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Masaru USAMI
Article type: Article
Session ID: 2339
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The new intermolecular collision scheme is developed to obtain an excellent result even if cells are lengthened in the direct simulation Monte Carlo (DSMC) calculation. In the new scheme, the velocity of one molecule of a collision pair is modified before and after a conventional collision calculation, assuming that velocity distributions in all flow-field are in local equilibrium with some temperature and flow velocity. The DSMC method with the new collision scheme is applied to three-dimensional supersonic free jets and two-dimensional vortices shedding behind a flat plate or a circular cylinder. When considering easy decision of boundary conditions and no divergence of calculation in the DSMC method, it is worth recognizing anew the possibility of the method to compressible fluid.
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Yuji NISHIYAMA, Yong-Hun KWEON, Yoshiaki MIYAZATO, Toshiyuki AOKI
Article type: Article
Session ID: 2340
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes an experimental work to reduce supersonic jet noise using a mesh screen device that is placed at the nozzle exit plane. In order to perturb mainly the jet shear layer, the inner diameter size of a mesh screen device is changed. The effect of an inner diameter of a mesh screen device on the jet structure and sound generation is experimentally investigated. A high-quality Schlieren optical system is used to visualize the flow field of supersonic jet with and without the mesh screen. Acoustic measurement is performed to obtain the overall sound pressure level and noise spectra. Based upon the results obtained, the effectiveness of the mesh screen device for reducing supersonic jet noise is discussed in detail. Furthermore, the present results for the mesh screen are also compared with the cases of tabs and a wire device.
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Hiroyuki HIGA, Minoru YAGA, Yoshio KINJO, Shoichi MATSUDA, Kenyu OYAKA ...
Article type: Article
Session ID: 2341
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this paper, twin underexpanded impinging jets are experimentally studied. The experiments were performed by static pressure fluctuation measurements on the wall and by schlieren method. The main parameters for the twin jets are the nondimensional distance between the two nozzle centers H/D 2.0, the nozzle to plate separation L/D 2.0 and 3.0 and the pressure ratio defined by P_0/P_b 3.0〜4.0, where D is the diameter of each nozzle exit, P_0 the stagnation pressure and P_b the back pressure. In case of L/D 2.0 and P_0/P_b 3.75, a Mach disk repeats the formation and disappearance due to the unsteadiness of the so called Fountain flow affecting the both main jet boundaries. It is found that severe pressure fluctuations were observed under the above condition.
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Shuhei NAGATA, Seiji SHIOZAKI, Yukinori SAKIYAMA, Yoichiro MATSUMOTO
Article type: Article
Session ID: 2342
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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High energy molecular beam source in the range of 1 to 5 eV is one of the most important tools to explore gas-surface interaction involving chemical reaction. Although the seeded beam and the arc-heated beam have been employed for such purpose, they have the drawback of the low beam intensity and the generation of undesirable excited species. It is known that the shock heated molecular beam is capable of overcoming these problems. However, the quite low repetition rate less than 1Hz has made practical application difficult in molecular beam scattering experiment so far. In this study, we examine the capability of the small shock tube as a molecular beam source using a current-loop valve and modify it to improve the performance.
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Masaru Fujinami, Hiroyuki Hirahara, Masaaki Kawahashi
Article type: Article
Session ID: 2343
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We use the shock wave, which propagate to atmosphere, induced by LSP (Laser Shock Peening) as a fundamental study to control a micro flow. We used a shock wave to occur by collection of light, plasma with a laser in the atmosphere by former technique, but conventional technique can occur by a shock wave at competition, a much lower energy density by the technique used LSP. We investigated the shock wave Mach number for an incidence energy density as a fundamental study of micro flow control by LSP. In addition, we carried out a quantitative measurement of density gradient distributions by speckle graph technique. In comparison with former technique, that a shock wave occurred at a much lower energy density was confirmed.
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Shigeru MATSUO, Shinya NAKANO, Toshiaki SETOGUCHI
Article type: Article
Session ID: 2344
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The shock tube is a useful tool for simulating the various compressible flows. In the theory of ideal shock tube flow, it is customarily assumed that the unsteady expansion wave generated by diaphragm rupture is a perfectly centered plane wave. However, such wave is generally not centered. In some experimental applications, the question arises as to how to evaluate or characterize the non-centered waveform. In the present research, the numerical study was carried out in order to investigate the effect of the diaphragm rupture of the shock tube on the characteristics of expansion wave. As a result, the effect of diaphragm rupture process on the flow field in the range close to the diaphragm was clarified, and the results obtained from numerical simulations were compared with the experimental ones.
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Shigehisa OASA, Masaharu KAMEDA, Yutaka AMAO
Article type: Article
Session ID: 2345
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We succeed for making porous binder for pressure-sensitive paint (PSP) on stainless steel by sol-gel method. We used the Yoldas method to make aluminum hydroxide sols, which were synthesized from aluminum isopropoxide with nitric acid. Ethylene glycol polymer was added to make the porous structure. Thin alumina gel layer was formed on the stainless steel by dip coating technique. Finally, the layer was calcined in air with 500℃. The sols at 0.16-0.43 mols of acid per mol of alcoxide exhibit thixotropy, which is appropriate to be coated on hydrophobic stainless steel. Scanning electron microscope observation displays that a mezzo porous structure whose porous diameter is 10nm to 100nm was obtained with the aid of template polymers. The pressure sensitivity of the present sol-gel PSP is close to the anodized aluminum PSPs.
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Ryuta MOTONE, Kazuyuki KAGE, Katsuya Ishimatsu, Toyoyasu OKUBAYASHI, H ...
Article type: Article
Session ID: 2346
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this paper, the attenuations of weak shock waves propagating in the duct with the ditched wall were investigated numerically. The computations were carried out by solving the two dimensional compressible Navier-Stokes equations by using total diminishing variation (TVD) scheme. The effects of attenuation of the shocks by the ditched wall were clarified by various diagrams.
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Tsuyoshi Yasunobu, Hideo Kashimura, Toshiaki Setoguchi
Article type: Article
Session ID: 2347
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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When the pulsating pressure wave propagated in the tube reaches at open end of tube, the reflection and emission of pressure wave occur and the multiple impulsive waves are formed. This multiple impulsive waves cause the some noise problems as like exhaust tube of automobile. It seems that the characteristics of multiple impulsive waves and the formation mechanism of multiple impulsive waves have to be more cleared to control the noise problem. This paper aims to clear the characteristic of multiple impulsive waves, the relation between the pulsating pressure wave and multiple impulsive waves. The numerical and experimental investigations were carried out using the TVD method.
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Tomoya TATEDA, Yong-Hun KWEON, Yoshiaki MIYAZATO, Toshiyuki AOKI
Article type: Article
Session ID: 2348
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes computational work to understand the unsteady flow-fields formed by the shock wave impinging upon a plate plane. A flat plate is located normal to the axis of a duct. The distance between the exit of the duct and flat plate is changed. Two different duct geometries (i.e., square and cross) are simulated in the present computation. In computation, the TVD scheme is employed to solve three-dimensional, unsteady, compressible, Euler equations. Computational results can predict three-dimensional dynamic behavior of the shock wave impinging upon the plate plane. The results obtained show that for the duct with cross-type exit, the unsteady loads acting on the plate plane are less, compared with those for the square duct.
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Shigeru MATSUO, Kazuhiro UMEZAKI, Toshiaki SETOGUCHI
Article type: Article
Session ID: 2349
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The free jet impinging on a solid surface can be found in various engineering applications. These impinging jet flow fields are generally found to be extremely complex. The structure of impinging jet is dependent on the design Mach number, that is, nozzle geometry, nozzle pressure ratio, the distance between nozzle exit and flat plate, and so on. On the other hand, in the supersonic flow of an actual jet burner, a steam turbine cascade and various industrial jet technologies, condensable gas may be used as working gas. In these cases, the non-equilibrium condensation may occur at the region between the nozzle exit and an obstacle. The objective of this study is to clarify the effect of the non-equilibrium condensation of moist air on characteristics of the axisymmetric under-expanded air jet impinging on a vertical flat plate numerically.
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Yumiko OTOBE, Hideo KASHIMURA, Shigeru MATSUO, Toshiaki SETOGUCHI
Article type: Article
Session ID: 2350
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In the present study, a computational fluid dynamics method has been applied to investigate the effects of initial degree of supersaturation at reservoir condition on under-expanded sonic jet structures, such as Mach disk location and diameter, barrel shock wave and jet boundary. The axisymmetric nozzle geometry investigated was a contoured converging nozzle with straight part. As a result, it was found that the characteristics of flow with occurrence of non-equilibrium condensation in the jet were different from those without condensation.
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Shigeru MATSUO, Yuki OGATA, Toshiaki SETOGUCHI
Article type: Article
Session ID: 2351
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The unsteady phenomenon in the transonic flow around airfoils is observed in the flow fields of fan, compressor blades and butterfly valves, and this causes often serious such problems as the aeroacoustic noise and the vibration. In the transonic or supersonic flow where vapour is contained in the main flow, the rapid expansion of the flow may induce a non-equilibrium condensation. However, the effect of non-equilibrium condensation on the transonic internal flows around the airfoil has not yet been clarified satisfactorily. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation on a circular arc blade was investigated numerically. The results showed that in the case with non-equilibrium condensation, the frequency of the flow oscillation became smaller than that without the non-equilibrium condensation.
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Hiroshi KATANODA, Minoru FUKUHARA, Naoko IINO, Seiji KURODA, Jin KAWAK ...
Article type: Article
Session ID: 2352
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The two-stage High Velocity Oxy-Fuel (HVOF) thermal spray gun developed by the authors has a mixing chamber between a combustion chamber and a supersonic nozzle followed by a straight barrel. The combustion gas is discharged into the mixing chamber, then the gas temperature is lowered in the chamber by injecting nitrogen gas at room temperature. The lowered gas temperature is beneficial from the view point of less oxidation of the spray particle. In this paper, the gas properties in the mixing chamber are calculated for a wide range of mass flow rates of nitrogen gas.
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Souichi YAMAO, Hiroshi KATANODA, Minoru FUKUHARA, Naoko IINO, Kazuyasu ...
Article type: Article
Session ID: 2353
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The gas velocity in the High-Velocity Oxy-Fuel (HVOF) process is highest in many types of thermal spraying process. Previous works show that the higher velocity of the coating particle seems to give high-quality coating. This paper analyzes the behavior of coating particle as well as the gas flow of inside the HVOF thermal spraying gun by using quasi-one-dimensional analysis. The effect of the nozzle shape on the particle velocity and temperature is examined.
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Kazuya SEO, Osamu KOBAYASHI, Masahide MURAKAMI
Article type: Article
Session ID: 2401
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The objective of this study is to reveal the initial condition of the optimal screw kick in rugby as well as the feature of that. A kick reaching touch safely gives a psychological boost to a team by relieving a period of pressure by the opposition. The objective here is to kick into touch safely, as well as to achieve maximum distance in the forward direction. Since there are two objective functions, this represents a multi-optimization problem. The optimization was carried out by using an elitist non-dominated sorting genetic algorithm. Distance achieved in flight is considered as an objective function, as well as the lateral deviation between the ball and the touchline. Six initial conditions ; these are the magnitude of the velocity vector, the flight path angle, the azimuth angle, the spin rate, the pitch angle and the yaw angle, were defined as control parameters. The results are summarized as follows: it is impossible for both objective functions to be satisfied simultaneously, although the largest value of distance achieved in flight and the smallest value of the lateral deviation between the ball and the touchline is the ideal situation. This kind of conflicting solution is called a "Pareto-optimal solution". The optimal kick in Pareto-optimal solutions made by the leg nearest the touchline produces a greater flight distance than the optimal kick in Pareto-optimal solutions made using the leg furthest from the touchline. The initial pitch angle, which is the angle between the longitudinal axis of the ball and the horizontal plane, should be comparable to or slightly greater than the initial flight path angle in order to satisfy the Pareto-optimal solutions.
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Naoko TAKAHASHI, Osamu KOBAYASHI
Article type: Article
Session ID: 2402
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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It has been observed in the wind tunnel test that a rugby ball, which can rotate freely in its short axis, starts auto-rotation when the ball is placed with the lace part against the wind tunnel flow ; the rotational speed increases rapidly to reach a constant rpm in a few seconds. The present work is intended to clarify the mechanism of the auto-rotation in the short axis of a rugby ball. In order to investigate the phenomenon, we have carried out wind tunnel tests involving measurement of rotational speed and aerodynamic forces, and flow visualization by oil flow. Experimental results reveal that the seam lines on the ball induce the boundary layer transition, and the resulting asymmetrical distribution of air pressure is attributable to the auto-rotation of the rugby ball.
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Takeshi ASAI, Kazuya SEO, Shinichirou ITO
Article type: Article
Session ID: 2403
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The purpose of this study is to visualize and analyze the vortex structure around the real flight soccer ball in high Reynolds number. In order to visualize the flow around the soccer ball during flight, a ball was coated as uniformly as possible with titanium tetrachloride. A subject then kicked the ball, and this activity was filmed at 4,500 fps with a high-speed video-tape recorder camera (Photron Ultima ; Photron Inc.). At an outside air speed of≤1.0m/s, the subject performed an almost non-spinning straight kick and a laterally spinning curved kick towards the middle of a goal from a distance of 15m. Images were recorded in black and white (256×256 pixels) and then uploaded onto a computer as AVI files. It seemed that the Strouhal number of wake near the real fright soccer ball was about 1.0 as similar as the high-mode value of a smooth sphere. It was observed that the vortex pairing in the wake.
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Kazuyuki Yamamoto, Taketo Mizota
Article type: Article
Session ID: 2404
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Wind tunnel experiments are conducted to measure aerodynamic side force and lift force acting on soccer ball with no rotation. TV image of the ball in flight shot by professional player in official soccer game is utilized to analyze movement of the ball. Free fall experiments of the ball are also projected to confirm the ball squeeze behavior using Aso-chouyou-brige.
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Akira OJIMA, Kyoji KAMEMOTO, Satoshi IDO, Toshiharu ARAI
Article type: Article
Session ID: 2405
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes a pioneering work of practical application of a vortex method in the field of fluid dynamics in sports science. The vortex method developed by the present authors is one of vortex element methods based on the Biot-Savart law, and it is known that the method provides a Lagrangian simulation of unsteady and vortical flows. -dimensional, complex and unsteady flows around an isolated sprinter were calculated. From the results of the present study, it has been confirmed that the vortex method is available and useful for research of the fluid dynamics in sports science.
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Shinichiro ITO
Article type: Article
Session ID: 2406
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Although the main propelling force is generated by a palm in swimming, it is greatly related to the characteristics of lift and drag forces of a palm. The characteristics change remarkablely, when the fingers of hand palm are opened or closed In this research, 3-dimensional velocity distribution was measured in the wake of hand palms by using X type hot wire probe. Furthermore, the author compared with the lift-drag characteristics of a delta wing analoguized with the configuration of hand palm to those of hand palms. It was shown clearly that hand palms have the similar characteristic in lift-drag specification and in the wake velocity distribution to a delta wing as 3-dimensional wings.
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Keiichi YAMADA, Kazuo MATSUUCHI, Takeo NOMURA, Jun SAKAKIBARA, Haruki ...
Article type: Article
Session ID: 2407
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Flow fields around a swimmer are extremely unsteady. Top swimmers are expected to swim using effectively unsteady flow force. A motion analysis can evaluate the unsteady motion of swimmer quantitatively. In addition, PIV (Particle Image Velocimetry) can visualize the unsteady flow field. With this method, the vortex motion around a hand can be evaluated quantitatively. Our study is to clarify the relationship between the vortex behavior and the motion of a hand in crawl swimming by using the motion analysis combined with PIV. The analysis is made for two subjects ; one is a male with no competitive career and the other a female Olympic swimmer. It was found that the hand motion in swimming was closely related to the vortex generation.
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Tadayuki HASHIZUME, Kazuo MATSUUCHI, Yoji NAKAZAWA, Takeo NOMURA, [in ...
Article type: Article
Session ID: 2408
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The shape of monofin and the properties of the material have not be optimized yet, because it is difficult to know the unsteady flow field and to relate it to the unsteady flow force. To develop the efficient monofin, we need to know the details of the flow field around monofin. For this purpose, we constructed a system for measuring flow field and flow force. The flow field was visualized using PIV (Particle Image Velocimetry). It is known that the vortex behavior plays an essential role in the generation of flow force. Therefore, our aim is to know the characteristics of flow fields. It was found that the flow field in the wake of monofin consists of two types of vortices ; one is wing-tip vortex and the other vortex shed at the top and bottom dead points. The latter is called the inverse Karman vortex street. Simplified 3D picture of the wake was obtained.
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Takashi GOTO, Yasuhiko OKUTSU, Yuuri TSUKIOKA, Yutaka OHTA, Eisuke OUT ...
Article type: Article
Session ID: 2409
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Improvement of aerodynamic performance and reduction of interaction tone noise of a centrifugal compressor with vaned diffusers are discussed by experiments, numerical simulation as well as visualization techniques using oil-film method. The focus of the research is concentrated on the pressure recovery characteristics within a vaned diffuser passage which is deeply influenced by diffuser vane geometries. By using the presented tapered diffuser vanes, a decrement of the pressure recovery characteristics occurred in the vicinity of the throat part of the diffuser passage can be successfully avoided, and also pressure drop due to the secondary flow recognized near the trailing edge of the diffuser vanes can also be suppressed. Furthermore, not only the sound pressure level of the interaction tone noise but also that of the broadband components can be attenuated effectively by using the tapered diffuser vanes.
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Daisaku SAKAGUCHI, Masahiro ISHIDA, Hiroshi HAYAMI, Yasutoshi SENOO, H ...
Article type: Article
Session ID: 2410
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In the present study, the diffuser performance and the sound pressure level were measured in a low specific type centrifugal blower with/without a low solidity cascade diffuser (LSD), and the frequency spectra were compared between the LSD and the vaneless diffuser. The flow behavior was also simulated _using a Navier-Stokes solver by ANSYS-CFX. The higher pressure rise in the diffuser was obtained by means of the LSD at the flow rates smaller than the design flow rate, however, noise level increased significantly at the off-design condition, comparing with the case of vaneless diffuser. It is found that the overall sound pressure level does not always increase by means of the LSD in the low flow rate range where the reverse flow induced by the LSD does not reach the impeller exit, on the other hand, the noise increases significantly when the reverse flow comes to the impeller exit. This noise increase is based on the broadband noise due to interaction between the reverse flow and the impeller, and also the discrete frequency noise defined by the cross product of the rotational speed of the impeller and the number of LSD.
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Taichi UTO, Souichi SASAKI, Yoshio KODAMA, Hidechito HAYASHI
Article type: Article
Session ID: 2411
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this study, influence of solidity on total pressure of a multiblade fan was analyzed. In the analytical theory, a pressure drop caused by a biased flow along the circumferential path of the impeller was proposed. The total pressure of the fan based on the theory could be estimated with a reasonable validity. When the solidity of the impeller was small, the total pressure of the fan became high. It was experimentally proved the influence of the slip factor on the total pressure of the fan was greater than the total fluid loss.
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Wei Sin SIM, Norimasa SHIOMI, Kenji KANEKO, Naoto SHIMOHARA, Toshiaki ...
Article type: Article
Session ID: 2412
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to clarify the behavior of tip leakage vortex in a semi-open axial fan, the experimental investigation was carried out using the Laser Doppler Velocimetery. Velocity vector maps were obtained at the blade rotor tip region and the pattern including tip leakage vortex were clarified As a result, it is found that the trace of tip leakage vortex changes as the fan loading changes. Furthermore, it is also found that the trace of tip leakage vortex changes as the tip clearance size changes.
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Kazuya TAKAHASHI, Masato FURUKAWA, Naofumi SAEKI
Article type: Article
Session ID: 2413
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Three-dimensional structure of vortical flow field has been investigated by numerical analysis on a half-ducted propeller fan. Complicated flow phenomena in the fan were captured by Reynolds-averaged Navier-Stokes flow simulation (RANS) and vortex structure identification based on the critical point theory. The tip leakage vortex starts to be formed near the blade mid-chord and grows nearly in the tangential direction, impinging on the pressure surface of the adjacent blade. In the blade passage, the breakdown inception of the tip leakage vortex occurs by interaction between the leading-edge separation vortex and the tip leakage vortex. It is expected that the behavior of the tip leakage vortex plays a major role in characteristics of the fan noise.
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Takahiro NISHIOKA, Toshio KANNO
Article type: Article
Session ID: 2414
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An experimental study has been carried out to clarify flow mechanism behind the modal-type stall inception. Pressure fluctuations on the casing wall showed that the interface between the incoming and tip clearance flows, which extends from the suction side near the rotor leading edge, disappears at the mid-passage at the stable operating points. This interface therefore does not become parallel to the leading edge plane. The rotor blade is overloaded, and the tip clearance backflow initiates from the rotor trailing edge when the tip incidence angle exceeds the critical value. The backflow extends upstream as the flow rate decreases, and the interface between the incoming and back flows becomes parallel to the leading edge plane at the stall inception point. We concluded from these results that the tip clearance-back flow from the trailing edge affects the modal-type stall inception.
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Sho BONKOHARA, Ken-ichiro IWAKIRI, Ryusuke OHTAGURO, Yasuhiro SHIBAMOT ...
Article type: Article
Session ID: 2415
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Effect of the tip clearance on the flow structure of rotating stall cell has been investigated experimentally in an axial flow compressor rotor. In the low-speed research compressor rotor tested, the number of multiple stall cells with short length-scale and the rotating speed change with the tip clearance. For two different tip clearances, the flow structure of rotating stall cell was analyzed by measuring the pressure distribution on the casing wall and the velocity distributions upstream and downstream of the rotor, using 'Synchronous Field Measurement' and 'Double Phase-Locked Averaging Technique'.
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Ken-ichiro IWAKIRI, Ryusuke OHTAGURO, Sho BONKOHARA, Yasuhiro SHIBAMOT ...
Article type: Article
Session ID: 2416
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Recently, it has been clarified that unsteady vortical flow field at rotating stall in an axial flow compressor rotor is subject to tornado-type separation vortex linking from the rotor blade suction surface to the casing wall by experimental fluid dynamics and computational fluid dynamics. With the growth of rotating stall, the tornado-type separation vortex rolls up to ahead of the rotor and the vortex leg moves to the midspan from the tip on the blade. Based on these features, the flow mechanism of rotating stall is explained by the three-dimensional separation vortex structure and its interaction with the casing wall and the blade surface.
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Yoichi KINOUE, Toshiaki SETOGUCHI, Norimasa SHIOMI, Kenji KANEKO
Article type: Article
Session ID: 2417
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The three-dimensional separation in a decelerating channel flow generated by the suction through a porous wall had been investigated experimentally. Unsteady characteristics of two corner separations were especially focused on. The value of cross-correlation function gets large negative values without any lag and the value of coherence gets peak value at around 0.5-2Hz. The corner separations near the top wall and near the bottom wall are not independent and keep coherent structure both with negative value of cross correlation function and with the frequency of around 0.5-2Hz.
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Ken-ichi FUNAZAKI, Kazutoyo YAMADA, Hideaki Sato, Mamoru KIKUCHI
Article type: Article
Session ID: 2418
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Three-dimensional unsteady aerodynamic interaction in a turbine stage, which has a great effect on aerodynamic stage performance, has attracted attention from researchers. To elucidate this effect, we have investigated the flow field by using high-precision three-dimensional Navier-Stokes solver ; where blade-count ratio is almost the same as that of a real turbine. Axial spacing between rotor and stator is changed. We have compared experimental timeaveraged pneumatic pressure data measured by five-hole pitot probe with numerical results.
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Hiroshi HAYAMI, Hideo TASHIRO, Makoto SAKAI, Shinichiro ARAMAKI
Article type: Article
Session ID: 2419
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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For a high-pressure-ratio centrifugal compressor, the behavior of shock waves should be clarified to improve its performance. In the present paper, the flow including shock waves at the inducer of impeller is simulated using a commercial CFD code. Regarding the relative flow Mach number contours at the inducer, the flow structure including shock waves is discussed. And the results are compared with the experimental results by PIV. And it is shown that the agreement is fair.
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Yuji TASAKA, Patrice Le Gal, Yasushi TAKEDA
Article type: Article
Session ID: 2420
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Flow between stationary and rotating disks, which is called as the tortional Couette flow, was investigated experimentally as a family of Couette flow including Taylor-Couette flow. Behavior of turbulent spot appearing in the flow was observed and its shape, similar to hose-shoe vortex appearing in the turbulent boundary layer, convection and disappearance were explained from the obtained images visualized by Kalliroscope flakes. Statistical analysis to determine the stability curve for the spot was performed based on visualized images. Using image analysis, the number of spot at each radius was counted as the number of black pixels for several rotating speed. Probability distribution for spot existing determined form the obtained number has similar form with the mathematical model constructed under some assumptions.
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Nao NINOMIYA, Kazuhiro YAMAMOTO
Article type: Article
Session ID: 2421
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Although the spark tracing method is one of the most classical techniques of flow visualization, the measurement by this technique has been limited to a qualitative observation or to one-dimensional velocity measurement. Recently, the authors of this study have been succeeded in measuring the two-dimensional velocity field by applying the dynamic programming matching technique, which has commonly been used in the voice recognition, to the images obtain by the spark tracing. In order to increase the accuracy of this technique, the powder of aluminum oxide, which shows the radiant trails while they are burned by sparks, has been introduced to the flow. Presently, color information of the sparks is incorporated to the DP matching method and the well-known turbulent velocity field of an axisymmetric free jet is measured.
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Nobuyuki ISOSHIMA, Takayuki FUJIMOTO, Yukinobu Abe, Masatoshi WATANABE ...
Article type: Article
Session ID: 2422
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A system of numerical flow simulation with an automated mesh generator and parallelized solver was developed and applied to the flow-field inside an optical disc drive. In this simulation system, a uniformly spaced Cartesian grid is used to reduce time and automatically generate a mesh from CAD data for complicated geometries, such as optical disc drives. The simulation results of optical disc drives are validated by particle image velocimetry (PIV) and pressure-distribution measurements. The measured velocity distributions above a rotating disc and around a pick-up unit show quantitative agreement with the simulated distributions. For the pressure distributions on a top case of an optical disc drive, although there is an error of 10Pa between simulated and measured results, the position of the peaks and distribution of pressure show good agreement. Comparing both sets of measurements, the simulation results in a Cartesian grid system are sufficiently accurate to enable the flow-field to be quantitatively assessed.
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Tadatsugu YOSHIDA
Article type: Article
Session ID: 2423
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The CFD numerical solution method for improving the convergency of solver with an incomplete pretreatment is described in this paper. It is shown that the reduction effect of fill in by the ordering method of NO, RCM, and NDO are first compared with the easy mesh, and NDO is excellent. Next, convergent aggravation is controlled in the plastic processing analysis that applied the ICCG method to the NDO mesh by the two step meshing method. The convergent improvement method by optimization of fill in processing of the NDO+ICCG method is proposed to the SIMPLE scheme.
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Masahiro OGIWARA, Eiji EJIRI
Article type: Article
Session ID: 2424
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Flows around the stator of a torque converter for automobiles were investigated using a general purpose CFD code. The complicated separated flows in the lower speed ratio range were computed with the k-ε model and some other deviation models. The flow measurement using PIV system was also conducted in order to evaluate the accuracy of the computed results. The results showed the low Reynolds number type second-order non-linear k-ε model gave the closest result to the measured results. The standard k-ε model was not suited for such a complicated flow as the case. The results also confirmed that the exit flow angle decreased as the inlet flow angle excessively increased.
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Koki WACHI, Tsuneaki FUJII, Yuji NAKANISHI
Article type: Article
Session ID: 2425
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The flow in a stationary Pelton bucket is simulated by a Moving-Particle Semi-Implicit Method (MPS). The bucket is set at three angular positions so that different inlet conditions can be imposed. In the MPS method, the solid wall of the bucket has to be represented by the same calculation particles as the particles for fluid, though a Pelton bucket has complicated 3D shape. Therefore, a simple method arranging the wall particles is proposed. The particle and pressure distributions on the bucket are presented in this paper.
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Michihiro NISHI, Kouichi YOSHIDA, Tomoaki MARUMO
Article type: Article
Session ID: 2426
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In micro hydro-turbine systems, there are cases to adopt a siphon pipe for the penstock to reduce the construction cost. And it has the feature that the flow in the pipe is easy to stop at the load rejection of a hydro-turbine by using the natural air admission. However, few works have been made to investigate siphon phenomena. Thus, the present experimental study is aimed to make clear the effect of admitted air on the flow in a siphon-pipe. To clarify the transient phenomena from the beginning of air admission to the shut-off of the flow, water and air flow rates, wall pressure near the air port in a siphon-pipe (50mm in dia.) were measured. Flow visualization was also made to see the flow behavior, which was taken from outside by a CCD camera. Based on the dimensional consideration applied to the experimental data, correlation to specify the required time for shut-off has been made.
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Takuya OSHIKAWA, Koji KURACHI, Hiroshi TSUKAMOTO, Koji MIYAZAKI
Article type: Article
Session ID: 2427
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Numerical calculations were carried out on unsteady flows in a pump sump with a cylindrical suction pipe using a commercial CFD code (CFX-10.0) in order to investigate the mechanism of the air-entraining vortex generation. The calculated results show that the dimple generated behind a suction pipe moves to the downstream with growing up, and the air-entraining vortices generated when the dimple reaches the vortex from a suction pipe. The calculated geometry of water surface in a pump sump near a suction pipe was compared with one measured by moire method. The dimple on the surface behind the suction pipe was found to grow up to the air-entraining vortex. The measured and calculated results agree well. As a result of the present study, it was found that mechanism of the entraining-vortex generation can be captured by CFD.
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Takanao KIMURA, Junichi NAKAO, Akimamo KAWAHARA, Michio SADATOMI
Article type: Article
Session ID: 2428
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The sediment of dead leaves, the earth and sand cause the decrease in pondages and the water pollution in the lake or sea. To remove such sediments, an air lift pump attracts attention because it is hard to occlude by its simple structure. The bubble-jet-type air lift pump developed by Sadatomi can remove sediments which traditional air lift pump couldn't remove. The bubble jet generator which was also developed by Sadatomi is used in the bubble-jet-type air lift pump as an air supply. Using the bubble jet generator, it can forcibly levitate sludge accumulating on the bottom of lake or sea. Our purpose is to improve water quality and to increase the pondage with the bubble-jet-type air lift pump. In this paper, experimental results on the performance of the bubble-jet-type air lift pump are mainly reported.
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Kyota SHIRASAWA, Akinori FURUKAWA, Satoshi WATANABE, Kusuo OKUMA, Toru ...
Article type: Article
Session ID: 2429
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The adoption of contra-rotating rotor has been proposed in response to a demand for the higher specific speed of axial flow pump. The internal flow field and blade rows interactions between the front and rear rotors should be considered in the design for higher performance and more stable operation. Then for more understanding of the internal flow of contra-rotating axial flow pump, the flow fields have been measured at various flow rates with Laser Doppler Velocimetry. In the present paper, measured flow fields between front and rear rotors at the design flow rate are shown and the flow behavior is discussed with the velocity vector distributions in the relative reference frames with front and rear rotors.
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Masahiro MIYABE, Akinori FURUKAWA, Hideaki MAEDA, Isamu UMEKI, Yoshino ...
Article type: Article
Session ID: 2430
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper presents the unsteady internal flow in a mixed-flow pump with a vaned diffuser. Tested pump has a positive slope of the head-flow performance curve at about 65% flow rate of the best efficiency point due to rotating stall in the vaned diffuser. In order to investigate this phenomenon, pressure fluctuation measurements and dynamic PIV measurements have been performed. It is found that the strong vortex develops at the leading edge of the diffuser vane and backflow from the outlet of the diffuser vane is induced and then the backflow conflicts against the outward flow from the impeller. As the result, the periodical unsteady flow is obtained. Based on PIV pictures, it is clarified that a stall occupies four passages (backflow area is three-passage and the stall core occupies one-passage) out of thirteen passages.
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Naoki MATSUSHITA, Kusuo OKUMA, Satoshi WATANABE, Akinori FURUKAWA
Article type: Article
Session ID: 2431
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Centrifugal pumps have been utilized in various industrial fields with the diversification of applications and operating fluids due to the simple structure and the easy maintenance. A centrifugal pump with tandem arrangement of double rotating cascades and stationary cascade downstream of the impeller has been confirmed as a preferable structure for air-water two-phase flow pump. In this case, the smaller impeller yields lower pump head in single-phase flow, without increasing the rotational speed. Therefore, it might be desired to install other devices, instead of vaned diffuser (stationary cascade), downstream of the larger impeller if two-phase flow performance would be improved under the restricted pump size. In the present study, a double volute passage is focused downstream of larger impeller consisting of tandem arrangement of rotating cascades. Then its effects on two-phase flow performances are experimentally examined. The guiding principles of selecting a preferable diffuser structure on designing a air-water two-phase flow centrifugal pump with higher performance are discussed in comparison with case of vaned diffuser downstream of smaller impeller.
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Jun MATSUI, Junichi KUROKAWA, Kouichi NISHINO, Young-Do Choi, Kouichi ...
Article type: Article
Session ID: 2432
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The internal flow in the centrifugal pump with a circular casing is measured by PIV method. The casing and impeller of semi-open type have two-dimensional shapes. The type number of the pump is 2.44×10^<-1> and specific speed is 100[m, m^3/min, min^<-1>]. The unsteady flow near the exhaust tongue is measured mainly. Even at the best efficiency point, the flow around the impeller is not symmetric. The radial velocity is remarkable only at the exhaust area of the casing. The flow near the impeller blade changed dynamically according to the relative position of the tongue.
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Ryunosuke Kawashima, Mitsuo Uno, Daisuke Yonekura
Article type: Article
Session ID: 2433
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The shaft-less centrifugal pump was developed based on the magnetic inductive system. The main feature is no shaft and floating impeller rotates in an independent condition because of bearing less and seal less structure. However, in low flow condition, the floating impeller rotate in instable condition. And, it was because of pressure fluctuatuon in internal flow. On the other hand, J-grooves is developed by KROKAWA for the purpose of improvement in unstable phenomena of mixes tuebo machine. It was reported that J-grooves was affect the internal pressure field. In this paper, we tried to control impeller attitude by use of J-grooves. Furthermore, the pump performance and floating condition of impeller were measured in ordre to make clear the effects of J-grove casing treatment on the shaft-less centrifugal pump.
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Noriaki NAKAMURA, Syuusuke HORI, Tomoyuki HASHIMOTO, Mitsuru SHIMAGAKI ...
Article type: Article
Session ID: 2434
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Casing treatment with an aim for the suppression of cavitation surge was experimented. For the investigation of internal flow, the observations of cavitation phenomena with stroboscope were conducted. FFT analysis showed that weak cavitation surge appeared at low cavitation numbers. However, the peak of the cavitation surge became lower level using the casing treatment. In addition, suction performance did not gradually increase, i.e., dynamic gain was almost flat.
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Mitsuru Shimagaki, Tomoyuki Hashimoto, Satoshi Hasegawa, Noriaki Nakam ...
Article type: Article
Session ID: 2435
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Casing treatment with an aim for the suppression of cavitation surge was experimented. For the investigation of internal flow, the observations were conducted with PIV. It was found that (a) the strength of the backflow becomes weaker than that without casing treatment, (b) unsteadiness of the backflow of inducer is remarkable.
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