A vortex growth in two-dimensional jet flow is numerically analysed by solving full Navier-Stokes equations. For the symmetrical disturbance induced by computational errors, the flow field takes unique vortex passage frequency which is dominantly amplified disturbance frequency. Several asymmetrical disturbances with this frequency and different amplitudes are applied at IN-boundary to get asymmetrical vortex array. In the case of disturbance with maximum amplitude 1 percent of the inlet velocity, the array of vortices shows the asymmetry in early stage and persists in the computational domain. For 0.5 percent amplitude, the coalesced vortices are simulated after a large time elapses. This phenomenum may be triggered by lateral displacements of vortices. which imply that each vortex travels downstream with different speed. In the coalescing process, two vortices rotate each other, and one of vortices is outer vortex downstream of the other which is inner vortex. The traveling speed of outer vortex becomes low, so two vortices draw near and coalesce.

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The motion of small particles in a turbulent jet is visualized by calculating the trajectories of particles in an instantaneous flow field simulated using an axisymmetric discrete vortex method. The jet is issued into the ambient air with the velocity of 37.5m/s from a convergent nozzle with a exit diameter of 20mm. The instantaneous distributions of particle are calculated for three different size of DOP particle of 1μm, 10μm and 100μm in diameter, which fidelity to the flow is good, medium and very poor in order.
The results of particle dispersion calculation show that the motion of all the size of particles calculated is controlled strongly by large scale vortex structure of the jet. The interesting phenomena that the relatively large particles disperse to far out of the jet and that the dispersion of particles is enhanced abruptly at a certain location of the downstream in the jet are attributed to the large scale vortex structure of the jet.

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Two-dimensional iodine concentration in cold jets were visualized by the planar laser-induced fluorescence method. The laser sheet was formed by multi-reflected laser light, and a correction method of the heterogeneous laser sheet was developed. Average concentration in a cold nitrogen jet was measured at a velocity of 18.9 m/s. The two-dimensional distrubution profile of the average concentration showed familiar jet profile. The transition to the fully developed region was recognized by the longitudinal decrease of the peak concentration. The concentration profiles at different locations showed self-similarities. Unsteady confined helium jet was also visualized at a rate of 100 frames/s and showed the behavior of the injected jet and its mixing process.

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Recently, water jet is intensively used in the mechanical engineering and medical application as well. However, the structure and movement of the high speed water jet itself are not clear cut yet.
This paper is mainly concerned, by using double exposure holographic interferometry, with the structure and velocity decay of high speed water jet. Experiments were conducted In an Aqua-Jet-Cutter at injection pressure about 230MPa, and with a 0.25mm diameter nozzle. It is found that the water jet velocity is estimated by measuring the angle of the Mach line generated around the jet.

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The behavior of the horseshoe vortex and the wake vortex around a square plate standing vertically on the flat plate where the laminar boundary layer was developing was examined by visualization technique. The pattern of the wake vortex could be classified into three group according. to both the Reynolds number Reh and the plate height to boundary layer thickness h/δ in the range of Re _h<3700 and h/δ<3. The horseshoe vortex around the square plate showed the characteristic behavior corresponding with the pattern of the wake vortex respectively.

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The flowfield produced by a vortex pair approaching a circular cylinder was investigated, firstly, by smoke visualization technique. Our attention was paid on the velocity profiles in the separated region on the cylinder where the secondary vortex is formed. It was found that Taneda's criterion must be carefully applied to the determination of the unsteady separation point from the integrated streak which was initially ejected from a nozzle.
Next, numerical calculations were performed by both direct calculation of Navier-Stokes'equations and a discrete vortex method. The tertiary vortex observed by the smoke visualization was also obtained by the numerical calculations; its generation could be reasonably explained from the velocity profiles.

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The flow around a bluff body which starts near a plane wall at low Reynolds numbers of 150 to 500 has been investigated. The drag and lift forces were measured and the corresponding flow patterns were visualized by the electrolytic precipitation method in a towing water tank, to examine the effects of and the gap-to-height ratio S/H and the width-to-height ratio B/H of a cross section of the cylinder. We find that a suction force forward to the wall is exerted on the cylinder with the B/H ratio of 0.6 and 1, and that the critical value of the gap ratio is estimated to be about 0.5; At the gap ratios S/H over 0.5, a regular vortex street can be observed and at narrower gaps than 0.5, a vortex street breaks down. There is a good correspondence between the results of measurement of lift force and flow pattern.

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Weis-Fogh suggested a model of insect flight, a new mechanism for generating circulation (so called 'Weis-Fogh mechanism') . During the 'fling' (opening*) stage in Weis-Fogh mechanism, a pair of wings opens by rotation about a common edge. In this papaer, the experimental and the analytical studies are conducted and the following is obtained. When clearance exists between two wings, the flow around the plates becomes completely different from the flow without any clearance. This causes the significant difference of the circulations around the plates.

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In a particle tracking method, a few percentages of errors are included. In order to process them, two kinds of indices, which enable the quantitative evaluation of estimated pairs are newly difined in this paper. The effectiveness of these indices showed in measurment examples. And it is confirmed that these indices are useful to expand the applicabilities of the binary image correlation method, and measure velocity distributions efficiently and automatically.

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A new technique of the frequency measurement, which is based on the digital image processing, has been developed for shedding vortices from a circular cylinder. The vortex motion behind a circular cylinder and the main flow motion in front of a circular cylinder are visualized by a dye injection method of fluorescent and a direct injection method of tracer particles. In the present technique, the shedding frequency of vortex and main flow velocity are both measured on the digital images. Visualized vortices in consecutive TV images are analyzed by Correlation Method and/or Density Averaging Method. The shedding frequency can be determined as the density pattern change caused by the, dyed vortices through a measurement region behind a circular cylinder. Using the present technique, St numbers at range of Re number 50 to 200 are measured automatically and quantitatively.

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A new concept of the pictures for the particle tracking method is introduced, and it is applied to estimation of the optimum size of correlation area. The estimation is found to be adequate for two different examples. A fast algorithm for rotating pattern matching method are developed, and the algorithm enforce the perfornance of the correlation method.

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A visualization system was newly developed to analize computational and experimental results of fluid dynamics. The system was used to analize formation of gas motion in engine cylinder and air flow behavior around a vehicle. This paper describes the structure and the characteristic function of hardware (ex. computational structure, network, data flow) and original software system with sample results.

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The performance of a system which determine 3D velocity distribution using particle-tracking method, through image processing of visualized image recorded with two TV cameras, are discussed. In the system, after determining camera parameters from a landmark image, 2D vectors are identified in each camera image using particle-tracking method, and 3D vectors are reconstructed through stereo- pair-matching. It is shown experimentally that position estimation error projected on screen coordinate was about one pixel. Estimation error of 3D position was analyzed as a function of 2D error, angle between camera axes, etc. The performance of stereo-pair-matching was analyzed as a function of 2D error, angle between camera axes and tracer concentration. It is shown also experimentally that error in velocity measurement is within tolerance.

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The purpose is to exactly determine a flow state of a thermal plume bymeasurement and analysis of plume spectrum, The behavior of even a laminar plumeis always time-dependent, because the laminar plume sways naturally. Atime-dependent temperature of the thermal plume is measured on the mid-plane, onthe several given height and to the axial direction of the heated wire. Thepower spectrum density (PSD) is obtained from time series data of plumetemperature by the maximum entropy method (MEM). By a criterion of the PSDgradient, a flow state, viz. laminar, transitional or turbulent, in the thermalplume can be quantitatively and exactly determined on the mid-plane, on theseveral given height and to the axial direction of the heated wire. Thiscrieterion for determination of flow state can be applied to any kind of flow.

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Holography is a recording and reconstructing method. Holography theory can be applied to control the wave height in coastal engineering. The process has two steps. The first is the synthesis of holograms by the computer holography method. The second is to make up this hologram to the slit structure in coast.

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The surface of insulators accumulates charge during subject to high voltage stresses electrically.The surface charging causes deteriorations of electrical performance and durability of high voltage insulators in gas. In this paper, we describe a result of visual analysis of electric fields with accumulation charge on complex insulator surface to clear the effect of surface charging on the dielectric strength. Moreover, the accumulated surface charge on insulators is estimated by flow patterns obtained from axisymmetric three dimensional fluid flow mappers with fixed sand-bed.

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A fluid flow mapper is a visual equipment of electric flux for analyzing electric fields. In this paper, we propose a visualization method of equi-potential lines by using an inversible fluid flow mapper. The inversible fluid flow mapper is based on a fact that streamline and equi-potential line equations of the fluid flow mapper can be exchanged inversely. This method has the advantage of being able to visualize equi-potential lines very easily instead of numerical calculation methods by computer. Therefore, it is concluded that this new method improves the value of fluid flow mappers for electric field analysis.

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The vapor-screen method, a simple and practical method of flow visualization for high speeds, has been applied to supersonic flow field generated in an indraft supersonic nozzle. As the result, the condition of visualization has been clarified and it has been demonstrated that this method is very useful to visualize flows in the indraft tunnel.

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Free-jets issuing from a circular, square, rectangular with different values of aspect ratio, and a regular triangle orifices are visualized by means of a laser-induced fluorescent method. It is shown that for the circular orifice, axisymmetiy is collapsed by increasing the stagnation pressure. For the square orifice the cross section of the jet becomes also square, but the side inclines 45 degree to the side of the orifice. For the rectangular orifice the shape of the cross section becomes rhomb and the direction of the longer diagonal is in direction of the orifice width. The longer diagonal becomes longer than the other with increasing the aspect ratio of the orifice. The distance of the normal shock on the jet-axis increases with square root of the pressure ratio between the stagnation and the ambient pressures and the proportionality constant is about the same as for a circular orifice. It increases almost with square root of the aspect ratio. For the regular triangle orifice the side of the cross section is orthogonal to the line connecting the apex of the slit and the center. Radially expanded jets due to the strong interaction of shocks were observed for all orifices presently tested.

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Computational studies of focusing process of shock waves reflected from a parabolically concave reflectors were performed and the results were visualized by a computer movie system using a personal computer and a video converter device. The computations were carried out by solving the two-dimensional Euler equations by means of the piecewise-linear-metod. For the purpose of making computational visualization, the Laplacian of density were calculated at all the grid points, and then the computer shadowgraphs were developed based on the principle of optical shadowgraph.

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Converging shock waves were visualized by optical shadowgraph technique. The converging shock waves were generated by reflecting an initially plane shock wave from a parabolically concave wall and thereby the behavior of the converging reflected shock wave could be well understood. The experment was carried out in a conventional shock tube with air as driver and driven gases and measured shock Mach number was 1.13. Thus optically visualized shock waves were compared with the computer shadowgraphs of computed focusing shock shape and fairly good agreement was obtained.

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When the effects of viscosity is dominant in the peristaltic pumping, the normalized pressure rise at zero time-mean flow is independent of Reynolds number. The pressure rise increases nonlinearly with Reynolds number at high value of it caused by the inertial effects. The experimental results indicates that the critical range of Reynolds number separating both tendency is about 1020.
In this report, the flow patterns in the region are experimentally analyzed by means of flow visualization. The method is the speckle photography illuminated by laser-beam-sweeps which not only gives images of flow patter, but two-dimensional velocity distributions. The results of visualization give clear understanding of the change of pressure rise tendency in the region. The flow pattern drastically changes as the Reynolds number exceeds 10. The vortex street developed from two shear layers bounding reverse flow generated in the convergent region of the peristaltic wave appears.

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In this paper, the flow of a counter flow type vortex tube is visualized. The flow visualization is performed by means of the tuft stick method. The tuft dyed with fluorescent dyes is used and the length of the tuft is changed from 5mm to 20mm at intervals of 5mm.
The obtained results are summarized as follows;
1) It is considered that, except for near the wall, the tuft with 5mm length only shows the direction of flow but does not show the actual inner flow because of the stiffness of a thread.
2) If the tuft with over 10mm assumes to show a phenomenon close to the real inner flow, it will be supposed that those tufts present a secondary flow in the vortex tube.

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A experimental study on an extended flame and its behavior issued from an opening was conducted using a model compartment. A rectangular diffusion burner was adopted as a model fire source, and was set at the end wall in the compartment. The three different flow rate of propane gas of 30, 40 and 60 1/min were employed. We changed the opening area as full opening and 1/3 opening. The effects of pent-roof and fascia on the length of extended flame were also tested. The temperatures along the vertical wall during a fully developed fire were visualized using an infrared image processor and were also measured by means of thermocouples. The temperature contour maps were made based on both temperature data, and their crose correlation was elucidated.

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A discrete vortex model is introduced in the calculation of the starting flows around a two-dimensional elliptic airfoil oscillating in pitch at large incidences. The potential flow past an obstacle is represented by a fixed number of bound vortices distributed along the airfoil surface and the viscous wake by an increasing number of free vortices, which are shed from the leading and trailing edges with a regular time interval and convected downstream under the action of the free stream velocity and the vortex-induced velocity. Every time stage of the calculated wake is visualized by means of point vortex plots and of streamline tracings. Some comparison is made with the streamline profiles originating from the visualization experiment.

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In order to improve vehicle aerodynamics, it is essential that the effect of air flow behabiour on aerodynamic forces be clarified. To this end, air flow around simple bodies was visualized by means of laser sheets and the velocities and pressures mapped using a 5-hole probe. From analyses of the results, it was established that drag is mainly affected by the distribution of air flow velocities at a particular cross-section. The visualization and mapping technique is therefore thought to be a useful design tool.

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ASKA adopts an Upper Surface Blowing scheme as a powered lift system. This depends on Coanda effect of flow over curved wall surface. A typical vortex generator configuration has been introduced in flight tests and their supporting tests. Other interesting devices such as small vortex generators and side fences have also been developed. Recently all these Coanda devices have been examined, compared to the case of no device, in ASKA's ground tests. The report concerns indirect flow visualization by wall temperature measurements of main wings, flaps and a fuselage exposed to engine exit flow.

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The biplane axial turbine with setting angle has been manufactured and tested to investigate the effects of setting angle, gap to chord ratio, and arrangement of biplane rotor on the turbine performance. The results have been compared with those of the biplane Wells turbine. A suitable choice of the design factors has been suggested. Next, the hysteretic characteristics has been clarified from the viewpoint of the design method. The hysteresis is more sensitive to the arrangement of biplane rotor and less sensitive to the setting angle and gap to chord ratio. By means of flow visualization, the relation between the overall characteristics and the behavior of wakes has been discussed.

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Usually, as the cause of downwash of stack plume, it is said that separation flow from the side of a stack generates negative pressure zone behind it, and the negative pressure zone draws plume. But when a stack has an outer facing, it seems that leading edge separation from the top is more dominant for downwash.
To clarify the effect of interaction between leading edge separation and plume, flow patterns around a stack which has two ducts and an elliptical outer facing are observed in the wind tunnel. Measurement of temperature distribution is also carried out with thermocouples. It is clarified that separation vorticies from leading edge of the top of stack also draw plume in the process of downwash.

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Temperature distribution and flow pattern of natural convection around IC packages on the vertical circuit board in silicone oil were made visiable with the liquid crystal particle suspension method. Natural convection around IC packages were affected by the array of IC packages on the vertical board. Thermal boundary laye and thermal plume around IC packages were made clearly observation. The difference in temperature of the surface of IC packages and the mean value of oil decreased with increasing the horizontal distance of the upper and under IC packages.

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In this study, the drag of club heads were measured that was related to ease of swing and maximum head speed, where as club heads were studied in the past only in their material, construction, hardness and rebound. The drag of several shape of club heads were measured at flow speed of 20 to 50 m/s conceded from law of fluid mechanics. And, the flow around club head was made clear by the flow visualization results by using spark tracing method.

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The unsteady notion of a sphere in still and viscous fluid under the gravity is experimentally studied using the flow visualization techniques. The locations of the sphere were measured by stroboscope flash and some of the fundamental features were elucidated by these experiments.

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Tracer methods have been frequently applied to know flow patterns in flow visualization technique.
Recently, they have been applied not only to know qualitative flow patterns, but also to know some flow quantities through the measurements of tracer velocities under the remarkable development of computers and image processing techniques in a decade. In this stage, it becomes important to know the response of a tracer particle to rapid change of flow velocity like as in turbulent flow.
The step response of a tracer particle is discussed analytically in this paper, by the use of Tchen's equation of motion, including the Basset history term which has the important role in high rate acceleration.

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