The evolving process of a turbulent spot and the flow pattern downstream of a trlp wire are visualized in a transitional plane Poiseuille flow. The fluids studied are water and polymer solutions. The polymer solutions (Polyacrylamide aq.) are viscoelastic liquids and exhibit turbulent drag reduction. The visualized results show that the polymer solutins have the lower critical Reynolds number to two-dimensional disturbances but are more stable to three-dimensional disturbances relative to Newtonian fluids.

抄録全体を表示

At the fundamental studys of the three dimensional tuburent structure, visualization technique by dye injection methord were used. Experiment have done inrectanguler open channel for various aspect ratio (B/H=2, 1, 1/2). There are two cases of channel conditions, one is a smooth serface and other have a roughnessbed. In oder to visualize the turburent structure, water with FLUORESCEIN SEDIUM (Uranin, C₂₀H₁₀O₅N_a2) and vertical (or horizontal) slice of light were used. In this paper reration between turburent structure and mechanism of scondary flow are decribed.

抄録全体を表示

Using a flow visualization technique and LDV method, interfacial phenomena of the exchange flow in a rectanguler tube tilting from the horizontal have been investigated. Thorpe's spiral vortices was observed for the two layer flow having comparatively large density difference. However, to occur in a steady exchange flow was hard to observe. Through the viscous linear stability theory, it was clarified that the reason why the latter waves had never been observed was based on their extremely small growth rates.

抄録全体を表示

Unsteady two-dimentional natural convection of air is studied, which is caused in a holizontal circular cylinder when the pressure in it is decreased stepwis The air velocity at the center of the cylinder is measured by laser Doppler velocimeter and the flow pattern on a cross section perpendicular to the cylinder axis is visualized by tracer method. The natural convection flow has been known to grow at first and then die down gradually for low Gr number, but to oscilate two or three times for high Gr. In the Gr range of 10 ³-8×10 ⁵ the flow pattern is symmetric and no turbulent flow appears.

抄録全体を表示

It is well-known that periodic large suface-eddies are generated at the interface between the main channel and the floodplain in the overbank flow of a composite channel. In this paper. the 3-dimensional structure of the flow in the interfacial zone was observed by hydrogen bubble method. using a closed channel.
It is shown that. accompanied by the 2-dimensional large eddies. there exist inclined eddies rolling like longitusinal vortices near the top-edge of the floodplain. Though the flow pattern is 3-dimensional and very much complicated. it has intense periodicity with the large eddy structure. And it was found that this periodicity can be explained by 2-dimensional stability analysis of a free shear flow.

抄録全体を表示

Structures of weak shock waves reflected from various models in carbon dioxide are observed by using a Mach-Zehnder Interferometer, whose light source is a pulsed nitrogen laser (wave length 337.1 nm). Shock waves of the equilibrium shock Mach number of 1.015-1.097 are generated for initial pressure of about 2 atm in a shock tube of 40×40 mm ² cross section. The observed structures of fully and partly dispersed waves due to vibrational relaxation of carbon dioxide, reflected from a porous wall, a hemicylinder or an inclined plate, exhibit the 'nonstationary effect' and the 'N-wave effect', which are common phenomena for weak waves in dissipative and dispersive media.

抄録全体を表示

The air column in the organ pipe is excited in acoustic oscillations by two-dimensional jets issuing from the flue slit. The large amplitude oscillations of the air column in the Hartmann generator or the Hartmann-Sprenger tube is also produced by air jets issuing from a cylindrical nozzle. The jet-drive mechanism of these oscillations has been investigated by many authors, and now we have reasonable explains for the fundamental mechanism of excitation. However, there is no complete explain on the mechanism of the change of oscillation modes or the transition of linear to non-linear oscillations caused by increasing of jet speed. The visualization results of two-dimensional jets driving the air column in the closed tube obtained in the present paper give useful informations for the analysis on the mechanism of the transition of linear to non-linear oscillations.

抄録全体を表示

The visualization of air flow is often made by the use of oil mist. The mist condenses on the wall of wind tunnel. It is not an easy task to clean up walls of a large wind tunnel. In order to avoid this trouble we have developed a method of visualization by the use of small water droplets. The water vapor produced in a boiling-water container goes through a thick bed of lumps of dry ice (carbon dioxide).
Water mist is injected into the air flow. The dense smoke comparable to conventional oil mist has been obtained. Water droplets eventually vaporize and there is no contamination in wind-tunnel. Another method of visualization has been tried by filling a shallow box with water mist. If we make the mist a little cooler than surrounding atmosphere, the mist settles in the box. This box can be used as a towing tank, namely, various kinds of solid body can be moved in the box and the flow picture is taken. We visualized the flow field around model automobile of various shapes.

抄録全体を表示

Three dimensional flow around a cylinder settled vertically between walls in a parallel channel was studied using pearl pigment as flow visualization additive in water flow. Horseshoe vortex around the cylinder was observed, and a new periodical vortex system was found at high Reynolds number. Downstream the cylinder, alternating vortexes were found, but this vortex shedding Reynolds number was higher by 2 decades than well-known Karman vortex.

抄録全体を表示

The method of speckle phtography is useful for measurement of velocity distritribution of whole flow field. However, the point-by-point measurement of local velocity by means of Young's fringe method takes much time. We discuss a method of automatic measurement in the present paper.
In order to analyze Young's fringes, we use two algorithms, one is FFT and the other is spatial fringe scanning (SFS). In the former, fringe spacing is determined by spatial frequency of first peak of the Fourier spectrum. In the latter, on the other hand, video signals are compared with reference periodic signals. Both of spacing and direction of fringes are determined automatically.

抄録全体を表示

This paper presents flow visualization of free jets from a sonic nozzle by LIF (Laser lnduced Fluorescence) method and an analysis of their structures by picture processing. LlF method in this paper uses a property that iodine, seeded in carrier gas, radiates fluorescence by irradiation of laser beam. Features of free jets, mach disk and barrel shock, are measured from picture processing of developed films.

抄録全体を表示

The structures of the streamwise vortices and transverse vortices in a turbulent spot are investigated using two visualization techniques that utilize fluorescent dye excited by a sheet of laser light (2 watt argon laser).
The results indicate that (1) a number of the streamwise vortices and transverse vortices which have some scales, exist in the turbulent spot, (2) small scale transverse vortex exists at the top of the stream-wise vortex, (3) large scale transverse vortices are formed at the rear region of the turbulent spot, and (4) low speed streak exists in the root of a pair of the counterrotating streamwise vortices near the wall.

抄録全体を表示

It is difficult to visualize the details of turbulent air flow structures by traditional visualization systems. In order to visualize the detailed characteristics of turbulent air flow, a new system using a laser light sheet has been worked out. This system can clearly visualize details of the turbulent air flow around buildings and contaminant diffusion process from the stack of a building. The source of the light sheet is an Argon ion laser(4W), which is set on the traversing unit. The high power laser beam is changed into a light sheet by traversable cylindrical lens or optical fiber cable with cylindrical lens system. Magnesium carbonate (MgCO ?? ) powder is used as the particle tracer. The results are as follows. (1) Through this system, it is possible to take photograph which clarify the fine structure of eddies in turbulent air flow. (2) It is also possible to visualized the details of the contaminant diffusion process from the stack of a building.

抄録全体を表示

An open channel flow is three dimensional because of a coherent motion which is originated in a bursting phenomenon or a depth-scale longitudinal eddy. In this paper the three dimensional turbulent structure of these phenomena were investigated by a flow visualization technique. A tracer method was used to visualize a flow in a cross section, a horizontal section and a vertical section. Neutral tracers were illuminated by a laser light sheet which was obtained from a 5 mW He-Ne gas laser. A video camera and a 35 mm still camera were used in a moving shot or a fixed shot, and many attractive pictures were obtained. To visualize a flow in a cross section, a bore scope shown in Fig. l was used with a image intensifier. Based on these results, the three dimensional turbulent structure of an opn channel flow was illustrated.

抄録全体を表示

Coherent structures in the outer layer of turbulent channel flow are investigated using a visualization technique that utilizes fluorescent dye excited by a sheet of laser light (2 watt argon laser).
The results indicate that large scale ejection in the outer layer is formed by which some streamwise vortices in the near-wall region collect and develop away from the wall, and induces the boil near the water surface. Further studies suggest that the large scale transverse vortex exists in the outer laver. It is not clear of the corelation between the transverse vortex and the streamwise vortices in the near-wall region.

抄録全体を表示

In laminar flow type clean room. an air flow is disturbed by apparatus and operators
It is required urgently to clarify the turbulence characteristic around them. A scale model of laminar flow typ e clean room was used to visualize the air flow pattern within it. A laser light sheet and fine magunesium carbonate powder were adopted as the light source and the particle tracer respectively. Scattering light of tracer particles was taken into picture and the turbulent flow was analyzed. Various dimensions of rectangular prism models were used as symplified apparatus. By changing the arrangement of these apparatus in the model room, the basic design data were obtained. those were useful for predicting and controlling the contamination distribution in laminar flow type clean rooms.

抄録全体を表示

For a full tanker ship model running with a constant drift angle, oil film method and dye tracer method of flow visualization technique were applied to the observation of separation vortices, streamlines near the ship hull and limiting streamlines on the hull surface. Comparing these results with measured pressure distribution on the hull and vorticity distribution in the wake flow, a lot of information about the flow field obtained by tank experiment was confirmed to have consistence each other. For example, position of 3-D separation lines and directions of surface streamlines correspond well to the peak and gradient of pressure distribution respectively. It is shown that flow visualezation techniques are quite useful to investigate not only the flow field structure but also the ship motion, because separation of flow, initiation and behavior of vortices are keys to understand the wake flow and hydrodynamic force acting on the ship in maneuvering motion.

抄録全体を表示

Wells turbine can rotate in the same direction even in the reciprocating air flow produced by the oscillating water column inside of the air chamber which is fixed at the sea surface. It means that Wells turbines have self-rectifying characteristics and make the total wave power system simple.
Although the Wells turbine is simple, the turbine produces the complicated flow field with the distinctive blades. In order to understand the flow, we visualized it. The performance tests were done in the wind tunnel, and the flow patern on Wells turbine blades were visualized by using the oil film method in the water tunnel. The influence of sweep angle was explained by these experiments.

抄録全体を表示

When a car runs at high speed, "wind noise" is generated. It is said that the vortex behind the A-pillar of the car is strongly correlated with the generation of the wind noise.
A flow visualization method has been developed. A laser light sheet and soap bubbles are used as the light source and the tracers, respectively. The flow field around the A-pillar of a 1/5 scale car model is visualized by this method.
As a result, it is seen that the shape of the vortex varies as the yaw angle or the A-pillar shape changes. Furthermore, the correlation between the shape of the vortex and the wind noise level measured in the passenger compartment is investigated.

抄録全体を表示

To understand the striking difference in heat release rate between the vertical and horizontal torch nozzle in a prechamber spark ignition engine, the torch flow patterns remained on the piston and both the valves heads are visualized by the oil-film technique, changing the number, sectional area and direction of torch nozzle, respectively.
As a result, the jet velocity of torch nozzle is confirmed to decrease proportionally as the nozzle increases in diameter or number. Furthermore, it is revealed that combustion in the main chamber with vertical torch nozzle is accelerated by strong turbulence due to the torch jet impingement, and then it shows not only a sharp peak in heat release rate, but also earlier completion in combustion than that of horizontal torch nozzle.

抄録全体を表示

To make clear the behavior of swirling flow induced into cylinder of a motored model engine with high swirl port, the pattern and direction of air flow in the cylinder are visualized at every crank angle during intake process by using a spark tracing and particle tracing techniques, changing the position of spark electrode.
Consequently, several characteristics of air flow induced into cylfinder, such as the direction, induced angle and center of swirlingflow, are determined at every crank angle and several cross-sectionsof cylinder.

抄録全体を表示

This paper deals with the two-dimensional steady flow of various rectangular channels with different widths and lengths. The flow in channel was simulated by the numerical analysis and the flow visualization. To solve the numerical calculation, the Navier-Stokes eqation was calculated by a up-wind difference method, and the flow visualization was visualized by dye injection method. The numerical calculation was done for Reynolds numbers between 10 and 300, and the flow visualization was carried out for Reynolds numbers more wide ranging from 30 to 700. To verify the validity of the calculation results, the results obtained by numerical solution were compared with those of the flow visualization, and effects of the variations of the channel shape and of Reynolds number on the flow in channel were clarified.

抄録全体を表示

With the recent rapid development of super computers, we are now able to perform large-scale computation of fluid. But, as the results are of such a large scale, techniques for visualization of the results of fluid simulation have become one of the most important problems for the researcher and engineer.
In this film, we tried some experiences on the visualization. The main objects of this film are (1) investigation of visualization techniques, (2) particularly, evaluation of different expressions of fluid or flow images, (3) estimation and prediction of application fields including not only tools for analyzing fluid simulation but also design, advertisement and education.
To accomplish these objects, we selected 3D horizontal buoyant jet, performed its numerical simulation, then prepared the five-minute film " Flow Fantasia'85 " by using computer graphic techniques.

抄録全体を表示

A newly developed algorithm, GSMAC, remove the main problems for analyzing unsteady flow fields by finite element method, CPU time consumption and maximum storage limitation. This algorithm uses the concept of orthogonal decomposition and cycle-to cycle self-adjustment method. Unsteady viscous flow fields around a circular cylinder are considered to prove the effectiveness. The solution obtained by GSMAC agrees very well with the experimental results by Perry et al., especially for Karman vortex shedding process. Shapes, length and other properties of a pair-vortex behind a cylinder are also compared and in good agreement with the experimental results by Bouard & Coutanceau.

抄録全体を表示

The recent great data processing speeds and memory capacity of computers have rendered possible numerical simulation of complicated turbulent flows. A numerical calculation system based on large eddy simulation is applied for the fully developed channel flow with turbulence promoters. Computational results are displayed using a microcomputer system supported by HITAC M280H system computer of University of Tokyo and animation of the flow is generated on a 16 mm film.

抄録全体を表示

Recently, turbulent models using reasonable assumption and approximation, such as two-equation model, Reynolds stress model, large eddy simulation model, are animatedly studied along with the development of the computer technology. In this study, the K-ε turbulent model, which is one of the representative two-equation turbulent models, is applied to an analysis of two-dimensional case of slot jet which is fitted out at the bottome of flume in the vertical direction, and the appropriateness of the flow profile obtained by the K-ε model is examined in comparison with the results of visualization experiment of production process of turbulent quantities.

抄録全体を表示

The requirement to visualize computer simulation results has been rising up recently. Computer graphics technique is the new method that can give an answer of that requirement. Following two systems are to visualize thermal-hydraulic analyses by computer graphic animation. The NPVS (Nuclear Plant Visual Simulation system) is for the single-dimentional thermal-hydraulic analyses, and the VISTA (Visualization System for Thermal-hydraulic Analysis) is for two-dimentional ones. These express heat-transfer phenomena by changing pseud-color of time-dependent temperature at everywhere on the analysis model.

抄録全体を表示

Recent developments in performance of personal computers have been making enable us to use them as terminals of color graphic systems. High resolutional color graphics and standerd installations of RS232C communication interfaces have been realizing in some personal computers.
There are increasing demand for color display of detailed measurement data such as in flow fields and temperature fields, and of results of numerical calculations for better understanding the phenomena of concerns.
This paper discribes a data visualization system developed under these circumstances using a personal computer for a color graphic terminal. Some examples of display by the system are also shown.

抄録全体を表示

It is known that the asymmetric unstable rotating flow exists in the fluid between two parallel rotating disks. This phenomenon which occurs in the magnetic disk memories induces the disk flutter.
The flow between two rotating disks has been visualized with alminium flakes, by means of smoke wire method and hydrogen bubble method. And as a result, it is proved that the hydrogen bubble method is effective to the quantitative identification of this flow.
In this paper, we succeeded in identifying this flow quantitatively and separating the steady flow and fluctuating flow from the asymmetric unstable rotating flow.

抄録全体を表示

Laser interferometry using Wollaston prisms was applied to density measurements in freely expanding flows issuing from a circular sonic orifice. The radially resolved densities were determined by means of the Abel inversion. The measurements were made at 20 axial stations. At each station, 1024 radial data were obtained, and from 1024×20 data of density, the density contours were drawn. The experiments were carried out for two different gases, argon and nitrogen. For comparison with experiments, the axisymmetric flow equations were numerically solved based on the operator splitting method for two-dimensional numerical calculations. Except for the flow region near the orifice, the comparison shows good agreement.

抄録全体を表示

This paper is concerned with the frequency of vortex shedding from a rectangular cylinder and flow pattern around it in a uniform shear flow. The experiment is carried out in a water channel by visualization used tracer technique and by L.D.V. measurements of velocity fluctuation near 10³ of Reynolds number. It is found that the critical shapes of rectangular cylinder between perfectly separated pattern and reattached one appear wider range of width-to-height ratio as larger shear rate of the incident flow.

抄録全体を表示

Turbulent diffusion plays a pricipal role in the mixing process of heated water discharged horizontally at the water surface. Experiments of visualization on the spread of heated water discharged at the water surface were conducted at the laboratory. It is observed that turbulent plumes have a sharp boundary separating nearly uniform turbulent buoyant fluid from the surroundings. This boundary is indented by large eddies and the mixing process takes place in two stages, the engulfing of external fluid by the large eddies, followed by rapid smaller scale mixing across the center core.

抄録全体を表示