One of our principal aims in flow visualization has been to quantitize the observed flow phenomena through digital image processing. Recently, a new trend has been developed in the reverse way: to produce the image of flow phenomena from computer-generated data using color graphic techniques. The latter method can also be used in reconstruction of the experimental flow field from limited data to give more physical meaning to the information. This technique permits a numerical (computer) experiment to be visualized much like a physical one and thus help to speed up the interpretation of physical phenomena.
This study-surveys the literature pertinent to flow visualization by means of computer-generated color graphic techniques. Both the methods and applications are included.

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Laser speckle photography is a simple and useful non-contact method of measuring in-plane surface displacement of an object. An image analogous to the specklegram can be obtained by using a white light source by means of preparation of an artificial speckle pattern in surface of the object. This method, called "a white-light speckle photography", can be applied to measuring two-dimensional velocity distributions of fluid flows. By this method, not only quantitative velocity distributions, but also contours of velocity in any direction and qualitative visualized flow patterns are obtained at a time.
In this report, surface velocity distributions of flows in a cylindrical, shallow vessel turning on its axis and in an open channel are measured by means of the white-light speckle photography.

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Tracer method was applied to visualize the three-dimensional structure of turbulent open-channel flow. The horizontal cross-section of the flow illuminated by light through thin slit was shifted upward and downstream. At the same time, pictures of flow patterns were taken every half a second by the camera mounted above the channel. Illuminated cross-section and the camera were both shifted downstream with mean velocity of the flow. Pictures obtained were processed by computer system and distribution of velocity vectors, rotation and two-dimensional divergence were displayed concerning each horizontal cross-section of the flow.
On the basis of these results, downward or upward motion of fluid such as boils, bursts or sweeps were illustrated precisely and their distribution in three-dimensional flow field and their relation with eddy motions were made clear.

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Typical structures of large scale turbulence in a pipe flow was investigated by a visualization of behaviour on a surface of dye layer on a whole bottom of a pipe with squared crosssection. The dye layer was generated by contineous injection of fluorescent dye into a viscous sublayer. 16mmcinemovie of the behaviour on a surface viewed through a transparent upper wall show the longitudinal streaks which join or separate again and again. In these behaviour, some typical patterns are found. The relations between ejection and high-speed flow are made clear from the correspondence of these typical patterns to instantaneous velocity flucuations, measured simultaneously by Laser-Doppler velocimeter.

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Two circular cylinders in tandem arrangement were pulled in a tank filled with glycerin.
Both of C_Df and C_Dr become smaller with decreasing the gap of two cylinders, where C_Df and C_Dr imply the drag coefficient of the upstream cylinder and that of the downstream one, respectively.
In the case of two equal cylinders, the value of C_Df/C_D and C_Dr/C_D are about 0.6?0.7 and 0.5?0.6, respectively, at ε/a=0.2 and in the range of 3×10^-2<R<1.5×10^-1, where C_D is the drag coefficient of a single cylinder in a uniform flow, ε the gap of two cylinders, a the cylinder radius and R the Reynolds number.
In the case of two different cylinders in the radius ratio 3:1, both of C_Df and C_Dr of a small cylinder are always smaller than that of the case of two equal cylinders at equal Reynolds numbers. There exists separation bubbles in flow fields between two cylinders at ε/a_s <5, where a_s is the radius of the small cylinder.

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The turbulent structure of an open channel flow with two flood plains were investigated experimentaly. We used tow kinds of channels which were a straight one and a curved one. Velocity measurements were made by following two methods : 1) measurements of velocity components with a hot-film anemometer and 3mm diameter propeller flowmeter, 2) measurements of longitudinal velocity component on a free surface using the flow visualization technic of Cameron effect. Main results obtained through experiments are as follows : 1) the upward flow from the edge of flood plain to the free surface exists in a straight channel and a curved one, 2) in a curved channel the turbulent structure is described by three independent spiral motions and two upward flows.

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Recently, flow visualization is used to make a study of sand wave. In view of the fact that the formation of sand wave is due to the structure of flow, such a study is effective and significant. In this paper, we carried out flow visualization on the ripple models as the fundamental study of the mobile bed. The flow patternes, the eddey scale on the wake area and the length of the reattachment point were obtained by these observations.

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Time-dependent flow fields around 2:1 elliptic cylinder and 5:1 arc wing at angle of attack 45° were observed by alminum powder method. At the same time, lift and drag were measured. At the initial stage after starting, first sharp peaks in lift and drag occur and then vanish. After this, lift and drag begin to increase again and the second peaks appear. The first peaks in lift and drag occur when the potential flow is formed around the body, and the second peaks occur when a large vortex, which is separated from the leading edge, is formed on the rear of the body.

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Spark tracing method was used to visualize the pattern of air flow induced into cylinder of a motored model engine, which consisted of a transparent plastic cylinder with an exhaust magnetic valve on its top.
The spark time lines of the air flow were photographed simultaneously by three cameras located on each direction, over-head, front and side.As the resilts, the pattern of air flow was found to be much affected by the positions of the piston(denoted by crank angle θ)and of the spark electrodes(β).

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In order to investigate the duct effects on the flow coming into a propeller in a duct-propeller system, flow visualizations were conducted by an oil paint method combining 16 mm movie film recording. Two kinds of duct shapes, namely an accelerating type and a decelerating type were tested locating them in front of the propeller in open-water condition with a thin plate in the center plane of the propeller. A shot of the film was taken every 2 seconds and projection is made at the normal speed of 24 frames per second to see the phenomena in accelerated mode. It was confirmed that this method was very useful to see the process of peeling of the paint off the plate surface and of stream lines allowing for more detailed physical investigations of flows.

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In order to get a better understanding of the so called bow-wave-breaking phenomenon occurring on full-bodied hull forms, attempts were made to observe the flow field around the bow of ship models. By use of dye particles injected into the fluid, it was verified that there exists a shear layer beneath the free surface in front of the moving body. Then it was found that the shear layer leads to the formation of necklace vortices spiraling around the bow of the full form even at extremely slow speeds without any visible breaking waves. At higher speeds there appears a visible wave breaking accompanied by intensive vortical motion beneath the free surface. The intensity of the shear layer and the necklace vortices around bluff bows thus seems to have a significant effect on the formation of breaking bow waves.

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The three-dimensional wing with winglet has lower induce drag and larger lift-drag ratio than without winglet. In order to save the power for ship propulsion, the research on marine propeller with small wings at blade tips, i.e."Bladelet Propeller", was carried out in the circulating water channel, using series model propellers had 300mm diameter. The flow visualization used in this experiment was the oil film method and surface tuft method. It was obtained the guide for the design of bladelet by this experimental result.

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It is very important to study about the inner flow of rotating impeller of hydraulic machine as pump etc. for the improvement of it's characteristics. Up to now, there are some examples of the flow visualization for the centrifugal pump of water, but is none for the pump of oil.
For the centrifugal pumps designed for water, its sphere of use are spreaded and it became to use for the transportation of the high viscosity fluid as oil. But in this case, the characteristic of pump become lower for the increasing of viscosity. So, it became important to increase the efficiency of it by studying of growing eddy and separation etc. in the inner flow.
In this study, the inner flow of centrifugal pump for oil was observed using Tuft method and the characteristics of it was made clear and the data for improvement of characteristic was obtained.

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A Sirocco fan is generally used in automotive air conditioning system, which is very compact, and has a high flow resistance. The operating point of this system is also changed by blowing modes, such as room recirculation and fresh flow. This paper presents the flow visualization between blades and in rotor, obtained by the polystylene tracer method in water. Flow between blades was taken photography by a camera synchronized with the rotor rotation.

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Design theory for cross flow fans is not established well in general, although it is widely used for home and office appliances. An equation concerning aerodynamic characteristics of cross flow fans is derived here based on Euler's pressure equation. This equation contains, however, an unknown parameter which cannot be determined easily by theoretical analysis. New flow visualization technique in water is developed using the surface tension modifier as the tracer, in order to overcome this difficulty and analyze the characteristics of the parameter experimentally for wide flow range. Certain relation between the unknown parameter and the fan configuration is obtained, which would contribute to the improvement of modeling of the flow field in cross flow fans.

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The flow visualization of two phase jet flow were conducted at a variable cylinder. Visualization techniques consist of the smoke wire and vapor screen methods and image processing.
From these results, it was assumed that it become possible to visualize the two phase jet flow in a variable cylinder by using the vapor screen method.

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Until now the flow birefringence method has been used to observe the steady state flow. We applied this method to observe the flow around a Spark-induced bubble. When a cavitation bubble collapses near a solid wall, the bubble deforms from its spherical form and a microjet arises against the solid wall. We use the birefringence method to show the appearance of this microjet.

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The quantitative agreement of our results(1981) on the isochromatic and isoclinic trajectories obtained by gel birefringence method with the theoreticcal values computed after the standpoint of Philippoff(1976) on the possible operation of the deviatoric normal stresses in the Newtonial liquid flow, suggested a need of further experimental evidence of the effect of the local displacement vector in jelly on the birefringence response. The present paper is concerned with this view-point, where the measurements on the tracer carbon particles and on the deformation models of the binary mixture particles of poly(dimethyl siloxane) and monochlorobenzene were carried out for their dispersed systems in 15 wt.% gelatin jelly solidified in geometrically similar ducts to those used by Durelli and Norgard (1972). Observed data, when compared with those reported by Durelli on liquid flow, showed a good coincidence of the tracer displacement loci with streamlines along with thier linear proportionality of the displacement vector to the liquid velocity. On the other hand, each initial spherical droplet of dispersion deformed by a certain degree of variation into ellipsoid with its longer axis rigorously inclined to the local direction of extensional principal stress of the matrix by the same angle as the extinction one.

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In order to clarify the dynamical switching mechanism of attachment jet by control jet in wall attachment device, the switching processes were observed by the visualization technique of flow pattern and pressure distribution applying Moire topography to free-surface water table.
The observation were performed at Froude numbers of 0.5 to 0.8, which correspond to Mach numbers of air jet, and at various control flow rate between 30 and 70 per cent of the attachment jet's supply flow rate. The similarities in static and dynamic bihavior of hydraulic and gaseous wall attachment devices were recognized.
It was found that the factors affecting the switching action are the initial deflection of the jet and decreasing or vanishing pressure gradient across the jet owing respectively to the momentum and the flow of the control jet. At high control flow rate, a storong vortex caused by control jet's entrainment kepps the attachment jet from switching in its earlier stage.

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The velocities, accelerations and drag forces experienced by two equal spheres freely-falling along their line of centres, or by two equal-sized spheres linked each other with a fine string, are determined at low Reynolds numbers. In contrast to the theoretical results obtained by applying the Stokes approximation for two equal spheres, the upper sphere falls faster than the lower sphere and the drag coefficients vary with Reynolds number even at the Reynolds numbers below 0.1. Flow visualization technique described in part 1 is applied to visualize streamlines around pairs of spheres falling along their line of centres.

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In order to confirm the theoretical results of the diffraction of linear plane wave concerning with the cylinders, the experiments of visualization are studied by using ultrasonic wave. In the experiments of visualization, Schliren Method is improved by using stroboscopic light source. As the experimental results, the images of phase and diffraction of sonic wave can be obtained at the same time. The theoretical results of the diffraction are verified to be reliable in comparison with the experimental results.

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The unsteady rarefaction wave generated in the double diaphragm shock tunnel by rupturing a light diaphragm placed between the vacuum and the test gas sections has been investigated experimentally. The diaphragm motion has been visualized by a sequence of Schlieren photographs. This has been found to be useful in order to locate the path of the diaphragm fragments after the bursting within the rarefaction wave in the (x-t) diagram. It has been concluded that at Mach number equals 4.25 the light diaphragm does not tear off, while at Mach number equals 7, it has been torn to fragments due to the impact of the primary shock wave and the higher temperature. The data reduction agrees well with the emission-absorption measurements.

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In this paper, downs dyed in fluorescent dyes and chopped fine are used as the tracer of air in order to visualize stream lines of the air current generated by rotating a propeller without movement.
Lighting is made by using fluorescent lamps with black light which radiates only ultraviolet rays. The propeller is put between lights which are situated in the upper and lower sides of that.
As the result of this experiment, comparatively clear stream lines are obtained, though the thickness of lines is not uniform since it is difficult to make equal the size of fine downs.

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The flow in the clearance between a rotating disk and the casing was studied by the use of a flow visualization technique. The experiment was conducted for several clearance ratios s/R from 0.0080 to 0.120. At large clearance ratios, three different types of instability were observed near the casing wall. The two of these instability were similar to the instability in the Ekman layer. At small clearance ratios, only one type of instability was observed. It was found that the boundary layer on the rotating disk was stable for exceedingly large values of the Reynolds number. The effect of throughflow on the stability of the flow was examined.

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It becomes widely known that there are low speed streaks and high speed streaks in the linear sublayer. Though low speed streaks is the origin of the bursting process, it is not clear how this pattern of low speed streaks is matched to the more random secondary motions. Until now, authors have visualized the attractive imbricate shape motion in the wall layer by flow visualization method named AMD and have investigated the relation between this pattern and bursting phenomenon. AMD flow visualization method is one of the mixing tracer method, this tracer is constituted of Aluminum dust, condensed milk, and dye water. One of the feature is the selection of the visualizing object by means of the regulation of the injecting liquid. In this paper low speed streaks in the linear sublayer is visualized and considered by means of the combination of flow visualization methods, e.g. AMD method, Alminium dust method, hydrogen bubblemethod.

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Wake flow behind a circular cylinder with a flat step is visualized by dye-injection method and measured by hot wire anemometer. Vorticies of wake flow with different shedding frequencies change its relative locations with time. I-type connection, phase change, Y-type connection and disjunction repeat periodically. RMS values of fluctuating velocities have a maximum at I-type connection and a minimum at Y-type connection.

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Flow Visualization in gas dynamics gives clear idea about variation of pressure and density variation and type of flow developed in the test section. It covers a broad spectrum instead of measurement of parameter at a point. The flow may be steady or unsteady, the techniques for taking photograph also differ.
Experiments including flow visualization were performed on three devices i.e. Air Ventilator, Subsonic Closed Cycle Wind Tunnel and a Shock Tube. In the case of Air Ventilator a smoke tunnel is used to provide facilities for visual investigations of air flow phenomenon occuring in the study of aerodynamics. The tunnel is a two dimensional, condensed version of large smoke tunnel. In its operation, smoke filaments pass over the different test models to provide the effects of Air Stream behaviour. It is a fixed unit and is designed so that the test models can be changed rapidly with the minimum effort. The photographs of visual observations are taken for permanent record. The paper presents the construction of smoke techniques and interpretation of photographs taken with different aerofoils and different angle of attack. The experiments on closed cycle Wind Tunnel give the set up for experimentation and Schlieren Photography. The experiments were conducted to find suitable Wind Turbine Rotors.
Flow being unsteady in the Shock Tube the experimentation in addition to using pressure transducers, thin platinum resistance thermometers, in corporates short duration light source for Schlieren photographs. Storage Osciloscope is used for recording pressure and temperature traces.
All the three rigs are locally fabricated. The visual phenomenon covers subsonic to supersonic flow. The paper also presents the design and description of the instrumentation used.

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The scavenging performances of 3 kinds of uniflow type scavenging port were examined with special model engine which had transparent cylinder.
For each port, flow pattern of the intermittent flow of scavenging air in the cylinder was visualized by adding mist of methylnaphthalene, and was observed using a high speed camera.
From the result of this experiment, some causal relations between the shape of the uniflow scavenging port and the scavenging performance were clarified.

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The purpose of this study is to make clear the possible effect of thermocapillary (Marangoni) convection on the growth of crystal which is made by such techniques as Czochralski, floating zone, etc. Horizontal layers of liquid in open rectangular containers with different geometry were heated from the vertical side walls or from bottom wall and cooled at the middle part of free surface. Characteristics of heat transfer and convective flow driven both by buoyancy and surface tension gradient were measured under different combinations of geometrical and thermal factors.

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The Dean's hydrodynamic instability in curved rectangular channels having the aspect ratio of 12 has been examined by flow visualiztion technics, Using a dye injection and an electrolytic coloring methods, the effect of curvature ratio on the critical Dean number has been determined over the range of curvature ratio from 0.0125 to 0.25. The results of photographs indicate that the critical Dean number for the onset of instability increases with increase of the curvature ratio for the region above the threshold point of 0.1, wheras it is nearly constant over the range of lower curvature ratio. The pair of vortices due to the two side walls is quite clear but is confined into the corners near the side walls.
The results also show that the wave number of secondary flow becomes large for Dean number well over the critical value indicating transition to the next stage of the oscillatory phenomenon.

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Buoyant plume above heated horizontal cylinders observed by thymol blue technique and thermal structure have been measured by thermocouples in a shallow water layer with a free air interface. Hydrodynamic conditions are characterized by the swaying motion of laminar plume above cylinders. Recirculation is induced when the plume interacts with the air-water interface or with the adjoining plumes. Temperature measurements and flow visualization reveal the existance of unstable temperature gradients below the interface and nearly isothermal region extends from the mixing layer to approximately the level of the cylinder and stable temperature gradient below the cylinders.

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Temperature-sensitive liquid crystals are used to visualize an instantaneous temperature field close to the wall associated with the organized motions in a flat plate turbulent boundary layer without pressure gradient. A very thin liquid crystal membrane has been attached on the wall surface, which is heated with a constant heat flux in a low-speed water channel. By virtue of the color change of liquid crystals with the simultaneous hydrogen-bubble flow visualization, the existence of high- and low-temperature streaks near the wall is revealed. The high-temperature streaks are mostly associated with the so-called low-speed streaks, and the low-temperature streaks with the high-speed streaks. The measured spanwise spacing of high-temperature streaks is 81υ/u^*, while the streamwise length is confirmed to be more than 1000υ/u^*. These observations provide new evidence regarding the turbulent heat transfer mechanism in the wall region of turbulent boundary layers.

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In order to study the effect of unsteadiness on the transition to turbulence in boundary layers, measurement of velocities in the purely oscillatory flow and also that in the steady uni-directional flow have been made, the former having been performed in a large oscillating tunnel. the flow visualization technique of thin-layered milk method developed by the senior writers has been used for clarifying the difference between the transition phenomenon observed in the case of oscillating boundary layer and that in the case of steady uni-directional flow, employing the same water tunnel.
The comparison made between the two cases shows that the processes of transition to turbulence are basically similar in the both cases, but that the initial disturbances formed during the deceleration period of the oscillatory flow have relatively strong characteristic of two-dimensionality and do not have the appearance of forming such turbulent spots as in the steady uni-directional flow, the character of disturbances formed in which is of more three-dimensionality.

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Autorotation phenomena of a thin elliptic cylinder about its spanwise axis is studied experimentally and numerically. Flow field was visualized by smoke wire method in wind tunnel using multi-exposure storobo-light synchronizing with the rotation, and by aluminum dust method in towing water tunnel. Variations of the lift, the drag, the moment and the torque coefficients with the rotating angle were measured using the strain gauge balance.
Numerical simulations using discrete vortex method were carried out for the same condition as to the experiments. Agreements between them were good.

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Recently the size of magnetic disk memories becomes larger. And now, disk fluttering is an important problem. Yet, few studies about this problem have been performed.The flow between two parallel rotating disks has been visualized with aluminium flake or coloured water. However, photographs obtained by these methods were not clear.
We studied especially about central-cramp type disk pack without center air blow-off. And by means of smoke wire, we obtained clear visualized photographs of the pattern of the air flow between the disks. These photographs show that the shroud makes the flow stable, and that espesially when the spoiler is inserted more than about one-third of the disk radius, the flow becomes extremely stable.

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By use of smoke-wires outside the turbulent region of a plane air jet, the entraining fluid was marked and thus the passage of turbulent large-scale structures was detected from the contortions of the turbulent-non-turbulent interface. These structures were observed to be highly three-dimensional, having considerable amount of streamwise vorticity in the trailing region. The occurrence of these structures was highly non-periodic with no detectable correlation between their occurrence across the centerline. The engulfment of the entraining nonturbulent fluid takes place predominantly in the trailing region of the coherent structures. Even though the details remain to be established, this study reveals that the large-scale coherent structures in the self-preserving region of the plane jet is highly complex.

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This paper reports flow visualisation studies on a sphere of 250 mm dia. for both stationary and rotating cases with jet flow and rotating sphere without jet. Nozzle of 10 mm dia was used. China Clay technique was adopted to visualize the flow pattern. The studies have been carried out by varying the following three quantities (1) Jet Reynolds numbers (2) Ratios of gapheight to nozzle dia (h/D ratios) and (3) rotational Reynolds numbers. Experiments were also conducted with trip wires of different cross sectional areas and different sizes of the rings to precipitate transition to turbulence for sphere rotating in stationary ambient. Attempts are made to prevent the flow from bottom hemisphere by placing different sizes of circular discs below it, for sphere rotating in stagnant ambient. Photographs were taken for all the cases.
Results in the case of sphere rotating in stagnant air reveal good confirmations of previous results. Results in other cases are with the ultimate exposure of qualitative indications of nature of flow. Increasing jet Reynolds numbers and decreasing h/D ratios increase the stagnation zone in the impingement region. Under the conditions of study, flow is found to be turbulent in all the cases with jet. Changes in jet Reynolds numbers and decreasing h/D ratios increase the stagnation zone in the impingement region. Under the conditions of study, flow is found to be turbulent in all the case with jet. Changes in jet Reynolds numbers and h/D ratios have least effect on the nature of flow. Rotation has a marked effect on the flow pattern and hints at the presence of possible embedded vertices in certain cases of rotation.

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A flow visualisation technique has been used to determine the pattern of flow behind bluff bodies in a square duct. A V gutter with closed base, a square prism and a cylinder have been used as bluff bodies, all the bodies having the geometric blockage of 37.5%. The flow patterns have been obtained using oil flow visualisation technique for inlet velocities of 10, 15, 20 and 25 m/s. From the flow patterns obtained, the geometry of the recirculation zone formed behind the bluff bodies has been determined. The method is very useful in determining the geometry of recirculation zone formed behind bluff bodies accurately in two-dimensional flows. These studies have extensive application in combustion research to find the effectiveness of bluff bodies. Moreover, flow pattern informations can be used to validate numerical methods used for the prediction of recirculating flows.

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A new technique of tandem hot-wire probe has been developed to measure the two-dimensional unsteady sepalated flows including backflow region around rectangular prisms at Reynolds numbers ranging from 10⁴ to 10⁵. Measurements of time-averaged and unsteady velocity distributions are made for stationary and oscillating models. The time-averaged and unsteady streamlines around these models are presented and their correspondance to aerodynamic forces are also discussed.

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In this paper, initial flows around an uniformly accelerated elliptic cylinder in an incompressible fluid are analysed from at rest by the finite difference method, and time histories of streamlines, equi-vorticity lines and drag coefficients are shown. The numerical schemes used here are the DuFort-Frankel technique for solving the vorticity equation and the DuFort-Frankel technique for solving the stream function. For the latter case, the discrete Fourier transform and the Gauss elimination are applied to the analysis of a block tridiagonal matrix. Especially, with 70 average iterations per time step for the SOR method, the Fourier series method are verified to be more than 10 times faster.

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Three-dimensional laminar-flow development in a curved pipe has been investigated by using flow visualization technics. The hydrogen bubble and the powder of pumice used in Japanese painting were applied to traice the main and secondary flows, respectively. The thermal and refraction compensators were found to be needed for improved results. The results are obtained for the locations at 0°, 22.5°, 45°, 90°and 180° from the beginning of the curved pipe led by a long leading straight pipe under the flow conditions of Reynolds number 1000, Dean number 333 and the curvature ratio to be of 1/9.
As a result, the overshooting phenomenon of the main flow distortion towards the outer wall due to the centrifugal force in the midst of the development is clearly identified and an overall comparison is made with the available theoretical results in good agreement.

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In general, ship hull forms are so complicated that the flow visualization has not been easy. The authors complete a ship model with transparent hull in order to study on new experiments of flow visualization around hulls and propellers, Using the transparent ship model, not only flow visualizations can be made from inside of the model but also the lighting from inside is possible. Especially, direct measurements of the cross flow angle will be widely applied by means of the observation of tracer's flowlines from inside of model.
In this paper, a transparent ship model and some applications are introduced as follows.
1) Observation of streamline by tracer method.
2) Observation of the distribution of cross flow angle by use of the H₂ bubble method.

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In order to reveal the entrainment mechanisum of ambient water and the transition mechanism into fully developed turbulent jet, it is necessary to investigate the processes of the vortex formation, growth, coalescence and breakdown in near-field of jet by means of both visual and anemometry measurements. We(1980)¹⁾ have examined visually the effects of the Reynolds number and the nozzle length, i.e.initial boundary-layer thickness, on the coherent vortex motions in a two-dimensional free jet, and observed two kinds of vortex patterns; one is 'varicose' pattern and the other is 'sinuous' pattern.
The present paper is firstly to examine the effects of the bottom wall(Fig.1) and the free surface (Fig.2) on the coherent vortices in a horizontal plane jet, by making use of hydrogen-bubble method. Although the vortex production may be not strongly affected by these boundary conditions(fig.3), the vortex growth is fairly restrained due to the bent flow-axis(Coanda effect). A noticeable feature is that there exists a pair of coherent vortices even in the wall jet(Fig.4), in spite of perfect suppression of the wall-side entrainment by the bottom wall.
Next, we have tried to analyze the velocity fluctuations of vortices by means of simultaneous visual and hot-film mesurements. The first spectral peak frequency on the flow axis coincides well with the vortex frequency obtained visually(Fig.9). However, this peak frequency in the coalescence region is lower than the vortex frequency(Figs.10 & 11), because the interaction between the pairing vortices may be so strong as to appear in the hot-film signals(Fig.12). Thus, we examined the probability of the vortex period on the flow axis, by using a conditional sampling method (u/u' [greater than or equal] H)(Fig.14). These results (Fig.15) also coincides well with visual data (Fig.7).

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This study made clear the flow field in a wall attachment amplifier using the hydrogen bubble method.
The model of fluidic element for visualization was Flip-Flop type logical unit. The working fluid was water. The experiments was done in the range of Reynolds number 200-700, and the control flow was changed from 0 to 20% in each case.

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