This paper describes observation of flow on a horizontal flat plate above a working propelle to understand the propeller-hull vortex cavitation(PHVC).
The flow on the plate is visualized with air bubbles in IHI Circulating Water Channel. It is found that the flow is divided into six patterns by two parameters, the propeller load factor, CT, and the ratio of tip clearance to the propeller diameter, c/D, as follows;
I Non-Reverse Flow II No-Vortex Reverse Flow III Aft Vortex Flow
IV Double Vortex Flow V Fore Vortex Flow VI Splatter Flow
The authors give the criteria of PHVC inception in the relation with the patterns, and discuss its vortex system.

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In order to make clear the difference of the characteristics between conventional propeller and highly skewed propeller, the flow visualization on the blades of propellers were carried out using oil film method.
The oil film consists of Cr₂O₃ and paraffin oil. Two types of propellers, four in total, were tested under different advance coefficients or Reynolds numbers. The results are shown in the schematic drawings explaining the difference of the flow on the blade among these propellers.

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High lift devices of airplane have been studied mainly for the airfoil and applied to actual airplanes. However, except very high-aspect-ratio wing, the planform of wing is also strongly contributive to the stall characteristics of the wing.
This study is to find better planform as well as better airfoil to get more aerodynamic forces(lift and drag) than the existing ones by changing not only the sectional profile of airfoil but also the planform of wing. The devices mainly. in addition to the existing flaps, consist of a set of wider slat and root flaps like strake which generates strong longitudinal vorticies and thus stablizes the flow around the wing at high angle of attack. Newly developed devices can also increase the drag coefficient as well as the lift coefficient and thus decrease the flight speed of airplane in landing approach. The flow vizualiza-tion by means of taft attached on the wing and smoke lines of paraffin mist Is helpful to this study for understanding the effect of the devices on the partly separated flow around the wing.

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This report presents the observations of laminar boundary-layer transition on wing surface of a light monoplane. Flight experiments were conducted on a single engine FUJI FA-200. The transition was indicated with the use of sublimating chemicals. The transition Reynolds number was about 1.3 million.

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In order to clarify the hysteretic characteristics of Wells turbine for wave power generotor, an experimental investigation has been made by use of a newly devised turbine equipment in which a sinusoidal flow condition is simulated. The results have shown that the hysteresis is more sensitive to solidity and blade thickness and less sensitive to Reynolds number and blade surface roughness. By means of flow visualization, it is found that the hysteresis is due to different behavior of wake between an accelerating flow and a decelerating flow.

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The relationship between the figures of the air path and the noise in refrigerator model is studied in this paper.In case that the distance from rear plate to fan-base is wide and the distance from blowing plate to fan-base is narrow, the air flow is found to be rotatory and smooth by visualization with Dry Ice, and more the value of the noise level is low.So not only the shape of the fan but also the figures of the air path should be concidered to reduce noise.

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On the purpose to examine a heat dissipation capability of fin in actual electoronic equipments, the effect of an obstacle above a fin on the cooling performances was experimentally investigated. The decrease of the distance from the obstacle affected natural air convection from the fin and reduced the heat transfer coefficient. The effect of the supply wattage, the fin temperature and the fin bight on the cooling Performances were also discussed.

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In order to interprete heat transfer data of practical plate compact heat exchangers with corrugate plates the three dimensional flow patterns in them were investigated by visualization using the smoke wire method.
Three types of test section were investigated; flat plate, "Ellipse" type and "Mount." type. The latter two were of corrugate type, and their plates had projections of ellipse and top-cut pyramid forms regularly arranged, respectively.
It was observed that the "Mount." type projection disturbes flow in the highest degree among three.
This fact well corresponded to our previous heat transfer data where the highest performance was attained with the "Mount." type plate.

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In the present paper, the mechanism of diffusing free doublet is described after the flow visualization. When an impulsive concentrated force is applied at a point in the uniform slow flow of incompressive fluid, a diffusing doublet (a pair of vortices) with the axis in the direction of the applied force is shed from the point of the drag application, and convected downstream with otherwise uniform flow velocity. The simple and fundamental two-dimensional unsteady phenomena were visualized in an open type single-return water tunnel by making use of aluminum tracer and hydrogen-bubble technique. Impulsive concentrated drag was applied by issuing some water containing aluminum powders in a moment through a slit with width 0.5mm, which was installed in parallel with the uniform flow. A ladder type of electrodes composed of tungsten filaments with diameter 0.01mm was used for hydrogen-bubble technique. The flow patterns were photographed continuously by a camera with power winder. The coordinates of bubbles on the photographs were read by a grafic digitizer, and the velocities of bubbles were computed by Wilkinson's numerical differentiation method.

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The hydrogen-bubble method was applied to visualizing turbulent pipe flow in the range of Re from 5×103 to 1.5×104. Platinum wires were set in a pipe cross-section so as to form a regular polygon periphery, from which hydrogen bubbles were generated continuously. The hydrogen bubbles were visualized by lightening cross-section to observe them from downstream by TV camera and their fluctuating bahavior recorded on video tapes was analized using personal computer image processing system.
Mean value of circumferential intervals between adjacent bursts decreases as the radial position of the platinum wires for generation of hydrogen bubbles approaches wall and has a limiting value of ?? 100 in the vicinity of the wall. Difference between flow structures in the buffer region and the turbulent region has been clearly indicated by drawing quasi-3D space-time profiles and contours of fluctuation of hydrogen bubbles.

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Supercritical stability conditions in stratified shear flow are discussed in this paper. Landau's equation of weak non-linear theory is usued in the theoretical analysis of this stability problem. The theoretical results are compared and confirmed with the experimental results using the methods of flow visualization.

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An aim in this paper is to clarify an existence of coherent structure in a turbulent plane thermal plume in a stable-thermally stratified fluid inside a comparatively large enclosure. First, the thermal plume could be observed by means of a flow visualization. Secondly, statistical analyses were carried out on time series data of the turbulent plane thermal plume. Finally, physical characteristics were made clear on visualized vortex pair in the thermal plume inside a thermally stratified fluid. As a result, main conclusions obtained as follows. (1) An existence of vortexes near the top region of the thermal plume was discovered by means of flow visualizations. (2) From the spectrum analyses of thermal plume, it was found that this vortex is generated in the transition region and is transported to the turbulent region. (3) This vortex is an ordered and large scale coherent motion.

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The structure of secondary flow induced in wavy channels have been investigated by the dye injection method.
The secondary flow is a kind of Taylor-Goertler vortices observed in a curved rectangular channel. However, the wavy channel is different from the curved rectangular channel in the processes of vortex development and destruction. It is found that an ustable mode in which the vortices formed at the upper and lower walls of the channel interact leads to the vortex destruction and significantly promotes the transition of turbulence.

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At the fundamental study of the three dimentional turbulent structure, visualization technique by dye injection methods and hydrogen bubbles methods were used. Experiment have done in the rectanguler open channel for small aspect ratio (B/H=0.2). In order to visualize the turbulent structures from inner wall region to outer wall region, water with FLUORESCEIN SEDIUM and vertical (or horizontal) harogen light sheet were used.
In this paper reration between the wall turburence and mechanism of secondary flows are described in detail.

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Flow patterns at a confluence were investigated by using the oil film method and the particle tracing method in open channel flow. From the visualized images, the existences of a secondary flow at a confluence and a stagnant region just upstream from the junction were suggested;which are strongly related to the local scour at a confluence in movable bed. Also, a simple method for obtaining the width of a dead water zone by using a dividing streamline was proposed.

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To quantify fluctuation of tufts on the hull surface of a ship model a method was introduced to freeze and accumulate continuously the instantaneous positions of tufts from VTR of conventional tuft tests. Then the maximum extent of fluctuation and the mean direction of tufts were determined by the aid of computer. The tuft fluctuation thus determined for two different ship stern forms were shown.

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Numerical simulation of typical potential flows has been carried out by a NEC personal computer system. Computer programs were written by Pro FORTRAN-77 on MS-DOS. Graphical solutions are presented in terms of drawing streamlines. Various flow fields can be easily obtained for some parameters, e.g. strength of a sink, a source, a vortex filament etc. These programs have been used for education of the third year students of our department.

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A extended theory of the wake-source model for a symmetrical bluff body of Parkinson and Jandali is presented for calculating the imcompressible potential flow external to an asymmetric bluff body and wake. Flow aroud an asymmetric bluff body will in general give rise to a lift force, and a circulation about a bodies needs beside sources. An example, a flat plate at incidence has been treated. The method gives a good representation of external flow and is suitable for a micro-computer system on its calculation time.

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The personal computer system for analyzing compressible transonic flow and visualizing its flow field has been developed. This system solves two-dimensional Euler equation by using Beam-Warming implicit approximate factorization scheme and the resultant flow field is visualized with computer graphic techniques. This system enables us to save the fare of mainframe computers and promotes the effectiveness in developing the flow code.

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It is very difficult to measure and analyze the internal flows of torque converters because of their complicated construction.
In this report, an attempt is made to calculate the characteristics of torque converters by the combination of an angular momentum theory and a discrete vortex method.
The computed results agree more with the experimental results than in the case of the pure angular momentum theory. It shows us that the present method can be useful as a rational design procedure.

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In this paper, we would like to explain the visualization system for surface pressure using electronically scanned pressure sensors. This system is able to measure 512 pressure sensor channels (32 sets of 16-port module) simultaneously in which the maximum sampling frequency is about 330HZ. We carried out a wind tunnel test about bluff bodies in various aspect ratio, and we created a 16mm movie to visualize the fluctuating surface pressure(aspect ratio=3) using 3D computer graphic techniqes. So we can observes a interesting phenomena of strong negative pressure patern movement on side of the bluff body.

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The pulse-laser induced luminescence method (LIL method) developed in our laboratory has proved promissing for instantaneous quantitative measurement of flow velocity distribution. Now luminescent particles with small diameter can be obtained and the LIL method is applicable to gas and liquid flows. However, the CRT images have small line width and intensity distribution because the luminescent images are exposured on the CRT camera through a hole of a rotating disk as a shutter.
In this study, to obtain thin time-lines from the CRT images, image processing methods are investigated. A frame memory is used for recording, and a personal computer, for processing. The meth-ods with Sobel filtering and thinning, and with thresholding and thinning are suitable for the processing.
Using these methods, variations of time-lines in a T branch tube are observed.

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This paper reports on an experimental study and flow visualization in the counter-flow type vortex tube. The flow visualization is performed by means of liquid injection. The liquid used is water or ethyl alchol dyed by a fluorescein.
The obtaind results are summarized as follows:
1) In the case of using water helix line is observed on the wall because of the condensability of water.
2) In the case of using ethyl alchol the right helicoid and Gortler vortices are observed on the wall.
3) A rotating ring is found near the stagnation point.
4) The inner flow except the axial flow is almost a spiral flow in the plane which the free vortex and the source flow are combined.

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An experimental study on dynamic behavior of a thermal stratification in a tank was carried out. The temperature and flow fields were visualized by using the liquid crystal tracer, and the dynamic phenomena of the thermal stratification and the thermal plumes were recorded by VTR. When the upper wall was cooled rapidly, the cold plumes formed in the vicinity of the upper wall, moved downward and finally emerged into the thermal stratification. The liquid was well mixed by the cold plumes, and the thermal stratification disappeared.

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Two new methods of liquid-crystal thermometry are developed to determine 2-dimensional temperature distributions, excluding human color sensation as quantitative measure of temperature. First method uses interference type optical filters having very narrow band of transmittance to take out an equi-color region selectively. Applying image processing technique, as many iso-therms as used filters can be drawn. Second method uses color-separation optical filters to obtain tristimulus distributions of the liquid-crystal surfaces and correlate temperature and tristimulus using multiple regression analysis. Three applications are carried out to visualize complicated temperature distributions on distrubed heat transfer surfaces and to demonstrate effectiveness of present methods.

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A fluid flow mapper is used as the equipment to visualize and simulate the two or three dimensional potential fields. The fluid flow mapper consists mainly of a glass and plaster plates which constitute a thin channel, and a stationary potential flow appears in the channel. A potential flow is subject to the influence of the pressure and velocity of the fluid in a narrow space. Stream lines of the potential flow are visualized by a methylene blue in the water. This paper analyze an electric field at the boundary in the complex dielectrics of the parallel plate electrodes system by the fluid mapper. Equi-potential lines are formed from the flow lines by a circle-in method. The results agree with the numerical values by culculations of a computer. Accordingly, it can be understood that flow patterns from the fluid flow mapper show electric force lines. This method has the great advantages that potential fields can be observed continuously and results of the numerical calculation by the computer can be inspected. Moreover, this method is very useful to analyze Laplace and Poisson fields in the multi-dielectrics substances.

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The excitation of the air column within a tube closed one end, placed in a uniform flow, was first presented by Vrebalovich. The air column oscillation was produced by means of mounting a tripping device, e.g., a ring or a wedge, at the front of the open end of the tube.. However, the resonable explanation about the oscillation mechanism of this resonator was not given by the author.
In order to get a better understanding of the oscillation mechanism of the resonator with a wedge as a tripping device, the wedge wake coupling with the oscillating flow produced within the resonator is visualized by means of the hydrauric analogy using an open channel of water. The shadowgraph method-is applied to the observation of periodical flow, and the speckle method is applied to the quantitative visualisation of flow pattern at any instant.
The results of flow visualization give well understanding of flow structure produced by periodic vortex-shedding from the wedge coupling with the resonator.
(1) T. Vrebalovich, Jot Prop. Labo. TR-32-378(1962)

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In recent years, computational fluid dynamics and computer graphics have become important and useful to visualize three-dimensional wake structures. This paper shows the flow around a one-box vehicle, which is calculated with a third-order-upwind scheme. A CRAY X/MP12 was used for the computation and an IRIS3130, graphic workstation, for the visualization.
Computational results were visualized by stream lines and time lines, which show the wake structure clearly. It is concluded that the third-order-upwind scheme is effective for the flow analysis around the vehicle and that the graphic workstation helps us easily understand the flow field.

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In this paper several time-dependent flow problems are computed by the finite element method, and the results are visualized by the automatic animation production system which is made up of a personal computer and a home video recorder.

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The present paper deals with the two-dimensional and threedimesnional flow fields within automobile passenger compartments. They are studied by solving the incompressible Navier-Stokes equations numerically. The computational procedure employs a 3rdorder upwind scheme which has been proved to be very effective for the analysis of high-Reynolds-number flows. Furthermore, the Boussinesq approximation is employed because the present cases treat flows with small temperature difference.
The output of the computation is introduced into an en gineering work station, and displayed using color graphics or animations. It is shown that the computed results for twodimensional velocity fields are in good agreement with the twodimensional experimantal data. As far as the temperature fields are concerned it seems that heat transfer is generated by vortex convection.

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Computer-aided vorticity measuring system based on hotwire anemometry has been developed and used for investigation of time-dependent vortical flow field of a traveling vortex ring. The vorticity distributions obtained are visualized on computer graphics and are recorded as animation film. Instantaneous vorticity contours measured are compared with Schlieren photographs taken at the correspponding time instant. This system is applicable for research of various vortical flow field.

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It is investigated to predict heat transfer and to visualize air flows around a cylinder and a single row of cylinders. Direct numerical simulation of Boussinesq approximated NavierStokes equation is carried, and upwind finite defference method with third order accuracy is used. Generalized cordinate system is adopted to give flexibility on treating objects to calculate.
The results of calculations are visualized on a computer graphic display and made into animations. The results are successfully coincident with experiments, and some visualizations of the air flows are shown in this report.

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This paper describes a new method of the visualization of the complex high speed flows contain shock waves, expansion waves, contact surfaces and shear layers. This method is based on the streamwise density gradient, then the authors call "streamwise schlieren method". The algorisms of the visualization are explained, and an example of the visualization of the shock diffraction from a convex corner is showed.

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This paper deals with a numerical simulation of the flow with some narrow passages in the rectangular pipe. Namely, a numerical analysis and the flow visualization for the narrow passage flow which is formed by setting up some protruding parts in pipe were studied for ten numbers of models. And a study on the various effects of the height, distance, and width of a protruding part and a location of outlet was done in detail. In this investigation, a numerical calculation and the flow visualization were carried out for Reynolds numbers ranging from 1 to 700. As a result, a numerical calculation obtained was in close agreement with the flow visualization, thus the narrow passage flow with some protruding parts in rectangular pipe were clarified.

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Three-dimensional visualized flow analysis of unsteady flow structure was quantitatively carried out by means of personal computer with image processing system. Images of the flow field visualized with dye are three-dimensionally captured by CCD camera and stroboscope.
Time sequences of digitized images of stroboscope are stored in computer memory using a memory board and are analyzed successively. This system is able to prepare larger amount of time sequential data than a usual camera system does. The system is applied to study turbulence transition of three-dimensional pipe flow.

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A technique for measuring the three components of velocity in liquid flows is developed by using a digital image processing system. This system consists of two Coupled Charged Device (CCD) cameras, a digital image processor interfaced with a micro-computer, and a stroboscope triggered by the CCD camera. Based on stereoscopic photography theory, the instantaneous three dimensional position of a tracer in a liquid flow is calculated by the relation between absolute and image coordinate systems, which is established by camera calibration. The present algorithm is verified by a preliminary experiment using a rotating solid model, and the associated uncertainty is evaluated systematically. An unsteady laminar Couette flow between two concentric cylinders, of which the outer cylinder starts to rotate impulsively, is measured by the present technique. Good agreement between the experimental and numerical results of instantaneous velocity distributions demonstrates the validity of the present technique for the application to the measurement in unsteady three-dimensional shear flows.

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A real-time velocity measurment system based on the digital image processing approach has been developed for analyzing the twodimensional flow field. Water flow around a circuler cylinder is visualized by nylon beads and instantaneous particle images are recorded by TV camera, consecutively. The velocity data are extracted automatically through our system.

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New application of visualization technique by electrolysis method is proposed here. Usually the cathode or the generator of tracer is a metal rod in existing studies, while in the present study the small parts of the model-surface are numerous cathode-dots which are the uncovered spots surrounding by painted and insulated surface. The principle of the present technique exists on that the electrolysis of phenole-phthalein is possible only on these uncovered 'spots'. The model used has the surface curve of the axisymmetric paraboloid. Clear images of separation line were obtained at wide range of angle of attack of the paraboloid. The present technique also has the following two advantages. First the dots can be shifted after repainting of the model. Second, if we apply large voltage the hydrogen bubble can be generated enough for them to accumulate to make a series of tracer and useful for visualization of vortical flow around a model.

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In the previous papers, an image processing system using correlation technique was developed to obtain the instantaneous velocity vector distributions in a two-dimensional flow field. In this system, the spatial resolution of the velocity vectors becomes worse as pixel matrix dimensions for correlation increase. On the other hand, the erroneous velocity vectors increase with decreasing the pixel matrix dimensions.
In this study, the correction of erroneous velocity vectors is attempted in order to decrease the erroneous ones in the smaller pixel matrix dimensions. The procedure is as follows. 1) The erroneous velocity vectors are eliminated. 2) The newly estimated velocity vectors are adopted in place of the erroneous ones.
Furthermore, the rotation of the matrices is also applied to the calculation of correlation to decrease the erroneous vectors.
The following facts are specifically confirmed;
1) The velocity vector distributions can be obtained by using the smaller pixel matrix.
2) The rotation of the matrices can be neglected so long as the matrix dimensions are sufficiently small in comparison with the flow field ones.

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A method to measure two dimensional velocity distribution by analyzing VTR images of visualized flow and examples of its application are presented. In this system, (1) flow is visualized by tracer particles, (2) particle images in consecutive frames are traced and (3) inadequately traced data are eliminated based on the criteria of (a) difference between particle image areas, (b) magnitude of particle acceleration or deceleration and (c) difference of velocity vector from surroundings.
The estimation error of particle image displacement determined by using a turn table was within one pixcel in most case.

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A method to measure three dimensional velocity distribution by analyzing VTR images of visualized flow and examples of its application are presented. In this system, (1) flow is visualized by tracer particles, (2) particle images in consecutive frames recorded by two TV cameras stereoscopically are independently traced and (3) composed by stereo pair matching to calculate three dimensional velocity.
No special device to control camera positions and thier axes is necessary in this system because camera parameters are calculated from four landmarks placed in a flow.

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It is necessary to establish measures to prevent back discharge and to design an economical electrostatic precipitator (ESP) for flyash particle collection in coal burning electric power stations.
Under these circumstances, it is necessary to analyze fine flyash particle motion in an ESP for each particle diameter within a range of one micron.
The motion of charged flyash particle is influenced by Coulomb force and by viscosity force in an ESP. Flyash particle motion is therefore analyzed based on electro-hydro-dynamics. This paper describes the flyash particle trajectories observed using a visualization technique and the computed simulation results.

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New high voltage high frequency pulse generator for flow visualization was developed. This divice has a high voltage high speed switching circuit and can produce very sharp and high frequency pulses. The pulse width is 0.5-1 ?? s, and maximum output voltage and frequency are 250kV and 100kHz respectively. So, wide velocity range from low velocity about 1m/s to super sonic flow can be measured using this device. Some visualized examples are shown in this paper.

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The preliminary visualization technique for a low density gas flow is discussed. The optical absorption phenomena of ultraviolet ray by ozone are applied. Ozone has a region of continuous absorption between 2000A and 3000A of an ultraviolet light wave length, with a noximium at 2537A. Therefore, the parallel ultraviolet light from a low pressure mercury lamp is injected from one side wall of a test section. In the reduced pressure test section, oxygen-ozone mixture jets are forced into from a nozzle. The ultraviolet light passing through the jets are absorpted. The radiation emerging, after absorption in the jets is transformed into visible light by fluorescent screen.

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The vapor-screen method, a simple and practical method of flow visualization for high speeds, has been applied to shock wave. As the result, the condition and problems of visualization have been clarified and it has been demonstrated that this method is very useful to visualize shock wave.

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Structures of interacting Ar free jets of are studied by the flow visualization. The experiments are carried out for various angles between the jet axes, from θ=45° to 180°, and various ratios of the source pressure Ps to the pressure of the expansion chamber Pb. For flow visualization, laser indused fluorescence of I ₂ seeded in Ar as a tracer is employed. Structures of interacting free jets considerably depend on θ and Ps/Pb. In the condition of up to θ=90°, the flow field represents symmetrical structure with respect to the interacting plane which bisects the jet axes. As θ increases further, the flow field represents the complicatedly three dimensional structure and has many types of structures depending on Ps/Pb. The most characteristically three dimensional structure in this paper is φ-structure for below θ=90° which named after its geometrical similarity of the cross section to the Greek letter φ. Far downstream, the φ-structure tends to be planar in the interacting plane.

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Visualization and quantitative measurements of the velocity field of a laminar water flow through a branch tube of square cross section was made using a laser induced fluorescence (phosphorescence) method (LIP). Velocity profiles in two directions across the tube were visualized in totally 23 different cross sections located at the upper and lower streams of the branch portion along the flow direction. The wall shearing stress was obtained from these visualized velocity profiles and the map of the wall shearing stress over the whole flow field was obtained.

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In designing spool valves which are widely used in hydraulic power applications, one of the most important problems is to estimate and reduce the axial force acting on the spool of the valve. This axial force can easily be estimated from momentum theory if the behavior of the jet issuing from the metering orifice of the spool valve is expected.
In the present paper, a three-dimensional model of the spool valve has been designed to observe the flow near the metering orifice. This model is made of transparent acrylic resins. The jet issuing from the metering orifice is visualized by a tuft method. The images of flow fields recorded by CCD camera are fed into a microcomputer and an digital image processing is employed to investigate the behavior of the jet.

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The effect of periodic two-dimensional excitation on the development of a turbulent mixing region in open-channel parallel coflows was investigated experimentally by making use of visual study and hot-film anemometers. Controlled oscillations of variable frequency were applied at the initiation of mixing between two parallel water flows. When the frequency of the forced oscillations was lower than the fundamental frequency (in the present case it was 1 Hz) which might describe the interaction of vortices, i.e. pairing, the spreading rate of flow was increased by enhancing the coalescence of neighbouring eddies. On the other hand, at the frequency higher than the fundamental one, the controlled and resonant vortices were generated in a single array of large vortices, which did not interact with each other. Consequently, the spreading rate of flow was depressed, and also the Reynolds stress became negative.

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