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Tsuneyo Ando
1991 Volume 11 Issue Supplement2 Pages
1
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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Koji IZUMI, Teruyuki NAKAJIMA, Shigeru ASO, Michio NISHIDA
1991 Volume 11 Issue Supplement2 Pages
3-6
Published: October 01, 1991
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This paper describes computational and experimental studies of the focusing of weak shock waves reflected from paraboric and circular reflectors. The numerical calculation was carried out appling Piecewise-Liniear-Method to the two-dimensional Euler equations. The experiment was performed using a shock tube with air as driver and driven gases and the shock focusing flow field was visualized by a conventional Schlieren technique. These studies were conducted for five different shapes of reflector for an initial shock Mach number of 1.1.
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Haruaki KISHIGE, Koji TESHIMA, Michio NISHIDA
1991 Volume 11 Issue Supplement2 Pages
7-10
Published: October 01, 1991
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Computational and experimental studies of shock wave reflection from an ax-isymmetrical parabolic wall were conducted. From the results of the numerical calculations, the effects of incident shock strength upon the reflection process were discussed. The reflected shock waves were visualized by optical shadowgraph tech-nique using a conventional shock tube with air as driver and argon as driven gases and measured shock Mach number was 1.5. 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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Kiyoshi YAMADA, Tetsuro OBARA, Kazuyoshi TAKAYAMA
1991 Volume 11 Issue Supplement2 Pages
11-14
Published: October 01, 1991
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Shock propagation in a stratified liquid layer was investigated experimentally and numerically. A silicone-oil/water combination was investigated. In experiment a spherical shock wave was generated by exploding a 10 mg silverazide micropellet in silicone-oil. Propagation, reflection and refraction of the spherical shock wave over the silicone-oil/water interface was observed by double exposure holographic interferometry. TVD finite difference numerical simulation was also carried out to interpret complicated shock refraction over the two liquid interface. By comparison between the experiment and numerical solution, discussion was made in some detail.
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Hiroyuki HIRAHARA, Masaaki KAWAHASHI
1991 Volume 11 Issue Supplement2 Pages
15-18
Published: October 01, 1991
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Mach reflection of shock waves propagating through a fog was investigated experimentally with a shock tube. A fog was generated by the adiabatic expansion of the water vapor and air mixture by using a double diaphragm type shock tube. Mach reflection from an inclined flat surface was observed by means of shadowgraph method. As a light source, a nano pulse light was used. Shadowgraphs of Mach reflection have been obtained when an inclination angle of the flat surface was 20 degrees and the initial relative humidity of a mixture was changed from 50% to 90%. Experimental results shows that the incident shock wave was dispersed by the mist and the relaxation region was formed behind the shock front.
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Kazuyuki KAGE, Kiyoshi SHIGEMATSU
1991 Volume 11 Issue Supplement2 Pages
19-22
Published: October 01, 1991
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In this paper, the interaction phenomena of the reflected shock wave with the contact surface in a shock tube were investigated by numerical simulation in order to clarify the formation mechanism of the pseudo-shock wave. The computations were carried out by solving the two-dimensional, time-dependent and compressible Navier-Stokes equations by means of TVD method. The formation process of the pseudo-shock was visualized by the plots of the contour lines of the pressure andthe density, the velocity vectors, and the stream lines in the flow field, and the pressure distribution on the wall.
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Koji OKAMOTO, Motoo FUMUZAWA
1991 Volume 11 Issue Supplement2 Pages
23-26
Published: October 01, 1991
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In order to measure the transient density distribution of gas jet flow, automatic and high reliability system has been developed. The VTR images of Mach-Zehnder interferogram are automatically analyzed by the Engineering Work Station, resulting in the two-dimensional transient density distribution to be obtained. The calculated density distributions were compared with the data obtained by the probe type density meter, showing high accuracy.
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Tadatomo KOJIMA, Yoshihiro MATSUOKA
1991 Volume 11 Issue Supplement2 Pages
27-30
Published: October 01, 1991
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In this paper, the interaction characteristics of two parallel underexpanded jets for various intervals between two pipe axes were studied. In particular, the flow visualizations of instantaneous flows with time, the cell length, the length of pseudo-shock waves, and the characteristics of decrease in the center-line velocity were investigated.
As a results, it was found that the flows of two parallel underexpanded jets could be classified into 3 pattern, and the structures of pseudoschock wave within interacting flow were clarified.
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Hideo KASHIMURA, Tsuyoshi YASUNOBU
1991 Volume 11 Issue Supplement2 Pages
31-34
Published: October 01, 1991
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Self induced flow oscillation occurs when an underexpanded sonic or supersonic jet impinges on an obstacle. This oscillatory flow involves the movements of the Mach disk and pressure oscillation on the obstacle. In the present paper, a numerical simulation is carried out on a sonic jet impinging on a cylindrical body with the same diameter as the exit diameter of a nozzle. The flow field with the oscillation is visualized using computer color graphics and refer to a locus of the Mach disk and pressure disturbances of the wall surface on a cylindrical body.
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Hiroaki MOCHIZUKI, Yoshiaki MIYAZATO, Yoshitomo SATO, Hirohumi YAMAGUC ...
1991 Volume 11 Issue Supplement2 Pages
35-38
Published: October 01, 1991
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Supersonic axisymmetric jets from various kinds of small nozzles with a throat diameter of a few millimeters and an exit Mach number of 1.0-5.9 are optically observed. The jet from a tapered divergent nozzle has a cell structure even in a correct-expanded case. The over all pressure ratio for a correctexpanded jet and the cell structures of jets are discussed in detail.
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Masahiro INOUE, Mitsuharu MASUDA, Takashi MURAISHI
1991 Volume 11 Issue Supplement2 Pages
39-42
Published: October 01, 1991
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In the large-scale gas or stream turbine, the flow around the blade tip becomes transonic, and the shock waves are generated in the blade passage. These shock waves induce the boundary layer separation and the vibrations of blades, which degrade the efficiency. This unstable flow phenomenon is closely related to the secondary flow associated with the large change in flow direction in the blade passage. To measure the secondary flow, the nonintrusive diagnostic technique is desirable, and the laser-induced fluorescence (LIF) method offers one of the best tools for this purpose. To prove the validity of LIF method in determining the temperature of the transonic flow field, the transonic nozzle with rectangular cross-section was made. The temperature calculated from the measured LIF intensity in the nozzle was shown to agree very well with that obtained from the static pressure measurement.
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Tomohide NI-IMI, Tetsuo FUJIMOTO, Kenichi IJIMA, Nobumasa TAOI, Nobuyu ...
1991 Volume 11 Issue Supplement2 Pages
43-48
Published: October 01, 1991
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The structures of two opposed supersonic argon free jets with different source pressure are studied by flow visualization using laser-induced fluorescence of iodine molecules seeded in argon. A ratio between source pressures is ranged between 3.0 and 5.0. Experi-ments are carried out for various source pressures and various ratios of the source pressure to the pressure of the expansion chamber. Characteristic structures of the flow field are classified roughly into four types depending on the condition of the source pressures and the pressure of the expansion chamber. Specifically, an unstable flow in the interacting region are found. The condition of pressures is examined for each type of the flow field.
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Hiromasa KAWAI, Hiroaki MIHARA
1991 Volume 11 Issue Supplement2 Pages
49-52
Published: October 01, 1991
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Mechanism of flow induced vibration of a circular cylinder with a splitter plate was investigated by flow visualization techenique using the smoke wire method. When the distance between the cylinder and the splitter plate is within some 2.5 diameter of the cylinder, the shear layer of the stationary cylinder reattachs on the plate not to form the reqular vortex. On the other hand, the shear layer of the vibration cylinder is always rolled up reqularly synchrounously with the vibration even when it reattachs on the plate. When the distance is 1.5 diameter, the strong vortex sheds into the wake by the interaction of the rolling up of the shear layer and the edge of the plate, then the strong flow induced vibration is induced.
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Kesayoshi HADANO, Takashi SAITOU, Meiko ENDOU, Noriyoshi NAKAMURA, Yas ...
1991 Volume 11 Issue Supplement2 Pages
53-58
Published: October 01, 1991
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Flow pattern around a circular cylinder located in a harmonically oscillatory flow is visualized using the tracer particle method. The technique which enables to distinguish the directions of movements of the individual particles on a photo-print was employed. Both descrip-tions of the flow fields using the contour lines of vorticity and equivalent vortex strength, which are based on the resultant data of the velocity vector distributions, are presented.
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Effect of Passive Boundary-Layer Control
Toshiaki SETOGUCHI, Toshihiro NAKANO, Takashi TOMINAGA, Kenji KANEKO
1991 Volume 11 Issue Supplement2 Pages
59-62
Published: October 01, 1991
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A passive boundary-layer control, which consists of porous wall with cavity, may be the useful technique for alleviation of shock oscillations. In order to clarify the effect of the control on flow patterns around a cylindrical protuberance in the supersonic flow, flow visualizations have been carried out using the vapor-screen method.The flow patterns have been shown especially for the three-dimensional shock configurations, and compared with those for solid wall. Results indicate that there appears the distinct difference in shock structures.
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Kazuo OHMI, Kensaku IMAICHI, Ei-ichi TADA
1991 Volume 11 Issue Supplement2 Pages
63-68
Published: October 01, 1991
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The interacting vortex wakes of two circular cylinders in staggered arrangement are examined by visualization experiments using a towing water tank. The cylinder spacing parameters are expressed in terms of the stream-wise spacing ratio L/d (0 to 10.0) and the transverse spacing ratio T/d (0 to 4.0) for a fixed Reynolds number of 80. The point of the present study is the flow pattern analysis in various geometric arrangement of the two cylinders, covering a wide range of spacing para-meters, inclusive of the so-called bistable regime of vortex shedding, and the simultaneous measurement of Strouhal numbers corresponding to the wake frequency detected outside the near-wake region. Another point of the paper is the complicated vortex wake interaction and the subsequent wake evolution observed downstream of the leeward cylinder.
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TAKASHI SAITOU
1991 Volume 11 Issue Supplement2 Pages
69-72
Published: October 01, 1991
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The flows and the process of the formation ans the shedding of the vortex-ring behind aimpulsively started spheres at aconstant speed in still water were photo-graphycally observed by the means of the electrolyses method. The permanent vortex-ring was confirmed at the Reynoulds number is higher than 24 by means of alminium dust method, however, as the results of this experiment, the flows behind a sphere was found to be perfectory laminer and no vortex-ring until Reynoulds number of 80 is reached. The formation of the vortex-ring and the hair-pin vortex-loop after partialy detachement of the vortex-ring was observed at Reynoulds number is about 600.
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Ryozo ISHIWATA, Takashi KAWAGUCHI
1991 Volume 11 Issue Supplement2 Pages
73-76
Published: October 01, 1991
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Fluid force and Karman-vortex induced by manipulators of marine robots tend to make control of the robots difficult. We regarded a cyl-inder as a manipulator of robot and observed flow past the cylinder ro-tated horizontally around a vertical axis through one side of it in order to show the behaviour of Karman-vortex shedding from it. We used hydrogen-bubble method and recorded the flow on videotape by a camera moving with the cylinder.
Strouhal number St based on peripheral velocity at outer end was obtained under some range of Reynolds number Re. that is. St= {-.7em}\
aisebox{1.1ex}{.} {.1em}\
aisebox{-0.2ex}{.}0.12 for 1.16×10
3≤ Re≤ 4.13≤ 10
3 and
l/d=10. St= {-.7em}\
aisebox{1.1ex}{.} {.1em}\
aisebox{-0.2ex}{.}0.06 for 1.72×10
3≤ Re≤ 4.76×103 and
l/d=6.53. where
l and d are length and diameter of the cylinder.
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Kouju SHIOZAKI, Haomin LI, Hiroyuki HIRAHARA, Masaaki KAWAHASHI
1991 Volume 11 Issue Supplement2 Pages
77-80
Published: October 01, 1991
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Density fluctuation caused by velocity fluctuation around a plane mirror scanner is one of the most important factors to determine the accuracy of laser pointing system.
Flow field produced by a rotating plane mirror is very complicated and three dimensional, and the maximum amplitude of density fluctuation in the flow field caused by velocity fluctuation cannot be disregarded to consider laser beam deflection.
In this report, to known fundamental flow field around the plane mirror scanner, visualization and velocity measurements of flow produced by a rotating plate are performed by means of laser-light-sheet method and a hot-wire anemometry.
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Comparison with Circular Cylinder without Grooves
Makoto OKI, Masumitsu SUEHIRO, Hiroo OKANAGA, Katsumi AOKI, Yasuki NAK ...
1991 Volume 11 Issue Supplement2 Pages
81-84
Published: October 01, 1991
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It is well-known the dimples on the surface of golf ball increase its flying distance. But the detailed mechanism of flow by dimples has not been made clear. This paper deals with the effect of the grooves as modeled dimples that were put on the surface of a circular cylinder. The computation was performed by solving the Navier-Stokes equation using the QUICK method. The grooves were formed in the same shape as a golf ball and the number of dimples is 32. The experiment was performed flow visualization using spark tracing method. These results of the flow pattern around the circular cylinder showed good agreement.
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Masaaki Ohba
1991 Volume 11 Issue Supplement2 Pages
85-88
Published: October 01, 1991
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The ventilation characteristics in large half-enclosed building spaces were investigated for spherical dome models, a cylindrical building model and a rectangular one using video digital image processing techniques. In the case of the spherical dome models, mean video image signal values in the domes were inversely proportional to the opening ratios of the movable roof. The height of separated flows above the movable roofs was found to be the largest in the case of the rectangular building model. The average time of video image signals showed that 25 seconds was seen to be long enough for the running average to stabilize.
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Osamu ISHIHARA, Ikuo SAITO, Takashi YOSHIDA
1991 Volume 11 Issue Supplement2 Pages
89-92
Published: October 01, 1991
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We constructed a region environment information database using remote sensing data, digital national land information and so on. The object areas are Kumamoto City, Yatsushiro City and Kumamoto Prefecture.
From remote sensing data corrected for geometrical distortion, the land cover classification map and ground surface temperature map were extracted as the image information. The administration data and digital national land information were translated into image information that is the same format as the remote sensing image. The map coordinates of administrative boundary line and so on were incorporated into database as the line or point information.
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Yukio URUSHIDO, Shigenori WATAYA
1991 Volume 11 Issue Supplement2 Pages
93-96
Published: October 01, 1991
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We have developed a personal computer simulasion system for the acoustic design. In this system, internal sound field is simulated by sound ray tracing method and image method based on geometrical acoustic theory, and visualized with computer graphics. To visualize internal sound field obtained by simulation is very useful way to exactly grasp characteristics of internal sound field and to easily reflect the simulated results to the acoustic design.
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Hiroshi HOMMA, Chulgoo LEE, Ingoo KIM
1991 Volume 11 Issue Supplement2 Pages
97-100
Published: October 01, 1991
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A human body transfers about 35 percent of its metabolic heat to the ambient air by convection. This heat causes upward natural convection around the body. The characters of the convection were observed by infrared photography and smoke wire photography technics. Its velocity reached to about 0.25 m/s at 0.3 m above the head, and its flow rate was about 40 1/s. As the results of it, the convection heat transfer coefficient at the lower leg was about two times of it at the torso. The concentration of occupant produce carbon dioxide was higher in the overhead region than in the lower region of.a room. It is important to consider the influecne of the natural convection in thermal comfort and ventilation design.
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Takahiro ISHII, Junta DOI
1991 Volume 11 Issue Supplement2 Pages
101-104
Published: October 01, 1991
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The tube representation of three dimensional trajectories using 4th order B-splines and quintic splines is presented. Lines or curves have been used to display trajectories such as streamline, electric force line, and various trajectories of moving objects. A still picture, depicted by using this tube models, is able to express a shape of the trajectory, velocity, acceleration, and various attributes in a three dimensional manner, because a tube has a finite volume and it can assign local variables such as size, tortuosity, color, and texture. This representation is useful to analyze various object motions comprehensively.
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Mitsunori Ikeguchi, Junta Doi
1991 Volume 11 Issue Supplement2 Pages
105-108
Published: October 01, 1991
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A method to visualize iso-value surfaces of bio-molecular properties using 3-D solid models is proposed. The marching cube algorithm is improved to construct a 3-D solid model for this purpose. A program that generates iso-value surfaces of molecular properties such as non-bond interaction energy is developed. Boolean operation on solid models is efficient to analyze shapes of active sites of bio-molecules. For example a fundamental study of molecular design for Trypsin - Trypsin inhibitor complex is demonstrated. This method allows more comprehensive analysis of bio-molecular structure.
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Kazuhide DAN, Motoaki YANO
1991 Volume 11 Issue Supplement2 Pages
109-114
Published: October 01, 1991
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The application of the holography theory to the design of the structures for breaking water wave in the desired sea shore region is shown in this paper. The structures for breaking water wave consist of many vertical piles of cylinders. Using Holography theory we determined the arrangement of cylinders.
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(1st Report Tracer Method by Changing Color Codes for Palettes)
Ryozo ISHIWATA, Takashi KAWAGUCHI
1991 Volume 11 Issue Supplement2 Pages
115-118
Published: October 01, 1991
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It is useful in education on fluid dynamics to show animated computer graphics expressed some kinds of flows, since they are dynamic phenomena. Therefore some animation programs by means of tracer method in which tracer points along streamline were successively illuminated by changing color codes for palettes were developed in this report. They were applied to potential flow around a rotating cylinder and around a joukowski aerofoil, Pitot tube in a flow, flow in an inlet section of a pipe, vortex flow, laminar and turbulent flow in a pipe.
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(2nd Report Animation by Changing Screens and Others)
Ryozo ISHIWATA, Takashi KAWAGUCHI
1991 Volume 11 Issue Supplement2 Pages
119-122
Published: October 01, 1991
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Some animation programs have been developed for computer aided education on fluid dynamics. In the first report tracer method was applied to them. The programs in the present report were used methods in which screens were successively exchanged to animate, in which parts of screen were moved by "GET" and "PUT" commands or in which pictures were drafted in disappeared screen every moment. They were applied to sloshing in a square tank, secondary flows in a bent pipe and a square pipe, a convergent flow, Couette flow and a forced vortex.
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Eiji MUKAI, Hirotsugu OHSHIMA, Ryu-ichiro OHYAMA, Kiyoji KANEKO
1991 Volume 11 Issue Supplement2 Pages
123-126
Published: October 01, 1991
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In this paper, we present the visualization system of electric field distribution and tolerance for insulation strength by means of personal computer-aided engineering (PCAE) system. The PCAE system is a combination of computer-aided design (CAD) and electric field analysis with finite element method (FEM). The CAD system contains a fully automatic meshing procedure for adapting the FEM. Our system is applied to evaluation or computation of electric fields such as a 275kV XLPE cable. The visualization of tolerance for insulation strength is very useful as an aid in designing insulators.
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Shinsuke ONO, Eiichi MURASE, Hideaki KAWANO, Mitsuo NAKAYA, Guen Sun L ...
1991 Volume 11 Issue Supplement2 Pages
127-130
Published: October 01, 1991
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By making use of the rotary cylinder combustion device which rotates with the combustible mixture in it, the real effects of the centrifugal force environment in the solid vortex on the flame behaviors are examined. The observed results show the enhanc-ed combustion by the swirl is not always expected, because of the rapid motion of a flame kernel to the swirl center, and the laminarization of turbulent flame. The propaga-tion speed of the flame initiated near the swirl center is considerably reduced, and in some cases, depending on the flame structure, vanishes to extinguish the flame.
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Shinji KOBAYASHI, Shigeru SHUNDOH, Toshio NAKAHIRA, Masanori KOMORI, K ...
1991 Volume 11 Issue Supplement2 Pages
131-134
Published: October 01, 1991
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The high pressure fuel injection is very effective for improving NOx and particulate emission from diesel engine. To understand the mechanism of combustion improvement, the observation of combustion phenomena was performed using high speed laser shadowgraph technique. The results indicate that ignition and flame development process is different from base engine in the case of high pressure fuel injection. It becomes clear that combustion is improved by increasing entrained air into spray, rapid mixing between fuel and air.
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Kenji ONO, Ryutaro HIMENO, Katsuro FUJITANI, Sanae SATO
1991 Volume 11 Issue Supplement2 Pages
135-138
Published: October 01, 1991
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Computational analysis was performed for the external flow around an automobile and the internal flow in the engine compartment using a multi-block grid system and a finite-difference method. Cooling performance of the radiator is evaluated by the flow quantity passing through the radiator. Computational results show quite good agreement with experimental data. Present method is applied to the design of an the inter-cooler, it shows that the cooling performance of the inter-cooler could be improve by changing the duct configuration.
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Tateyuki SUZUKI, Takashi ADACHI, Susumu KOBAYASHI, Kazuyoshi UCHIDA
1991 Volume 11 Issue Supplement2 Pages
139-142
Published: October 01, 1991
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To find the mechanism for cooling hot semi-conductors in an alternator mounted on an automobile is important to improve performance of an automobile. The cooling fan on the front end of the alter-nator is installed to suck an air through inlets of the rear cover in order to cool down the hot semi-conductors just inside the rear cover. Thus the cooling air flow is opposite in direction to the movement of an automobile. The flow speed is about I m/s around the alternator. To visualize such a slow air flow the smoke is used, which is produced by burning joss sticks in a specially designed generator. Visualized smoke streaks are analyzed by dig-ital image processing. The obtained streaks show that the flow rate through rear inlets is much smaller than that through the holes on the side wall of the alternator used in our study.
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Masahiro SHOJI, Masahiro YOSHIWARA
1991 Volume 11 Issue Supplement2 Pages
143-148
Published: October 01, 1991
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Pool boiling heat transfer from a thin wire of which diameter is 0.2 mm to distilled water is experimentally studied under atomos-pheric pressure. Observation of boiling is made under the following two conditions; one is saturated boiling, and the other is subcooled boiling of which subcooling is 59.4 K. In case of subcooled boiling, microbubble emission is observed from a beginning of nucleate boiling regime to burnout point in the whole length of a thin wire.
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K. NOTO, K. MATSUZAKI, H. NAKANISHI, T. NAKAJIMA
1991 Volume 11 Issue Supplement2 Pages
149-152
Published: October 01, 1991
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The present numerical computations and flow visualizations showed the generation of the Karman vortex street and the change of its vortex shedding upon cooling a circular cylinder submerged in an upward free-stream of air at the low Reynolds number. The dominant causes of the generation of the vortex and the decrease of the Strouhal number in the opposing flow were made clear from points of view of changes of the kinematic viscosity, separation points, wake velocity, and vorticity upon cooling the cylinder.
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Masakazu TATSUNO, Takasi KARASUDANI, Hajime AMAMOTO, Koji ISHI-I
1991 Volume 11 Issue Supplement2 Pages
153-156
Published: October 01, 1991
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The developing process of the boundary layer flows from laminar to turbulent is observed when a laminar boundary layer flows on a horizontal flat plate is heated locally from below.
The thermal instability occurs in the boundary layer flow over the heated section and the longitudinal vortices appear in the spanwise direction. As the longitudinal vortices move in the downstream direction, they become unstable and merge into large scale vortices. Simultaneously, a streamwise periodic structure also appears in the flow.
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Satoru GIMA, Xing ZHANG, Toshio TOMIMURA, Motoo FUJII
1991 Volume 11 Issue Supplement2 Pages
157-160
Published: October 01, 1991
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An experimental investigation is made on natural air cooling of five vertical parallel IC boards with equal interval and the same sizes (285
hx237
w mm
2) of each board, where gap between the boards ranges 9.8 to 34.8mm and heat generated per each board from 3.5 to 16.0W. The temperature fields among boards are visualized be Mach-Zehnder Interferometer in the three different regions to show the effects of packages, gaps and heat fluxes. The surface temperatures of packages and boards are also measured by copper-constantan thermocouples. Discussions are made by comparing the local Nusselt numbers obtained with the previous correlation.
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Hidemi YAMADA, Hideo OSAKA
1991 Volume 11 Issue Supplement2 Pages
161-164
Published: October 01, 1991
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The vortex structure around a rectangular plate standing vertically on the flat wall where the laminar boundary layer was developing was examined by visualization technique. The structure of the vortices shed from the rectangular plates of w/h=0.5, 1 and 3 can be classified into four patterns A-D in terms of both the Reynolds number Rew and the ratio of plate height to boundary layer thickness h/δ. The pattern A shows the horseshoe trailing vortex, the pattern B shows a pair of trailing vortices, the pattern C shows the symmetrical hairpin vortices, and the pattern D shows the irregular hairpin vortices. It seems that the mean flow patterns on the grand wall behind the rectangular plates are closely related with four types of the vortex structure shed from those plates.
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Nobuyuki FUJISAWA
1991 Volume 11 Issue Supplement2 Pages
165-168
Published: October 01, 1991
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Developing processes of longitudinal vortices produced in turbulent wall jets along a concave surface are studied by flow visualization with smoke-wire method and moving laser-sheet technique. It is found that the formation of the vortices is mainly due to the spanwise secondary-flow-motion in the wall region, while they grow normal to the surface in the downstream reaching to the middle of the jet region. The vortices in the downstream are strongly affected by the intermittent turbulent-structure in the jet region so that they behave unsteadily in space and time .
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Toru KOSO, Akihiko UCHINO, Sei NAGASAWA, Hiroshi HAYAMI
1991 Volume 11 Issue Supplement2 Pages
169-174
Published: October 01, 1991
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Perspective view of vortex structure in a fully developed region of a three-dimensional wall jet is reconstructed by applying digital image processing to motion pictures visualized using laser-induced fluorescence. The fluorescence dye was premixed to jet fluid, and a cross section normal to jet axis was illuminated by a thin laser sheet. The time of motion pictures is converted to longitudinal position by Galilean transformation of which constant is a convective velocity of the structure. A fast and memory saving computer program for image stacking is developed to process the pictures by using a personal compuer with a video image memory board. Three-dimensional pictures of vortices indicate that the jet flow is filled with numerous streamwise vortices and that some of them form U-shape bend vortices of which top is inclined to backward and outward. Furthermore, temporal variation of this structure is examined to confirm the applicability of the Galilean transformation.
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Masahiko SOSHINO, Tetsuhiro TSUKIJI
1991 Volume 11 Issue Supplement2 Pages
175-178
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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The jet flow, when the valves are immediately opened, issuing from the metering orifice of the spool valves commonly used for hydraulic power applications is investigated by flow visualization test. A two-dimensional model of the spool valve is designed to visualize the jet flow by a hydrogen-bubble method. The images of flow fields taken by a CCD monochrome camera are fed into a microcomputer, and a digital image processing technique is employed to investigate the process of reattaching jet formation. The influence of the Reynolds number and the spool speed on the time required of the jet from the orifice to the wall is described.
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Masahiro Ikegawa, Yoshimitsu Hiro, Masayuki Kaiho
1991 Volume 11 Issue Supplement2 Pages
179-182
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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A new FEM/FDM composite scheme for two-dimensional incompressible flow problems combining the finite element method which is best suited to analyse flow in any arbitrarily shaped flow geometry and the finite difference method which is advantageous in both computing time and computer storage is presented. The combination of both methods enables large-scale viscous flows to be analysed and it is crucial for both the detailed analysis of three-dimensional flows and the solving of flow problems around moving bodies. Numerical results for cars of a railroad car entering a tunnel and cars passing each other correlate well with results obtained by measurements on actual cars and model analysis.
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Susumu NAKANO, Kuniyoshi TSUBOUCHI, Hiroshi HIGAKI
1991 Volume 11 Issue Supplement2 Pages
183-186
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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When a high speed train, such as bullet train, passes through a tunnel, pressure fluctuations act on the body because of the propagation of pressure waves generated by the train entering a tunnel. In this report, a numerical analysis method for unsteady one-dimensional compressible flow, in which the method of characteristics is employed, is presented. A computer program using this method was used to investigate the propagation of pressure waves and pressure fluctuations. Calculations are performed with a train velocity of 300km/h. Results of pressure profiles in a tunnel, profiles of the rate of change of pressure, and pressure histories at front and rear sections of the train are presented.
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Sutham Teerawatanachai, Kin-ichi Komiya, Hiromichi Sasamoto, Nariaki O ...
1991 Volume 11 Issue Supplement2 Pages
187-190
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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The technique of computed tomography (CT) was used to estimate the velocity profile of axisymmetric flow of air from the average velocity, obtained from ultrasonic (US) flowmeter, over 4 different paths of propagation of ultrasonic wave. 2 experiments, where motor fan and air compressor were used as the air source, were performed and the results are repoered.
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Shiro SUGIYAMA, Masaaki YAMAMOTO, Youiti ODA, Michiyoshi KUSAKA, Soich ...
1991 Volume 11 Issue Supplement2 Pages
191-196
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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Flow visualization and LDV measurement were carried out to investigate the secondary flows occurring in an azimuth 180°curved duct and in its attached outlet duct. The Dean number was 220. The flow pattern obtained by the visualization method corresponded to the result conjectured by the LDV measurement at the 180°cross-section, and did not in the outlet duct. The vortex flow pattern observed at the 180°cross-section flows in the downstream as diffusing gradually. The pattern was appeared even at Z0=9Dh. However, the secondary flow was not detected there by the LDV measurement, because the upstream conditions are still preserved in the downstream.
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A Case of Higher Pressure Recovery
Takamitsu Ohshima
1991 Volume 11 Issue Supplement2 Pages
197-200
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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The inner flow situated just behind the regular pyramidal diffuser inlet is a complicated turbulence with a shear voltex produced by separated flow at the diffuser inlet wall and voltex produced by secondary flow at the four corners of the diffuser.
This turbulent flow could be visualized by the tuft method. Photographs and continuous images of it were taken by a telephotographic camera and video tape recorder placed on the diffuser axis downstream from the diffuser outlet.
The power spectrum of static pressure fluctuation was measured at a point on the wall downstream L/W=0.5 from the diffuser inlet.
From the above, it follows that there is a unique flow pattern determind by the diffuser divergence angle and throat Reynolds number.
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Masayasu NOMA, Atsunobu MORI
1991 Volume 11 Issue Supplement2 Pages
201-204
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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Fluid flow in clearance of pivoted-pad journal bearing was visualized. Flow visualization was performed by means of hydrogen bubble method.
The experiments were carried out for parallel and wedge film. In the case of wedge film type, it was observed that Taylor vortices occur from behavior of streak line. Furthermore it was observed that the difference between one pad type and four pads type exists.
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Tatsuya HASEGAWA, Hironaga GOTOH, Shigeki YAMAGUCHI
1991 Volume 11 Issue Supplement2 Pages
205-208
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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Vortical structure and mixing process of a confined plane mixing layer (u
2/u
1=0.67, angles of the confined walls = -4 - +6 degree) were visualized using a laser sheet and a high-speed imaging system at a rate of 333frames/s. The system detected an area of 40mm×50mm with a spatial resolution of 0.5mm. Images of water vaporconcentration in a high-speed side flow showed a two-dimensional coherent structure and its entrainment process. The visualized concentration images were analyzed to get average concentration, fluctuation intensity, and the spatial correlation. As the angles of the confined walls became larger, the mixing layer developed faster and the distance between the vortices decreased. Thefreq uency of the vortices was, however, 53Hz for all angles of walls.
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Takanori SAGA, Hirofumi OHNARI, Katsutoshi WATANABE, Takashi SAITOU
1991 Volume 11 Issue Supplement2 Pages
209-212
Published: October 01, 1991
Released on J-STAGE: July 31, 2009
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Large-scale coherent structure in an turbulent channel flow are visualized by three methods. One is plan view methods used of fluorescent dye tracer excited by ultraviolet lamps. And the others are plan and streamwise sectional view methods that utilize fluorescent dye excited by a sheet of laser light. By synthesizing each results of their visualization methods, a few features of large- scale coherent structure are cleared. Large-scale coherent structure are formed by concentrating of wall streamwise vortices. And large- scale coherent structure have branch vortical structures at both sides.
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