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Article type: Appendix
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Article type: Appendix
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Article type: Index
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Masaru USAMI, Keisuke MIZUGUCHI
Article type: Article
Session ID: 1425
Published: September 04, 2004
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The new intermolecular collision scheme is developed to obtain an excellent result even if cells are lengthened in the 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 flowfield are in local equilibrium with some temperature and flow velocity: The new collision scheme is applied to a supersonic free jet and a steady vortex behind an inclined flat plate, and its effect is confirmed. The new collision scheme is also verified effective for unsteady flows such as vortex shedding.
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Hideki Takeuchi, Kyoji Yamamoto, Toru Hyakutake
Article type: Article
Session ID: 1426
Published: September 04, 2004
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The Poiseuille flow and thermal creep flow of a rarefied gas through,a grooved, duct are investigated on the basis of the B-G-K equation for all range of the Knudsen number. The discrete ordinate method is used for numerical calculation. The flow velocity distribution as well as the flow rate per unit area is obtained. The flow rate of the Poiseuille flow suffers a remakable effect by the groove when Knudsen number is small.
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Gou FUKANO, Masahiko SHIBAHARA, Masashi KATSUKI
Article type: Article
Session ID: 1427
Published: September 04, 2004
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Toru HYAKUTAKE, Kyoji YAMAMOTO, Hideki TAKEUCHI
Article type: Article
Session ID: 1428
Published: September 04, 2004
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To investigate flow of gas mixture through micro channel accurately, we have determined the accommodation coefficients of each species (argon and xenon) for gaseous mixtures by combining -MD and DSMC simulation. These obtained accommodation coefficients were applied for the flow simulation of gas mixture in micro channel, and influence of the surface with adsorbates on the flux rates was investigated. The simulation results show that velocity slip and accommodation coefficients for gas mixtures differ from that for a single gas. The differences of the molar concentration and wall characteristics lead to the variations of the flux rates in the channel.
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Masahiko SHIBAHARA, Tomoaki KUNUGI, Katsumi MUKO, Masashi KATSUKI
Article type: Article
Session ID: 1429
Published: September 04, 2004
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Energy transfer from fluid to the surface was calculated by using the classical molecular dynamics method in order to investigate effects of surface structures in nanometer scale on the surface energy transfer numerically. Surface structures on the constant surface area were composed of several hundred atoms having the same thermal properties. Upper region in the, calculation domain was controlled at a constant temperature and the solid atomic layer at lower region was controlled at a constant temperature so as to, make a temperature gradient in the calculation system. Fluid molecular diffusion in the vicinity of the surface was dependent on the surface structures in nanometer scale that affected the dynamic behaviors of fluid molecules in the vicinity of the surface.
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Kenichi NANBU, Yohei Hareyama, Shigeru KANEMOTO
Article type: Article
Session ID: 1430
Published: September 04, 2004
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Cost of disposing nuclear waste greatly depends on the level of radioactivity we are developing a system for measureing the level. In this system a-radioactivity is determined by measuring the amount of ion ionized by a-ray transported by the flow of air. Transport and diffusion characterization of much ions are examined using the test-particle Monte Carlo method.
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Kenichi NANBU, Takaaki FURUBAYASHI
Article type: Article
Session ID: 1431
Published: September 04, 2004
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Plasma etching is a typical technique in materials processing. Radicals resulting from electron-molecule collisions play a crucial rule in the etching. The production rate of radicals is governed by the electron energy distribution function(EEDF). Effect of electron-electron collision in the EEDF's is examined using Bobylev and Nanbu's theory (Phys.Rev.E, Vol.61(2000),4576-4586)
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Kenichi NANBU, Tatsuhiro ODA
Article type: Article
Session ID: 1432
Published: September 04, 2004
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Plasma processing such as etching, surface treatment, and thin film deposition is widely known as representative applications of nonequilibrium plasmas. A typical size of plasma reactors for conventional use is a few tens centimeter. Recently; microplasmas with the size of several mm to several μm have attracted the attention. The microplasmas have the advantage that such a plasma is generated in a required place with a required volume. When the size of the plasma becomes very small, new aspects of plasma physics may appear that we not considered in the conventional plasmas. The microplasmas are studied using the particle modeling and the structure of microplasmas are examined.
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Hideto TAKEKIDA, Kenichi NANBU
Article type: Article
Session ID: 1433
Published: September 04, 2004
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The Particle-in-Cell/Monte Carlo (PIC/MC) code for 2-dimensional axisymmetrical argon plasmas is developed and applied to 1-turn inductively-coupled argon discharges. Here are clarified the effects of non collisional heating on the plasma density.
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Masakazu Fukushima, Mitsuhiro MATSUMOTO
Article type: Article
Session ID: 1434
Published: September 04, 2004
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In order to investigate combustion processes in fuel gas and in fuel liquid droplet systems, molecular dynamics simulations were carried out with a simple particle model for combustion. After giving sufficient kinetic energy into a small region, one dimensional flame propagation and the interaction between the flame and a liquid droplet were observed.
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Kenichi NANBU, Toshihiko OTSUKA
Article type: Article
Session ID: 1435
Published: September 04, 2004
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The motion of nanoparticles in gas flows of SiH_4 and H_2 is examined for a CVD(chmical vapor deposition) reactor. The objective is to study the effect of particle size, gas pressure, and mass flow rate on the flux of nanoparticle sticked to the a-Si:H film. DSMC is used in the simulation.
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Katsuhiro SHIRONO, Hirofumi DAIGUJI
Article type: Article
Session ID: 1436
Published: September 04, 2004
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Molecular Dynamics (MD) simulations of hydrated zeolite NaX (Si/A1=1.0) and NaY (Si/A1=2.0) were done at. a temperature of 300 K. The variable, partial charge model of water molecules (SPC-FQ) were used and the effects of the dipole moments on the differential heat of adsorption and diffusion coefficient. The distributions of water molecules in a supercage of zeolites NaX and NaY were similar to those calcualted with the fixed charge model(SPC/E). However, from the low hydration state to the middle hydration state, the dipole moments were smaller than that of liquid water. The differential heats of adsorption calculated with this model-were in good agreement with the experimental values, but the dynamical properties,such as diffusion coefficients of adsorbed water molecules were not improved.
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Takayoshi INOUE, Keisuke IMAI
Article type: Article
Session ID: 1437
Published: September 04, 2004
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As CO poisoning problem has been of great importance for DMFC and methanol synthesis process, CO behavior on Pt surface was studied using DFT method. At first, effects of a surface step on, adsorbed CO on Platinum were studied, and it was clarified that CO tends to adsorb on an edge of step about 7% stronger than on a completely flat surface. As in DMFC, OH produced on Ru removes adsorbed CO on Pt through a oxidation reaction, this reaction on a flat surface and at a surface step were studied. The results show that with Ru allocated in a step comer, an energy barrier for the reaction is smaller than that on a flat surface.
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Masahiro OTA, M. Ferdows
Article type: Article
Session ID: 1438
Published: September 04, 2004
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In order to perform the thermal properties of CO_2 hydrate Monte Carlo simulations have been carried out under constant temperature and pressure conditions. In this paper we discussed two kind of thermal properties like as density and specific heat at constant pressure. The thermal properties have been focused for the clathrate hydrate of CO_2 at temperatures ranging from 150 to 280 [K] and pressure up to 50 [Mpa] in the NPT ensemble using TIP4P effective intermolecular potential model of water. Our results indicated that density depend on the rate of filling factor, on the contrary, specific heat at constant pressure do not receive pressure effect at the same rate of filling condition. Comparisons between MC calculated result and experimental results also are presented.
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Hiroki YAMAGUCHI, Shu TAKAGI, Yoichiro MATSUMOTO
Article type: Article
Session ID: 1439
Published: September 04, 2004
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The direct simulation Monte Carlo (DSMC) method is widely used for simulations of rarefied gas flows. Collisions of diatomic molecules have been investigated, numerically in order to make a vibrational relaxation model of diatomic molecules for the DSMC method. The collision cross section for vibrational relaxation was described as a function of the relative translational, the rotational and the vibrational energies of the colliding molecules. Thus the collision cross section was evaluated with the Monte Carlo integration for these parameters. A collision was simulated with the Semiclassical approach in which the vibrational motion was treated quantum mechanically and the rotational and the relative translational ones are treated classically. The transition rate coefficients agreed well with former researches. The collision cross section for the collinear collision was modeled as a function of the relative translational energy of the colliding pair.
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Yukinori SAKIYAMA, Shu TAKAGI, Yoichiro MATSUMOTO
Article type: Article
Session ID: 1440
Published: September 04, 2004
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According to the recent development of the ab initio calculation method, the various macro-scale phenomena can be obtained from micro-scale mechanics, such as the electronic states. In this study, we constructed the new pair potential model of SiH_4 (silane) molecules that is one of the most popular species in semiconductor manufacturing processes. But only the limited transport properties are obtained by experiments because of its explosive nature. In this study, potential parameters of Si-Si, Si-H and H-H interaction for rigid silane molecules were obtained by molecular orbital calculations. And the various transport phenomena were calculated from molecular dynamics simulation with the new potential model.
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Hiroaki MATSUMOTO, Kiyotaka KOYAMA
Article type: Article
Session ID: 1441
Published: September 04, 2004
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The rotational energy gain function for diatomic molecule, which is defined as the mean rotational energy gain per collision per molecule without pre-collision rotational energy, is examined by the Monte Carlo integration combined with the classical trajectory calculation using the diatomic Lennard-Jones potential, and then compared with the Parker s approximate theory. If is demonstrated that the calculated energy gain function is reasonable agreement with that of Parker s expression for the translational energy range E/ε_<LJ>≥10 and smaller than Parker s expression for E/ε_<LJ>≤10, and simulated rotational collision number is smaller than Parker s expression.
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Hideo MORI, Tomohide NIIMI, Isao AKIYAMA, Takumi TSUZUKI
Article type: Article
Session ID: 1442
Published: September 04, 2004
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The rotational nonequilibrium along the centerline of supersonic free molecular flows of nitrogen, is analyzed, measuring the rotational energy distribution by REMPI. As a result, the rotational temperatures obtained from the Boltzmann plot using small rotational quantum numbers coincide with the Marrone's data obtained by electron beam flourescence technique. However, a straight line cannot fit all data points, especially at large rotational quautum numbers. This means that the rotational nonequilibrium occurs in the rotational energy distribution, that is, the rotational temperature cannot be defined. The transition of the rotational nonequilibrium phenomena is also discussed by showing the dependence of the rotational energy distribution on the distance from the nozzle exit in the flows.
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Hideo MORI, Tomohide NIIMI, Yusuke OSHIMA, Madoka HIRAKO, Hiroyuki UEN ...
Article type: Article
Session ID: 1443
Published: September 04, 2004
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The pressure sensitive paint (PSP) technique has the capability to be applied to high Knudsen number flows, such as low density gas flows, micro-flows, and so on. In this study, to inspect the feasibility of PSP for measurement of pressure on a solid surface in high Knudsen number flows, fundamental properties of three PSPs [PdTFPP, PdOEP and PtTFPP bound by poly(TMSP)] are examined, especially in the range of pressure below. 1-30Pa (about 1 Torr). As an application of PSP to low density, gas flows, we also measure the pressure distribution on a jet-impinging solid surface successfully, using PdOEP/poly(TMSP) with extremely high pressure sensitivity.
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Kenichi FUNAMOTO, Toshiyuki HAYASE, Yoshifumi SAIJO, Tomoyuki YAMBE
Article type: Article
Session ID: 1524
Published: September 04, 2004
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In order to reproduce the blood velocity and pressure fields of the blood flow for an accurate diagnosis or treatment for serious circulatory diseases such as aortic aneurysms, we are developing a new analysis methodology, namely Ultrasonic-Measurement-Integrated (UMI) simulation, by integrating color Doppler ultrasonography and numerical simulation. In the UMI simulation, feedback signals are added to the governing equations to compensate for the difference between computation and measurement. In this paper, we perform UMI simulation for the blood flow in descending aorta with an aneurysm. It is revealed that the UMI simulation reproduces the complicated blood flow structure and detects the incorrect measurement data.
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Takashi WATANABE, Takashi MORISUE, Ikuo NAKAMURA
Article type: Article
Session ID: 1525
Published: September 04, 2004
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Flows developing around a rotating disk in a cylindrical enclosure were investigated by a three-dimensional numerical Flows developing around a rotating disk in a cylindrical enclosure were investigated by a three-dimensional numerical method and experimental observations. The thickness of the disk, the height of the enclosure and the radii of the disk and the inner wall of the enclosure are finite, and the gap width between the disk rim and the enclosure is not negligible. In the gap, a vortical flow is induced by the centrifugal effect. When the gap width is small, the basic flow, spiral rolls and turbulent spirals apper as the increase in, the Reynolds number, as can be seen in the case,where the gap width is almost zero. In the system with larger gap width, the flow changes directly from the basic flow to the turbulent spirals, and no flow with spiral rolls apperes. The flow patterns predicted by the numerical, method accord with those found found by the experiment observations.
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W. Zhao, T. Saito, K. Horie, H. Ojima, K. Takayama
Article type: Article
Session ID: 1526
Published: September 04, 2004
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The pressure wave refrigerator (PWR) is the wave-machine to refrigerate the gas with intermittent expansion waves. Due to the simple structure. and robustness, PWR may have many potential applications if the efficiency becomes competitive with the existing alternative devices. In order to study deeply the mechanism in PWR and practice an industry utilizing, a unique compact PWR facility was set up in SWRC, Institute of Fluid Science, Tohoku University. The performance of the PWR facility is evaluated and the effect of major operation parameters, such as the rotational rate of gas distributor, the length of expansion tubes and some configuration parameters are discussed in the paper Some theoretical considerations to improve the PWR efficiency are also given.
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Kazuya SEO, Osamu KOBAYASHI, Shingo SAKAMOTO, Masahide MURAKAMI
Article type: Article
Session ID: 1527
Published: September 04, 2004
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This paper describes the aerodynamic characteristics of a rugby ball as well as its unpredictable flight trajectory. Wind tunnel tests with a full size model were carried out to measure the aerodynamic forces on a spinning rugby football as well as those on a non-spinning ball. It was found that the side force coefficient depends on the seam position except for an angle of attack of 0° in the case of a non-spinning ball. The simulated flight trajectory of the ball with lower spin rate fluctuates irregularly in the lateral direction, while the trajectory with higher spin rate moves monotonically in the lateral direction.
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Viren Menezes, T. Saito, T. Kuribayashi, M. Sun, K. Takayarna
Article type: Article
Session ID: 1528
Published: September 04, 2004
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Shock wave reflections over large apex angle cones have been investigated in a diaphragm-less shock tube with an intention of studying the phenomenon of transition from regular to Mach reflection over the cone surface. It is believed that over large angle cones with semi-apex angles ranging from 43 to 48 degrees, the reflection of an incident shock wave at a moderate Mach number of 2.38 may undergo a transition from regular to Mach over the cone surface due to viscous effects. The experiments are carried out with two test gases, nitrogen and argon. Flow visualization experiments are planned to study this phenomenon in detail over cones of different apex angles in the above range. Measurement of surface heat flux using platinum thin film sensors has also be carried out in order to analyze the heat transfer history over the cone surface during these reflection phenomena. The experimental results have been compared with the numerical results obtained from a commercial N-S solver Fluent (Version 6.1, Fluent Inc.). The experimental results obtained in this study are expected to be useful in validating CFD codes.
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Hiroshi MAITA, Takahiro WATANABE, Seiichiro IZAWA, Ao-kui XIONG, Yu FU ...
Article type: Article
Session ID: 1529
Published: September 04, 2004
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The aerodynamic noise generated from a laminar separating flow over a cavity is passively controlled by a plate inserted into the cavity. Compared with the turbulent flow case, the noise reduction effect becomes smaller and in particular, the cavity noise increases near the leading edge region. It is also found that the dominant frequency of the noise shifts depending on the location of the plate.
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Yoshifumi YOKOI, Susumu INAGAKI
Article type: Article
Session ID: 1530
Published: September 04, 2004
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In this study, in order to examine the noise measurement technique of the internal flow, the flow noise due to vortex shedding from a circular cylinder was measured by use of a suction type wind tunnel which was equipped with glass wool walls and a condenser microphone. As a result of experiments, it was confirmed that the operation noise of the blower was sufficiently cut off. In case of the glass wool wall, the uniformity of flow distribution was good but the thickness of the boundary layer became thick. The directivity of both of the source and the microphone did not influence a measurement result in the experiment range. It was proved that the microphone was measuring a fluid noise by the fluid vibration which was based on the Karman vortex shedding. It was obtained that this measurement technique was suitable for the fluid noise measurement of the internal flow.
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Akiyoshi IIDA, Hiroyuki TANIDA, Akisato MIZUNO
Article type: Article
Session ID: 1531
Published: September 04, 2004
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In order to control the aerodynamic noise radiated form bluff bodies, vorticity structures and flow field around a rotating circular cylinder at Reynolds numbers between 10^2 and 10^4 were numerically simulated. Aerodynamic force and resultant aerodynamic noise is drastically changed with the ratio of the uniform velocity and the rotational velocity of the cylinder. At low velocity ratio, anti-symmetric vorticity structures are generated behind the cylinder and lift-drag ratio is rapidly increasing. On the other hand, an absolute value of lift-drag ratio is reducing over the velocity ratio of 2. As a result, aerodynamic forces turn weakness and the resulting aerodynamic sound becomes small. The noise level of the rotational cylinder is 10 dB lower than that of the conventional circular cylinder.
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Masashi SANO, Takeshi OYAIZU
Article type: Article
Session ID: 1532
Published: September 04, 2004
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Experimental investigations of the generation of resonant sound by flow in a duct containing two orifice plates were performed. The frequencies of sound were examined in detail when the velocity was increased from 3 to 30 m/s. In order to calculate the convective speed of vortices formed between the two plates, the measurements of the phase of fluctuating velocity were made using a hot-wire anemometer. The vortex shedding frequencies are loced-in the pipe modes and frequency jumps from one mode to another are observed It was found that the phase velocity of the vortices varies from 0.55 to 0.62 U_<max> where U_<max> is the uniform velocity of the jet.
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Hiroki MATSUMOTO, Ken-ichi SAITOH, Naoto SUZUKI
Article type: Article
Session ID: 1533
Published: September 04, 2004
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This paper deals experimentally with aerodynamic sound generated by an elastically supported circular cylinder in a uniform air-flow. The circular cylinder is supported by two. plate springs-at both ends. The air-flow induces vibrations on the circular cylinder and generates aerodynamic sounds. In the experiment, the frequency spectra of cylinder vibration and radiated sound are analyzed. As a result, it becomes clear that the sound generated from the elastically supported circular cylinder is larger than the sound from the fixed one, when the frequency of Karman vortex agrees with the natural frequency of the circular cylinder.
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Mitsuru IKEDA, Kiyoshi NAGAKURA, Yukie OGATA
Article type: Article
Session ID: 1534
Published: September 04, 2004
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The pantograph noise of Shinkansen train-sets consists of aerodynamic noise, sliding noise, and arcing noise. In order to reduce pantograph noise effectively, it is important to estimate the contributions of each noise. However, it is difficult to estimate sliding noise in high-speed operation because sliding noise and aerodynamic noise are mainly generated from a same member, or the panhead. In this-study, the authors estimated contribution of sliding noise by comparing the pantograph noise when it is not sliding on contact wire and that when it is. The experimental result shows that the sliding noise is sufficient lower than aerodynamic noise in the case of a low aerodynamic noise pantograph.
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Daisuke SUZUKI, Kensaku YANAGIMOTO, Seiji WATANABE, Hikaru TAKAHASHI
Article type: Article
Session ID: 1535
Published: September 04, 2004
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In active noise control, extension of an effective frequency range and silent sound field are realized by compound with a slit resonator and speakers (active sound sources). Then, this research performed numerical sound analysis by the indirect boundary element method about the sound characteristic of the circular slit, resonator, elliptic slit resonator and cross slit resonator equipped the active sound sources. Consequently, the result of the radiation sound pressure of an experimental value and a simulation was comparatively well in agreement. Moreover, it was cleared that the sound characteristic radiated from elliptic slit and cross slit showed good performance.
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Shigeru SATO, Motoki WAKASUGI, Kensaku YANAGIMOTO, Masayuki TAKAHASHI
Article type: Article
Session ID: 1536
Published: September 04, 2004
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Defective products diagnosis in a micro DC fan's assembly line is performed using man's hearing. However, since this requires skill and also arise individual difference, exact judgment is difficult for it. Moreover, the background noise reduces diagnostic accuracy, and the measure against the improvement in a SIN ratio of the detected sound signal is needed. Then, this research performed improvement in a SIN ratio in sound diagnosis of a micro DC fan using Adaptive Line Enhancer (ALE). Consequently, the noise signal be not correlative in time decreased by-about 10dB, the periodic signal with high correlation was acquired as an output signal, and it was cleared that this periodic signal could be used for unusual diagnosis.
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Takashi ESAKI, Masato MIKAMI, Naoya KOJIMA, Yuya IMAGAWA
Article type: Article
Session ID: 1537
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The flow-induced noise was experimentally studied for sudden expansion pipes with low Mach number flow (0.1<M<0.2). The results showed that the sound pressure level of the flow induced noise for a sudden expansion pipe was larger than that for a straight pipe and was almost independent of the expansion angle within the range from 15 to 90 degrees. The sound power was proportional to the sixth power of the inlet flow velocity for sudden expansion pipes. This fact shows that the noise source was acoustic dipoles generated by the pressure fluctuation acting on the inner wall downstream of the sudden expansion. The sound power of the flow-induced noise decreased with the expansion pipe length. The reduction effect of the flow-induced noise was attained by the reduction of the fluid collision on the wall. The turbulence was generated by the jet flow in the expansion pipe and the turbulence intensity was smaller with shorter expansion length.
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Kunisato SETO, Khan Md Tawhidul Islam, Zhixian XU, Hiromitsu OHTA, Ala ...
Article type: Article
Session ID: 1538
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Experiments were cameo out to control the screech tone generated from a supersonic jet by using a spherical reflector. The reflector was placed at the nozzle exit which minimized the sound pressure at the exit region. The weak sound pressure did not excite the unstable disturbances at the exit and thus the loop of the feedback mechanism could not be accomplished and the jet screech was eliminated. Experimental results indicate that the new system suppresses not only the screech tones but also the broadband noise components and reduces the overall sound pressure level of the jet. A good performance in controlling jet noise was found as the reflector was placed at the nozzle exit; however, the position of the reflector was changed to the upstream direction for improving the performance of jet screech cancellation at high pressure ratio and found good result.
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Michihisa TSUTAHARA, Takeshi KATAOKA, Akinori TAMURA, Kenji SHIKATA
Article type: Article
Session ID: 1539
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Two-dimensional direct numerical simulation of the edge-tones by the finite difference lattice Boltzmann method (FDLBM)is reported. We use anew lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted coordinates. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. It is clarified that the sound wave generated in rather wide region and. individual vortices do not affect the sound wave propagation. We showed that the frequency of edge-tones depend on the jet flow speed.
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Nobuhiro YAMAZAKI, Kiyoshi NAGAKURA, Mitsuru IKEDA, Akio SAGAWA
Article type: Article
Session ID: 1540
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The aim of the present work is to locate the aeroacoustic sources of pantograph in a Closed Wind Tunnel Test Section by using 2-D microphone arrays. It is essential to reduce the flow-induced self-noise of array microphones for accurate measurement of acoustic signal. In order to reduce the un-correlated noise received by each microphone, the method of calculating cross spectrum of the outputs from 2 pairs of 2-D microphone arrays is applied. Furthermore, surfaces of the microphones were covered with thin films to suppress boundary layer noise. The cross spectrum method was validated basically by speaker tests using white noise. Then these techniques were applied to wind tunnel tests on a pantograph model. Major acoustic sources such as panhead, were identified at 60m/s.
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Riho HIRAMOTO, Kuniaki TOYODA, Hisashi KOGAWA
Article type: Article
Session ID: 1541
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Investigation of sound source in a flow separated from a sharp edged fence was discussed by simultaneous measurements of fluctuating static-pressure and aerodynamic sound. Sound source terms of Ribner's Dilatation theory were calculated with measured fluctuating static-pressure, and intensity of the sound source term, spectra, coherence and integral of coherent output power of aerodynamic sound and sound source term-were-discussed to determine flow regions contributing to aerodynamic sound generation. The results suggest that the separated shear layer contributes to a broaden. spectrum generation of aerodynamic sound, in particular a region clear the edge of the fence shows maximum contribution even though there is not outstanding characteristics in coherence.
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Toshifumi KUDO, Tetsuo TOMINAGA, Tsuyoshi EGUCHI, Atsushi SUZUKI
Article type: Article
Session ID: 1542
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Recently, as the noise of the automobile is decreasing, a radiator fan included in it is also needed to be quiet. However, the noise of the radiator fan is mainly aero-dynamic noise around fan blades, generally called BPF (Blade Passing Frequency) noise, and it is easy to generate in a narrow flow channel in an engine room of automobile. Especially CRFM (Condenser-Radiator Fan Module) of MHI is proud on its compact body, so noise control method to predict or prevent BPF noise is very important in this compact module. In this paper, we show the noise prediction technique for a radiator fan of CRFM using unsteady CFD result and assessment result compared with an experimental data.
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Masahiro WATANABE, Kouhei MIZUGUCHI
Article type: Article
Session ID: 1543
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper deals with an experimental study of vortex-induced vibrations of bellows structure subjected to fluid flow. The characteristics of the vortex-induced vibrations and Strouhal number S,p are examined experimentally with changing the pitch length and number of flexible convolutions. The fluid flow around the vibrating convolutions is visualized and the structure of the vortex street is clarified. As a result, it is found that the lock-in phenomenon occurs to the bellows structure in out-of-phase mode due to the coupling between the vibration of the convolutions and vortex street generated along the convolutions.
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Johji SHIMANE, Susumu KUDO, Toshiyuki HAYASE, Ryuhei YAMAGUCHI
Article type: Article
Session ID: 1544
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The flow structure in the right-angle branch has been experimentally studied in laminar steady flow with laser Doppler anemometry and particle image velocimetry. In the previous study, it was clarified that the velocity periodically oscillates in the side branch, and the Strouhal number is independent of cross-sectional area ratio, the flow division ratio of main branch-to-side branch, and the Reynolds number. The mechanism has not clarified adequately. There is another possibility that high shear rate is one of the factors inducing the periodical oscillation in side branch from a result of the velocity oscillation along the separation shearing layer from the entrance of side branch.
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Akira TSURUMAKI, Koji MIYAJI
Article type: Article
Session ID: 1545
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The avoidance of the wing flutter is very important for the safety of the aircraft. Prediction of this phenomenon by CFD improves the efficiency of the design for the aircraft. In this study, numerical method to predict the two-dimension flutter problem is developed. Robust grid deformation method is developed and applied to the three-degree-of freedom flutter. The results successfully captured the flutter boundaries which divides the stable and unstable flight regimes. In addition the effect of the control surface for the wing flutter is shown.
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Keiko ANAMI, Noriaki ISHII, Tatsuya OKU, Yasuhiro TAKATOMI, Takesi OHH ...
Article type: Article
Session ID: 1546
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This study presents a semi-empirical evaluation procedure for determining the hydrodynamic push-and-draw pressure induced by an inclined circular-arc skinplate undergoing streamwise rotational vibration while positioned above a curved dam crest. First, model experiments were conducted to measure the hydrodynamic pressure acting on the rotationally vibrating inclined circular-arc skinplate above the curved dam crest. Then, the resulting experimental values were carefully compared with the calculated hydrodynamic pressure for a vertical flat weir plate above a flat channel floor. It is then shown that the hydrodynamlc pressure on a circular-arc skiplate above a curved dam crest can be evaluated by empiricaily adjusting the pressure correction factor and the gate submergence to reservoir depth ratio in the previously developed calculation procedure for the hydrodynamic pressure induced by a vertical flat weir plate above a flat channel floor.
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Hideyuki Morita, Tomomichi Nakamura, Toshio Ichikawa, Kazuo Hirota, Hi ...
Article type: Article
Session ID: 1547
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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A Neutron Reflector (NR) is a new structure designed for improving the structure reliability of Advanced Pressurized Water Reactors (APWR). The NR is placed in a narrow gap between the NR and a Core Barrel. In the case of a structure surrounded by liquid in a narrow gap, the added fluid mass and the damping increases compared with in the air. This effect is famous for Fluid-Structure Interaction effect (FSI effect) in the narrow gap and it depends on the vibration displacement of the structure. In this paper, results of a model test are shown comparing the data with the calculated ones based on the new analysis method, which is based on a narrow passage flow theory (Morita et al., 2001) combined with the ANSYS computer code. As a result, a new seismic analysis method using the above theory was developed. The analytical results are in good agreement with the test results.
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Ryo MORITA, Fumio INADA, Michitsugu MORI, Kenichi TEZUKA, Yohinobu TSU ...
Article type: Article
Session ID: 1548
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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A steam control valve causes vibration of the piping when the opening is in the middle condition. For the rationalization of maintenance and management in the plant, the cause of vibration should be clarified and the valve should be improved. In current research, we found a valve-attached flow occurs and causes a quasi-periodic spike-type pressure fluctuation at only the middle opening condition in rigid support condition. As this fluctuation causes cyclic side load on the valve body, it is thought to be the cause of vibration. But we don't know the effects of flow-induced vibration when this pressure fluctuation interacts valve vibration because this phenomenon has complex flow structure and the flow is supersonic. This report describes the effect of flow-induced vibration to the flow around the valve. We conducted some experiments with an elastic support, and followings are found. In specific lift range, a resonance between valve and rock-in phenomenon, which the quasi-periodic pressure fluctuation is drawn in a natural frequency of the valve and becomes periodic, occurs. In addition, a damping ratio of the valve decreases and the amplitude has grown in the range.
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Eitaro KOYABU, Tetsuhiro TSUKIJI, Yoshihito MATSUMURA, Taizo SATO
Article type: Article
Session ID: 1549
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In the present study the simplified test model of the commercial reciprocating compressor for an automotive air-conditioner is used to measure the displacement of the suction valves using a strain gauge and to investigate the velocity distributions of the discharge flow from the valves using PIV(Particle Image Velocimetry) technique. The new suction valves with the shape improved from the conventional valve are developed and the results of the measurement of the valve displacement for the new valves are compared with those of the conventional valve. It is found that the vibration for one of the new valves can be suppressed extremely compared with the conventional one from the experiment using both the present test model and the commercial reciprocating compressor. The reason of the vibration-reduction for the new suction valve is discussed from the results of the measurement of the displacement of the valve and the flow analysis. The design guide of the suction valve to prevent the vibration is presented in the study.
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