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Published: September 04, 2010
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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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A1-A8
Published: September 04, 2010
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Keni-ichi FUNAZAKI, Takehiro SHIBA, Kazuki OKAMURA, Masaaki HAMABE
Article type: Article
Session ID: J0501-1-1
Published: September 04, 2010
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This paper deals with studies on the flow field around three types of linear cascades of low pressure turbine (LPT) airfoils with different chordwise loading distributions, while keeping the aerodynamic loading index almost the same. Cylindrical bars on the timing belts work as wake generator to emulate upstream stator wakes that impact the boundary layer on the airfoil suction surface. Hot-wire probe measurement is conducted over the blade suction surface to understand to what extent and how the interaction of incoming wakes as well as freestream turbulence affect the boundary layer and separation bubble. Computational Fluid Dynamics (CFD) analyses are also applied to the flow fields around the cascades, mainly using Large-Eddy Simulation (LES) with dynamic Smagorinsky subgrid scale model.
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Mamoru KIKUCHI, Ken-ichi FUNAZAKI, Reita CHIDA, Katsumi BUNDO, Masaaki ...
Article type: Article
Session ID: J0501-1-2
Published: September 04, 2010
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This paper presents an experimental study of the unsteady flow mechanisms in a single axial flow turbine stage which is simulated the LP turbine airfoils. The target of this study is to verify the influence of the purge flow from the wheelspace cavity on the flow field in the rotor passage, which leads to changes of the secondary flow behavior in the rotor hub region. To observe the unsteady flow pattern at rotor downstream, detailed 3-D unsteady measurements using a slant-type hot wire probe is performed. The result of the unsteady measurement is observed the secondary flow and the leakage flow in the tip region without the purge flow as well as the steady flow measurement with 5-hole probe.
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Yoshihiro ISHIKAWA, Ken-ichi FUNAZAKI, Kazutoyo YAMADA
Article type: Article
Session ID: J0501-1-3
Published: September 04, 2010
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In this paper, SST turbulence model based Detached-eddy simulation (DES) for a low-pressure turbine is examined. The flow condition is a low Reynolds number condition, 5.7×10^4 and a highly loading. In this flowfield, the roll-up of the separated shear layer above the blade suction surface is observed. Before the roll-up, the shear layer keeps the two-dimensionality. After that, the shear layer breaks down and becomes many small parts. In order to predict such flowfield which contains large separation and reattachment in a low-pressure turbine blade, the detailed comparisons between the experimental data and the simulation results are studied. The experimental data is obtained by our research group. The DES result is also compared with two types of LES calculations. The discussion of this paper focuses the turbulence intensity profile in the boundary layer developed on the blade suction surface.
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Masataka UCHIBORI, Yutaka ODA, Kenichiro TAKEISHI
Article type: Article
Session ID: J0501-1-4
Published: September 04, 2010
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Film coolant on gas turbine's vanes and blades is subject to strong turbulent flows containing secondary flows, such as horseshoe vortex, passage vortex, etc. In general, internal flow passage should be included in the numerical domain to give accurate velocity fields at the film-hole exit, which are mandatory for reasonable prediction of the external coolant flows. But it is unrealistic to apply this technique to the LES of realistic cascade flows with multiple film cooling holes. This paper proposes a film-hole model for LES, which is based on random Fourier modes to imitate instantaneous and statistical turbulent flow properties at the film-hole exit without simultaneous analysis in the internal flow passage. The predicted time-mean film cooling effectiveness is compared with experimental data.
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Yasuhiro SASAO, Shinji Takada, Satoru YAMAMOTO
Article type: Article
Session ID: J0501-1-5
Published: September 04, 2010
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This paper presents a numerical study for unsteady flows in a high-pressure steam turbine with a partial admission stage. Compressible Navier-Stokes equations are solved by the high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme, Roe's approximate Riemann solver, and the LU-SGS scheme. The SST-model is used for evaluating the eddy-viscosity. As numerical examples, unsteady two-dimensional flows in a partial admission stage of steam turbine are calculated. The effect of the nozzle box flange to the lift of rotors is numerically investigated. The performance of several types of partial admission stage is parametrically predicted. The efficiency was improved by the sloping flange.
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Koma SATO, Azuma OKUNO, Takeshi KUDO, Shigeki SENOO
Article type: Article
Session ID: J0501-1-6
Published: September 04, 2010
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The mesh generation method for 2-D turbulence analysis of steam turbine cascade was developed. Conventionally, modification of computational mesh according to the turbine blade shape or the analysis condition has often been needed in order to estimate the performance of the steam turbine blade with high accuracy. In this study, the response surface method with Kriging model is used to determine the parameters for mesh generation. This Kriging model receives the blade shape characteristic parameters and the analysis conditions as the inputs and estimates the parameters for mesh generation. In order to build this Kriging model, a number of typical blade's shape characteristic parameters calculated by the dot sequence data and optimal mesh generation parameters searched by Genetic Algorithm are needed. By this parameter estimation, the meshes of the existing turbine blade which have accuracy as much as the meshes generated by the expert were obtained.
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Takahiro NISHIOKA, Toshio KANNO
Article type: Article
Session ID: J0501-2-1
Published: September 04, 2010
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Numerical and experimental studies were carried out to clarify the mechanism behind the stall inception from the rotating instability in a low-speed axial-flow fan. The rotating instability was experimentally observed near the maximum pressure-rise point at the high stagger-angle setting for the rotor blade. The rotating instability was induced by the interaction between the incoming flow, the reversed tip-leakage flow, and the back flow from the trailing edge. Spillage from the leading edge initiated near the inception point of the rotating instability. Tip-leakage vortex breakdown also occurred at the stall point. However, a three- dimensional separation vortex did not develop at the stall point. The numerical and experimental results suggested that the spillage from the leading edge and the tip-leakage vortex breakdown, which did not induce the three-dimensional separation vortex, influenced the stall inception from the rotating instability.
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Hiroaki KIKUTA, Masato FURUKAWA, Kenichiro IWAKIRI, Satoshi GUNJISHIMA ...
Article type: Article
Session ID: J0501-2-2
Published: September 04, 2010
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The effect of stators on the rotating stall inception in axial flow compressor rotors has not been well focused and therefore it has been investigated in the present works. To make the effect of stators clear, numerical analyses in two conditions were conducted: RSA (Rotor-Stator Analysis) and ROA (Rotor-Only Analysis). For RSA, the calculation domain includes stator upstream and downstream of the rotor. For ROA, the calculation domain has no stator. The rotating stall inception point of RSA shows good agreement with the experiment, however, the one of ROA is higher than the experimental inception point. In this paper, the difference between the flow fields for RSA and ROA is discussed and the effect of stators on the rotating stall inception has been elucidated.
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Kazuhiro IUCHI, Yuki OKABE, Junichiro FUKUTOMI, Toru SHIGEMITSU
Article type: Article
Session ID: J0501-2-3
Published: September 04, 2010
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Small-sized axial fan is used as air cooler for electric equipments. But there is demand for higher power of fan according to the increase of quantity of heat from electric device. Therefore, higher rotational speed design is necessary but it causes the deterioration of efficiency and increases the noise. Then the adoption of contra-rotating rotor for small-sized fan was proposed for the improvement of performance. In the present paper, experiment and numerical flow simulation were conducted to investigate the internal flow of conventional small-sized axial fan and contra-rotating small-sized axial fan. And the relationship between the performance and the internal flow field was clarified with the numerical analysis results at partial flow rate.
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Taku Iwase, Nobuaki Arakane, Tetsushi Kishitani, Ryoji Sato
Article type: Article
Session ID: J0501-2-4
Published: September 04, 2010
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Flow fields in half ducted propeller fans have been investigated by FrontFlow/blue, which was computational fluid dynamics software based on Large Eddy Simulation (LES). Aerodynamic noise was calculated by Curie's equation based on pressure fluctuation calculated by LES. 2-blade and 4-blade propeller fans were intended. Noise level of the 2-blade was smaller than the 4-blade by 5.2dB experimentally. LES was conducted to capture the tip vortex, which was characteristic flow field in half ducted propeller fans. Calculated noise level and pressure fluctuation at a suction surface of the 2-blade were smaller than the 4-blade. Difference of overall noise level was 4.8dB. The difference of calculated noise level 4.8dB showed reasonable agreement with measured noise level 5.2dB. The pressure fluctuation near a tip of a trailing edge in the 4-blade was strong. The pressure fluctuation at the tip was therefore found to have a great influence on the noise level.
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Shigeya NAGASAKA, Yusuke ONISHI, Jiro FUNAKI, Katsuya HIRATA
Article type: Article
Session ID: J0501-2-5
Published: September 04, 2010
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The present study is a fundamental approach to reveal the minute fluctuating pressures on three-dimensional blade surfaces of a various low-speed fans. Because, among the concerning physical quantities, the unsteady pressures on the rotating blades give us useful information for the fan flow and its sound-noise level. The authors correct the centrifugal-force effect, the gravitational-force effect and the other leading-error effects for accurate measurements of the minute pressures using a measuring technology developed by the authors (Hirata et al., 2009). As a result, we show the Reynolds-number effects and the spatial distributions on the blade of both time-mean pressure and pressure-fluctuation intensity.
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Takuji HOSOTANI, Rei NAKAMURA, Kenji ONISHI, Junichiro FUKUTOMI, Toru ...
Article type: Article
Session ID: J0501-2-6
Published: September 04, 2010
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Cross-Flow Fan can discharge large flow rate by axially extending it even if it is small. And total pressure coefficient is high, because the flow passes the impeller twice. Therefore, it is has been widely used by the air conditioning machine and cooling fan, etc. However, the performance decrease of Cross-Flow Fan by the scale effect is higher than other fans. In this study, the influence of the miniaturization that appears to the performance of Cross-Flow Fan is examined from the result of the performance test and the CFD analysis.
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Takeshi Honda, Hirotoshi Sato, haruhiko Adachi
Article type: Article
Session ID: J0501-3-1
Published: September 04, 2010
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We computationally and experimentally investigated the effect of tip vortex on the aerodynamic performance of the thin centrifugal blower with the shrouded impeller. The computational results suggested that the tip vortex from the leading edge generated the total pressure loss in the blade passage and that the loss was decreased as the length of unshrouded blade was decreased. The 3D impeller with the short unshrouded blade furthermore reduced the loss in the impeller. The experimental results also suggested that the centrifugal blower equipped the developed 3D impeller provided higher efficiency and low noise.
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Kazutoyo YAMADA, Yusuke TAMAGAWA, Hisataka FUKUSHIMA, Masato FURUKAWA, ...
Article type: Article
Session ID: J0501-3-2
Published: September 04, 2010
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The objective of this study is to investigate the effect of blade count on aerodynamic characteristics of centrifugal compressor impellers with splitter blades. RANS (Reynolds-Averaged Navier-Stokes) simulations were carried out to compare the tip clearance flow field between two compressors. In the tip clearance flow field, the low velocity region, which is generated along the tip leakage vortex, expands as decreasing the flow rate. The difference in the solidity changes the stall onset point, at which the low velocity region in the tip clearance flow interacts with the leading edge of the adjacent blade and the tip clearance flow almost spills ahead of it. In the compressor with low solidity impeller, vortex breakdown happens in the tip leakage vortex because of larger blade loading, which expands the low velocity region and then leads to stall.
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Kazuya MIGITA, Hoshio TSUJITA
Article type: Article
Session ID: J0501-3-3
Published: September 04, 2010
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In the passage of a centrifugal impeller, the passage vortex generates the major part of the secondary flow loss. The passage vortex in a centrifugal impeller is generated by the centrifugal force caused by the curvature of impeller passage and the Coriolis force induced by the rotation. The cross-sectional aspect ratio of the impeller passage varies in the main flow direction. The purpose of this study is to reveal the effects of the cross-sectional aspect ratio on the secondary flow structure and the associated loss generation in the impeller passage by using rotating curved ducts.
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Hisashi Watanabe, Yousuke Sei, Takeshi Yamaguchi, Kaname Matsuyama, To ...
Article type: Article
Session ID: J0501-3-4
Published: September 04, 2010
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Various fluid phenomena appear in AT(automatic transmission) depend on the parts and conditions. New method, cooled by ATF flow, is of advantage for load up AT in the near future. Visualized oil pan model apparatus was established. EFD techniques, using laser sheet visualization, PFV, LDV and thermo couples(TC), evaluate the precision criteria of thermal fluid phenomena analysis. As a result, the velocity accuracy was within 10% and the temperature accuracy was within 15%.
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Masafumi KAWAI
Article type: Article
Session ID: J0501-3-5
Published: September 04, 2010
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The aerodynamic design and validation procedure of an open-type engine run-up facility (RUF) has been developed. Aerodynamic design of RUF has been performed by wind tunnel experiment and CFD. Then, the aerodynamic characteristics of an actual large-scale RUF, constructed based on the new design procedure, was measured. The obtained flow field showed good agreement with CFD results, and the effectiveness of the design procedure based on CFD and wind tunnel experiment has been confirmed. The engine operations were satisfactory under various wind conditions. Furthermore, the data under commercial operations thereafter were collected and analyzed. As the result, the aerodynamic design procedure has been successfully validated.
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Takao Suzuki, Ji Hui, Fujio Yamamoto
Article type: Article
Session ID: J0501-3-6
Published: September 04, 2010
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We acquire particle velocities on a laser-light sheet with PTV and generate time-resolved velocity fields compatible with DNS by rectifying PTV velocity fields to satisfy the continuity. By synchronizing the DNS time step with the PTV frame rate, we feed a rearranged velocity field at each time step and compute the two-dimensional incompressible Navier-Stokes equations over time. At each time step, velocity components are given by the linear combination between those from PTV and those updated with DNS, and their weight is determined so that the hybrid velocity field is directed toward the measured one with a minimum noise level. Thus, unsteady velocity and pressure fields satisfying the governing equations can be simultaneously obtained with the resolution comparable to the numerical simulation. The algorithm and features of this hybrid algorithm are introduced by taking examples from flows past a NACA0012 airfoil and a planar jet.
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Hideaki NANRI, Naoki TANI, Hiroki KANNAN, Yoshiki YOSHIDA
Article type: Article
Session ID: J0501-4-1
Published: September 04, 2010
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This paper reports the effect of the frequency response characteristics of cavitation on cavitation surge using a one-dimensional analytical model applying the acoustic effect of the inlet pipe. The response of cavitation compliance is found to strongly affect the instability of cavitation surge, even though that of the mass flow gain factor does not so. Consequently, as the decrease of the cavitation number, the frequency response of cavitation compliance is vaired, then the cavitation surge with higher frequency becomes stabler and that with lower freqency becomes unstabler.
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Kengo KIKUTA, Satoshi WATANABE, Yoshiki YOSHIDA
Article type: Article
Session ID: J0501-4-2
Published: September 04, 2010
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The degree of thennodynamic effect on inducer cavitation was discussed based on non-dimensional thennodynamic parameter Σ^*= Σ√<C/U^3>. We attempted to relate the descent of cavitation number Δ σ to the thermodynamic parameter Σ^* through the previous experiments. It was found that the depression of cavitation number increases as increasing the thennodynamic parameter Σ^*. However, the effect of nonlinearity of the real vapor pressure (p_v)/temperature (T) curve should be considered to evaluate the thennodynamic effect especially in the case of higher temperature and velocity.
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Shinpei MOMOSAKI, Satoshi WATANABE, Satoshi USAMI, Akinori FURUKAWA
Article type: Article
Session ID: J0501-4-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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An application of contra-rotating rotors, in which a rear rotor is employed in tandem with a front one and these rotors rotate in the opposite direction each other, has been proposed against a demand for developing higher specific speed axial flow pump. It has been found by our previous studies that the rear rotor designed by a conventional axial flow rotor design tended to fail in satisfying the design head. In the present study, an unsteady numerical simulation of internal flow of whole front and rear rotors was carried out to find out a reason for it.
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Taichi TABATA, Masaaki HORIE
Article type: Article
Session ID: J0501-4-4
Published: September 04, 2010
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The magnetically suspended centrifugal blood pump hardly generates hemolysis and thrombus by the levitated rotating impeller in the casing. This pump had been developed for adult patients, but it had never been developed that is suitable for pediatric patients. We examine the hydraulic properties and the pump efficiency of pediatric pump, which is downsized model with same structure of the magnetically suspend system, by using numerical analysis. As a result, it was found that pediatric pump is satisfied for pediatric use and pump performance is improved by using optimum volute geometry.
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Hiroyuki MATSUMIYA, Yuki FUKUI, Masaaki HORIE, Yoshifumi OGAMI
Article type: Article
Session ID: J0501-4-5
Published: September 04, 2010
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The magnetically suspended centrifugal blood pump is one of the highly dependable pumps without thrombus formation and hemolysis for long-term use. This pump has the double volute casing and the impeller of 50mm in diameter with seven right angle blades for levitational stability. It is necessary to downsize the artificial heart to improve the patient's QOL. In this study, computational fluid dynamics analysis was performed about the calculation model with double and single volute and impellers of different diameter for downsizing. As a result, the pump efficiency of the calculation model with single volute casing and small-diameter impeller was found to be improved, and the specific speed of this centrifugal blood pump was found to have an upper bound.
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Shinji OKAMOTO, Junichiro FUKUTOMI, Toru SHIGEMITSU
Article type: Article
Session ID: J0501-4-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The fluid equipment for food has been used in wide-ranging like transportation, the filling, and the quality improvement, etc. As for the research on them, because the targeted fluid is different from air and water, the flowfield is very complex and unclarification. Therefore, the design based on an internal flow is not so performed at present, and it chiefly pays attention to the transit performance and the product development is done. This research targets the food transportation pump. It aims at the improvement of the transit performance considering the quality retention of the food fluid. A centrifugal pump that had four radial blades was designed and produced for this research. A performance and an internal flow when the kinematic viscosity was changed were investigated by the CFD analysis and the experiment. In addition, the design method based on the internal flow is considered.
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Hiroyuki HIRAHARA, Yuya TOSHIMA, Hirofumi KADONO, Violeta MADJAROVA
Article type: Article
Session ID: J0503-1-1
Published: September 04, 2010
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In the present paper, a development for two-dimensional pressure measurement was reported. The technique is based on a digital speckle pattern interferometry with a visco-elastic gel pressure sensor, which was developed in our group recently. The surface displacement due to the pressure change was measured with DSPI. The temporal signal intensity was analyzed with Hilbert transformation method. An inclined impinging jet was measured as a sample case. The obtained distribution shows a fair agreement with that by CFD.
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Shinya YAMANADA, Shigeru MURATA, Syunsuke KOKAJI, Yohsuke TANAKA
Article type: Article
Session ID: J0503-1-2
Published: September 04, 2010
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This paper presents a numerical evaluation system of noninvasive evaluation of fractured bone based on speckle interferometry. The system simulates the deformation of an object using a particle method. Out-of-plane vibration of the object surface is obtained as numerically speckle fringes generated by a speckle interferometry based on wave optics. In the present numerical simulation, the velocity of impact object and the thickness of the external layers of three-layer object are employed as simulation parameters, and their influence on the evaluation index of internal state is examined by using the proposed numerical evaluation system. The relation between experimental parameters and the evaluation index is shown and the usefulness of the proposal system is shown.
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Yohsuke TANAKA, Shigeru MURATA
Article type: Article
Session ID: J0503-1-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The present study shows the observation of a buckling column by using digital holographic Particle-Tracking Velocimetry (PTV). The column is made of acrylic resin and tracer particles are uniformly dispersed in the column. The displacement of the column is obtained by each dispersed particle's positions between unloaded and loaded beam. Three-dimensional deflection of the particle is measured by digital holographic PTV. The column is installed in the water tank which is filled with a refractive-index matching liquid. Aqueous solution of Sodium iodide is used as a matching liquid. Experimental results on the three-dimensional deflection field and the comparison of present method and CAE analysis are presented.
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Motoharu FUJIGAKI, Akihiro MASAYA, Yoshiharu MORIMOTO, Ryosuke MURAKAM ...
Article type: Article
Session ID: J0503-1-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In this paper, an accuracy estimation method of 3D-shape measurement using whole-space tabulation method (WSTM) is proposed. WSTM is a calibration method for a shape measurement. Pixel-by-pixel calibration tables are produced with multiple reference planes. This method excludes a lens distortion and the intensity warping of the projected grating in measurement results theoretically. A high-speed and accurate shape measurement system can be possible to develop easily using this method. Random noise, however, causes error in this method. The primary factor of error is random noise occurring in an imaging device. The accuracy of a shape measurement setup can be estimated from the random noise occurring in the imaging device.
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Hiroki SAKAMOTO, Sigeo HOSOKAWA, Akio TOMIYAMA
Article type: Article
Session ID: J0503-2-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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High spatial and temporal resolutions are required in velocity measurements for turbulent flows to examine turbulence characteristics accurately. In this study, we proposed a spatial filter velocimetry (SFV) based on a frequency analysis of time-series spatially-filtered particle images. Since this method can measure velocity from one particle in a measurement region, it enables us to measure the velocity with high spatial and temporal resolutions. We developed a SFV system and applied it to laminar and turbulent flows in a duct to examine its feasibility. Through comparisons between the velocities measured by SFV and LDV, we confirmed that SFV accurately measures the mean velocity and turbulent intensity with spatial and temporal resolutions as high as LDV.
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Kodai HANYU, Takayuki SAITO
Article type: Article
Session ID: J0503-2-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Acid rain is one of the serious problems for the global environment. It causes harms to the earth such as the lake acidification, melting of metallic constructions and so on. For mitigating these harms, we need to understand the generation mechanism of acid rain. For realizing it, we have newly developed a photoelectric optical fiber probe to measure pH, velocity and diameter of acid rain simultaneously. This probe has two functions of measuring the concentration of droplet by an electric sensor and measuring the velocity and diameter of droplet by an optical sensor. In this research, we examined modeled droplets including CO_2 gas. We describe the reliability of this probe for the droplet measurement of acid rain.
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Tetsuya YANO, Naohiro MARUBAYASHI, Tsukasa HORI, Jiro SENDA, Hajime FU ...
Article type: Article
Session ID: J0503-2-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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For the reduction of diesel engine emissions, it is significant to clarify the spray atomization and formation processes. In this investigation, a detailed observation of fuel droplets characteristic was made by applying a double exposure method using a color film, a light fiber and a wavelength converter to a previous measurement technique. The photographic system is composed of a specialized lens system, and enables to measure the whole spray shape and fuel droplets characteristics at an instant. The light source is the second harmonic, and the third harmonic of Nd:YAG laser. This technique enables the spray measurement of the chronological order. In addition, it is expected new knowledge about a spray atomization mechanism be obtained.
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Takamichi KONO, Shigeru MURATA, Yohsuke TANAKA
Article type: Article
Session ID: J0503-2-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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This paper presents an accurate method for reconstruction of digital holography in 3D space with two different wavelengths. In digital holography, hologram recording and image reconstruction are carried out with single wavelength. However the proposed method records hologram and reconstruct images with two wavelengths. The performance is evaluated in gray level distribution along depth direction in reconstructed images. In numerical simulation, it is found that the accuracy of the proposed method in depth position of target objects is better than that of previous method.
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Tuananh NGUYEN, Mizuyasu KOIDE, Tsutomu TAKAHASHI, Masataka SHIRAKASHI
Article type: Article
Session ID: J0504-1-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Previous experimental work carried out by the present authors showed that two types of longitudinal vortices shed periodically from a cruciform two-identical-circular-cylinder system in uniform flow. The specific aim of this work is to investigate universality of this phenomenon by carrying out experiments for smaller sizes of cylinders in a high-velocity water tunnel. In addition to the velocity, the alternating lift force loading on the stationary upstream cylinder is measured by using a load-cell. Experimental results show that longitudinal vortices also shed periodically from systems with cylinder diameter of 10 and 15 mm in water flow. Relationships of the Strouhal number and the lift force coefficient for the vortex shedding against Reynolds number agree well with the previous data except a peculiar vanishing of Necklace vortex when Re is larger than 20000.
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Keita SAITO, Hajime FUJITA, Yasumasa SUZUKI
Article type: Article
Session ID: J0504-1-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The Aeolian tone generated from two-dimensional objects has been studied widely in the past. In this study, the Aeolian tone and the related flow fields of three types of tapered cylinders are measured and are compared with those of straight cylinders. It is found that the level of the Aeolian tone decreases with the taper ratio. For the cylinder of smaller taper ratio, different peaks in the velocity fluctuation appear at different spanwise locations, corresponding to different peaks in Aeolian tone spectrum. The wake for higher taper ratio cylinder does not show the existence of the Karman vortex shedding and no peaks of the Aeolian tone are found.
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Takashi NISHIHARA, Yuzuru EGUCHI
Article type: Article
Session ID: J0504-1-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Free-vibration tests of a yawed circular cylinder were conducted in a water tunnel at three yaw angles of 0, 30 and 45 degrees to clarify the effects of the yaw angle on the vibration response. As a result, the vortex-induced in-line vibration of a yawed circular cylinder can be avoided at least at intermediate subcritical values of the Reynolds number, by using the criterion that the reduced velocity is less than 1, where the reduced velocity is calculated using the normal component of the incident flow velocity. A small-amplitude transverse vibration can occur at a reduced velocity lower than the onset flow velocity of in-line vibration when the reduced damping is very low.
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Yusuke KAWABATA, Tsutomu TAKAHASHI, Mizuyasu KOIDE, Masataka SHIKARASH ...
Article type: Article
Session ID: J0504-1-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Wind tunnel experiments are carried out to investigate the characteristics of cross flow vibration of a square cylinder with a side length d=26mm induced by setting a plate in the wake of the square cylinder. When a plate of width w=d and cross flow length l_d=2d is set with a gap ratio s/d<1.O, a large vibration occurs at U>5m/s with the maximum amplitude at around s/d=0.3. The amplitude at s/d=0.3 increases divergently with flow velocity. Measurement of the lift force on the square cylinder and the velocity in the near wake for the corresponding fixed system showed no evidence for periodic change of flow responsible for the vibration. These results show that the vibration is caused by the fluid-elastic instability but not by a periodic vortex shedding. Hence, the name "Wake Body Interference Fluid Elastic Vibration (WBIFEV)" for this vibration given in the previous paper is confirmed to be reasonable.
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Tomomichi NAKAMURA, Hironori MAEDA, Tsuyoshi SOMEKAWA, Ryo BABA, Hiroa ...
Article type: Article
Session ID: J0504-1-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The importance of the in-flow oscillation of a single cylinder in cross-flow has been in the spotlight since an accident in a FBR-type reactor. However, in-flow oscillations can also be observed in heat exchanger tube arrays. Previous reports show some interesting phenomena on the oscillation of cylinder arrays. In this paper, detailed observation on the effect of the pitch ratio for pairs of cylinders, in parallel and in tandem, is highlighted in the range of low flow velocities, where each cylinder can move only in a given direction. The motion of the cylinders is measured by attached strain gages and by a high-speed digital video camera.
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Youmin LEE, Hiroshi YOKOYAMA, Chisachi KATO
Article type: Article
Session ID: J0504-1-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Aerodynamic sound has been numerically predicted by two methods. First is DNS which solve the compressible Navier-Stokes equations directly, and Second is analyzing Lighthill Tensor which is the right side of Lighthill's equation. Recently, analyzing Lighthill Tensor is expected heighten because of high cost of DNS. However, this method still has several problems especially about an end of computational domain. To solve computational domain problem, we use DNS in this study. The sound field radiated from the two-dimensional square cylinder in a uniform flow is changed by the number of vortices captured by computation. In order to clarify acoustical vortex, we investigate sound mechanism. In addition, we calculate Powell's and Lighthill's acoustic sound sources.
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Shoji TAKADA, Atsuhiko SHINTANI, Tomohiro ITO
Article type: Article
Session ID: J0504-2-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The structure subjected fluid force in narrow passage is sometimes exposed to unstable vibration. We consider the availability of this fluid force and try to develop the efficient driving mechanism. The driving body in narrow passage is modeled as a link mechanism. Fluid-structure coupled equations are derived based on the equation of continuity and the Navier-Stokes equations. Through these equations, fluid- structure coupled modes in the system are obtained. Considering the mechanism for unstable vibration, efficient driving force is generated from small input torque, which can make efficient driving.
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Tetsuya KURIBAYASHI, Takayoshi ICHIYANAGI, Takao NISHIUMI, Kenta KIKUT ...
Article type: Article
Session ID: J0504-2-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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A multi degree of freedom type Helmholtz resonator was originally devised in order to attenuate the successive several harmonics of the fixed discrete-frequency pressure pulsation such as those generated by a fixed speed hydraulic pump. However, pump rotational speed is often varied in order to fulfill certain operational cycle in some hydraulic actuator application. Therefore, the development of the present resonator applying to a hydraulic system operated under the variable speed condition is a final goal of this research project. In this report, as a first step, a theoretical feasibility study of the present resonator is mainly described.
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Keiko ANAMI, Noriaki ISHII, Takuma TSUJI, Masaru GOTO, Kazuaki YAGI
Article type: Article
Session ID: J0504-2-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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As part of the investigation of the dynamic instability of the gate closely related to the Folsom dam Tainter-gate failure, and in order to assure the dynamic stability of the gate, the field vibration tests on three full-scale operational Tainter-gates were conducted. From these tests, the possible existence of another coupled-mode self-excited vibration mechanism, which involves the dangerous dynamic coupling of the whole gate rigid-body rotational vibration with a "parallel" bending of the skinplate was suggested. This paper presents that the 2-dimensional model test results, which was undertaken to confirm the existence of the coupled-mode self-excited vibration with skinplate parallel bending mode.
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Hiroaki HISADOMI, Hiroshi YAMAGUCHI, Naoyuki MAGARA
Article type: Article
Session ID: J0504-2-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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There is a check valve which is widely used as one of the directional control valve. The valve is simple structures that push the valve body by spring. But, vibration may cause the internal state of flow and channel shape and the valve body. It is important to assess the mechanism of this phenomenon and valves behavior in terms of longevity and reliability of fluid machinery. Therefore, in this research, we reveal the internal flow condition and evaluate the relevance of the valve body vibration by using CFD simulation and visualization system that models the valve.
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Yuta TOMINAGA, Shigehiko KANEKO
Article type: Article
Session ID: J0504-2-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Axial vibration characteristics of centrifugal turbopumps are extremely complex. In the balance piston system, the axial vibration due to flow passing through the balance orifice occurs in some cases. Normally, the swirl flow may suppress the axial self-excited vibrations. But the mechanism is unclear. Therefore, in this study, we manufactured an experimental apparatus including a partial model of the balance piston in the centrifugal turbopump, and the effects of swirl flow on the vibration performance of the balance piston in the centrifugal turbopump are investigated. As a result, it is noted that the peak value on displacement from FFT at 120Hz decreases as the swirl flow increases.
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Shirou TAKAHASHI, Yukihiro SOGA, Toshihiro Ootsuka, Kenichi Kawabe, Ki ...
Article type: Article
Session ID: J0504-3-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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A lot of thermometers are used for monitoring the fluid and reactive conditions in thermal and nuclear power plants. From the experience of failure of the thermometer well due to flow-induced vibration in fast breeder reactor "MONJU" JSME proposed the guideline for the flow-induced vibration of a cylindrical structure. Its applicable scope is limited in structures subjected to homogeneous and cross flow. In some case of monitoring of reaction in pressure vessel, thermometer wells are installed downstream bend pipe and subjected to complicated flow. In the present study, the structural integrity of the thermometer well installed in pressure vessel was evaluated through scale tests with respect to flow-induced vibration. Lock in synchronization would not occur for the thermometer well. The predictable maximum fluctuating stresses induced by the turbulence and the Karman vortex shedding were bellow 1MPa and was satisfied the allowable level of fatigue limit.
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Hideki SHIMOHARA, Katsuya HIRATA, Motoe YASHIMA, Takashi TSUJI
Article type: Article
Session ID: J0504-3-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Tn many fluid-structure interaction problems, the virtual mass, namely, the added mass is one of important interests. In the present study, we investigate the validity of a method previously proposed by the authors in order to specify the added mass coefficients of arbitary two-dimensional bodies efficiently and conveniently. In the new method, we consider a two-dimensional incompressible viscous fluid under the assumption of an infinitesimal oscillation amplitude of the body, and properly modify the Navier-Stokes equations into linear equations, that is , the Brinkman equations. The solving method is based on a discrete singularity method (referred to as DSM). We solve the full Navier-Stokes equations by a finite difference method (referred to as FDM) to specify the valid range of the new method. Comparing such solutions we confirm the valid range for the DSM method.
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