the illuminance of the particles.
The distance decay of the illuminance and the distance decay of the absolute value of the optical transfer function concerning with the image of the particles are mainly utilized to the measurement of the position of the particles.
The two-dimensional velocity distribution in each dividing section is caluculated by the application of image processing.

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Flow-birefringence technique using a suspension of milling yellow dye in water is applied to low-Reynolds-number flow around the following obstacles:(l) a circular cylinder, (2) two circular cylinders in a line with uniform flow, (3) an isolated sphere, and (4) a pair of spheres in a line with uniform flow. Photographs of isochromatics and of isoclinics are analyzed to obtain streamlines around the above-described obstacles. These results show the validity of Oseen approximation for uniform flow around these obstacles at low Reynolds numbers. Numerical calculations of streamlines around a pair of spheres, described in the appendix, show the details of closed vortex regions between a pair of spheres.

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Investigations in the present paper have been made theoretically on a breakdown and a development of the Karman vortex street in both positively and negatively buoyant wakes. Unsteady numerical solutions are obtained by means of time-dependent numerical analysis. To verify the validity. of the results of numerical analysis, results of flow visualization were compared with numerical solutions. The following results were obtained.
1. The natural convection from the cylinder has a remarkable influence on the Karman vortex street.
2. In the positively buoyant wake above a heated horizontal cylinder, the Karman vortex street breaks down.
3. In the negatively buoyant wake, the Karman vortex street develops.

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The developing laminar flow in a curved square channel was solved by using a finite-difference approximation adopted for the time dependent three dimensional N-S equation in toroidal coordinates. The channel consists of a 180° bend with curvature ratio 4, an inlet length of 5 hydraulic diameter and at the outlet 55 hydraulic diameter. The Reynolds number employed is 500.
Effects of diffusion term in the main flow direction observed are : a shift of incoming flow towards the inner wall at the beginning of curvature, and deadly retarded main flow appeared firstly near the corner of the outer wall, then secondary at the central region adjacent to the inner wall of the curved channel.

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To investigate the relations between flow structure and velocity fluctuations in the vortex growth in bounded jet flow, the full Navier-Stokes equations with the primitive variables are solved by a finite difference method, and the process of vortex growth is visualized by marker particles. The vortex growth in. bounded jet flow can be distinctive. Firstly, to attract the feature, two-dimensional jet flows are investigated. Then, in comparison with the two-dimensional case the bounded jet flows are discussed. The vortex growth in a wall shear layer may be explained by same manner as in a free shear layer. From this point of view, three-dimensional vortex structure in the bounded jet flow can be explained.

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Turbulent flow in two-dimensional channel with rectangular turbulence promoters has been predicted numerically by Large Eddy Simulation (LES). 9, 000 grid points were distributed on three-dimensional co-ordinates. Timelines, streaklines, Strouhal number of vortex shedding and so on were calculated, and also compared with those of the flow visualization experiments by use of dye-injection and hydrogen-bubble methods. It is shown that the large-scale structure of the flow around the steps can be described well by LES.

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In order to measure void distributions across pipe flow and to determine the transient flow pattern during blowdown from a high pressure water vessel to atmosphere, we have developed a high-speed scanning X-ray void fraction meter. The scanning. X-ray beam is collimated by 8 hole-slits on a rotating disc. An X-ray beam scans across a pipe from top to bottom, according to the hole-slit movement. The maximum scanning frequency is 200 Hz. A void distribution curve can be obtained every 5.0 ms. Void signals are sent to a void distribution color display system that make it easy to recognize even a slug flow. Experimental results show that the system is very effective to determine how flow patterns change during blowdown.

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When discussing two-phase flow phenomena (heat transfer, fluidflow etc) it is very important to judge the kind of flow pattern. Usually, flow pattern is judged by direct visual observation and photographs. However, these judgement is open to considerable uncertainty and test conditions are limited to the low pressure and simple channel configulation(tube). This paper efforts to judge the kind of flow pattern, using the X-ray CT(computed tomography) scanner, in the simple channel(tube) and the complex channel(4×4 rod bundle).

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An aerodynamic performance test for gas turbine nozzle vanes has been conducted under aerodynamic design conditions. The effect of endwall cooling on the performance has been surveyed by measuring detailed pressure distributions at a certain exit flow section of a nozzle vanes' annular cascade with the use of a Pitot-tube. Image display of a series of pressure fields clearly reveals variations of patterns due to differences in an injection angle and amount of injected coolant. Among various kinds of two-and three-dimensional display modes, two dimensional step color mode has the most powerful ability for analysis and presentaion of data, although it considerably loses its virtue when published in black/white print. Image display, as a means of expressing a large quantity of data, is getting indispensable under recent advancements in wide varieties of computer systems, irrespective of experimental-and numerical-work.

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An image processing system applicable to flow visualization experiments has been developed for making a quantitative estimation of unsteady two-dimensional flow fields. The flow with which we are concerned is that past a circular cylinder at Reynolds numbers around 100. The flow visualization is conducted in a towing water tank by means of a tracer method, and produces photographs of particle streaks. These photographic images are then put into an optical scanning process followed by computerized digital image analysis. This generates an instantaneous velocity distribution of the flow concerned; the mesh point velocity is interpolated from among several to several tens of local velocity vectors, and numerical calculations are made with thee distributions of stream function, vorticity and pressure. Distributions are presented in the form of contour lines.

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A method of flow-visualization was applied to ellucidate the three-dimensional characteristics of coherent structures near the bed of uniform open-channel flow.
Flow patterns in horizontal cross-sections of the flow were visualized. The pictures were digitized and analysed by computer system. In the results, two-dimensional distribution of some of the hydraulic variables such as velocity, streamlines and velocity correlation coefficients were calculated and displayed as graphical outputs.
These results brought forth an assumption of frozen turbulence along the longitudinal line, which enabled the authors to calculate the upward components of velocity vectors. On the basis of thus-obtained, three-dimensional distribution of velocity vectors, coherent structure of the flow near the channel bed was ellucidated.

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A method to obtain two dimentional distribution of Richardson number is proposed. The distribution of density is visualized by dye (methylene blue). a photograph of dye distribution is taken with a plane light source placed on the opposite side of the experimental channel. Standard solutions of dye are placed on the channel for calibration. The distribution of velocity is visualized by hydrogen bubble method. photographed with a slit-light from the bottom of the channel. Photographs of dye and hydrogen bubbl es are taken alternatively.
These photographs are processed by a video camera. an AD converter. an image memory and apersonal computer to yield 512×480×8 bit intensity data. The intensity data are processed by a universal computer to calculate the distributions of density. velocity and Richardson number. A rising velocity of hydrogen bubbles is corrected by iterative calculations, a spline interpolation is applied to the horizontal direction, the equation of continuity is used to obtain the vertical component of velocity.
An application of this method on density current is shown.

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