Details of a Researcher - Obi, Shinnosuke

Papers - Obi, Shinnosuke

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Experimental and Computational Study of Rotational Lift Production of Insect Flapping Wing

Applied Sciences 2026.01

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COMPARATIVE STUDY OF MINI PROPELLER GEOMETRY FOR THRUST ENHANCEMENT ON A LABORATORY-SCALED WATERCRAFT USING OPENFOAM

Truong H., Beninati M.L., Obi S., Doan M.

American Society of Mechanical Engineers Fluids Engineering Division Publication Fedsm 1 2025

ISSN 08888116

Propeller geometry significantly influences the performance and efficiency of propulsion systems in watercraft. This study investigates the thrust enhancement potential of mini screw-type propellers on a laboratory-scaled watercraft through computational fluid dynamics (CFD) simulations conducted using OpenFOAM. The unsteady Reynolds-Averaged Navier-Stokes (RANS) equations, coupled with the k-omega-SST turbulence model, are applied to simulate fluid-structure interactions. The sliding mesh technique is utilized to model the rotation of the propellers with high fidelity. The Reynolds number, based on propeller diameter, is approximately 50,000. Seven distinct propeller geometries are analyzed, with variations in the number of blades and helical pitch angles. Performance evaluation focus on thrust force and the presentation of wake flow features for each design. The findings highlight the relationship between propeller geometry and hydrodynamic performance, offering insights into wake structures and flow dynamics. This study provides a systematic approach to propeller design for laboratory-scaled watercraft, contributing to the broader understanding of thrust enhancement and propulsion efficiency in small-scale experimental systems.

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Comparative Analysis of Vortex Field Measurement around MHK Turbine Blades using PIV and CFD Techniques

Hafdaoui A., Tanaka S., Doan M.N., Obi S.

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) 8 2024.11

Research paper (international conference proceedings), Joint Work, Last author, Accepted

Cross-flow turbines have been recently re-discovered in the fields of wind and tidal energy thanks to the high power density they can provide when arranged in arrays. In this paper, we investigate the mechanism of torque generation and maintenance of a pair of miniature Marine Hydrokinetic Turbines via Particle Image Velocimetry, providing new insights on the influence of vortex shedding onto the lift generation process. The velocity field around the blades was measured for two different tip speed ratios and across various configurations of the devices, to then evaluate the forces involved by performing a momentum balance over moving control volumes. Our findings suggest that a lift force was first generated, in line with the airfoil theory, by the flow acceleration on the inner surface of the blade, and was subsequently maintained after the onset of dynamic stall by the low pressure associated with a leading-edge vortex. Furthermore, increases in tip speed ratio and blockage effect were observed to positively impact vortex strength and torque production. The results were compared with two-dimensional CFD studies for the purpose of validating the control volume method for torque estimation, as well as discussing and quantifying the 3D effect.

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Revisiting the Flow Instability of Shrouded Corotating Disk Systems

Watanabe A., Obi S.

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) 5 2024.11

Research paper (international conference proceedings), Joint Work, Corresponding author, Accepted

In disk drive systems, flow-induced vibration, often attributed to turbulent fluid motion, presents a significant challenge due to its wide-ranging frequency spectra. Helium-filled enclosures have been introduced to mitigate this issue by reducing the force exerted by fluid motion, owing to the lower gas density compared to air. This density reduction leads to a decrease in the inertia force relative to the viscous force, lowering the Reynolds number by nearly an order of magnitude and resulting in an anticipated transition from turbulent to laminar flow. However, the transitional regime poses challenges, potentially causing intermittently alternating flow motion between turbulent and laminar states, characterized by velocity fluctuations of larger magnitude. Our experimental study involved a series of tests with a system comprising five 3.5-inch disks enclosed within a cylindrical casing. Varying the disk rotation speed from 600 rpm to 7200 rpm resulted in Reynolds numbers ranging from about 1×104 to 1×105. While air-filled configurations consistently exhibited fully turbulent flow, helium-filled setups demonstrated laminar characteristics at lower Reynolds numbers. Our findings suggest transitional behavior at intermediate Reynolds number ranges, indicating a shift from stable to unstable flow patterns. These observations underscore the potential challenges associated with helium-filled disk systems.

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Numerical Study on the Hydrodynamic Performance of a Flexible Caudal Fin with Different Trailing-Edge Shapes

Khin M.H.W., Obi S.

Biomimetics (MDPI) 9 ( 7 ) 2024.07

Research paper (scientific journal), Joint Work, Last author, Accepted

This paper presents a three-dimensional fluid-structure-coupled simulation of a flexible caudal fin with different trailing-edge shapes. The influences of caudal-fin shape on hydrodynamic performance are investigated by comparing the results of a simplified model of a square caudal fin with forked and deeply forked caudal fins under a wider range of non-dimensional flapping frequency, 0.6 < f* < 1.5, where f* is the ratio of flapping frequency to the natural frequency of each caudal fin, i.e., f* = f/fn. The leading edge of each caudal fin is forced to oscillate vertically in a water tank with zero free-stream conditions. The numerical results show that the amount of forking in the geometry of the caudal fin has significant effects on its hydrodynamic performance. A comparison of thrust coefficients shows that the square caudal fin has a greater thrust coefficient in the non-dimensional frequency range of 0.6 < f* < 1.2, while the deeply forked caudal fin generates higher thrust when 1.2 < f* < 1.5. In terms of propulsive efficiency, the square caudal fin is more efficient when 0.6 < f* < 0.9, while the propulsive efficiency of a deeply forked caudal fin is significantly enhanced when 0.9 < f* < 1.5. Based on our results, the deeply forked caudal fin has greater thrust coefficients and a higher propulsive efficiency in a higher frequency range than the natural frequency of each caudal fin. The thrust characteristics and flow fields around each caudal fin are investigated in detail.

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Experimental Study of Instantaneous Velocity-Pressure Correlations by PIV Measurement in a Turbulent Pipe Flow with Drag Reduction by Added Surfactant

Yoshida, T., Obi, S.

13th International Symposium on Turbulence and Shear Flow Phenomena 2024.06

Research paper (international conference proceedings), Joint Work, Last author, Accepted

Three-Dimensional Hydrodynamic Analysis of a Flexible Caudal Fin

May Hlaing Win Khin,Shinnosuke Obi

Applied Sciences (MDPI) 12 ( 24 ) 2022.12

Research paper (scientific journal), Joint Work, Last author, Accepted

A 3D fluid–structure coupled simulation of a square flexible flapper, the basic model of a caudal fin, is performed to visualize the flow field around the caudal fin. A plate immersed in a water tank is driven to oscillate vertically by its leading edge. A quantitative analysis of the thrust generated by the plate, which is difficult to explore experimentally, is performed over a range of non-dimensional flapping frequencies 0.93 (Formula presented.) 1.47 to explore the mechanism of thrust generation in more detail. Comparisons are made between three different flapping frequencies around the structural resonance. Numerical results at different flapping frequencies provide a reasonable estimate of the trailing edge amplitude and phase lag of the motion of the plate’s leading and trailing edges. The pressure distribution and deformation of the plate are analyzed to estimate the time evolution of the maximum and minimum thrust generation during the flapping period. Variations in pressure distribution on the plate surface are mainly due to the displacement of the trailing edge relative to the leading edge. Thrust is mainly provided by the pressure difference at the trailing edge. The maximum thrust was found to correspond to the maximum relative deformation of the trailing edge. The optimum frequency (Formula presented.) = 1.2 corresponding to the maximum thrust generation does not coincide with the structural resonance frequency, but remains at a frequency slightly higher than the resonance. These results indicate that the relative deformation of the plate plays an important role in the estimation of the flow field and the associated thrust generation. The numerical results may provide new guidelines for the design of robotic underwater vehicles.

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Fluid Flow Induced By An Elastic Plate In Heaving Motion

May Hlaing Win Khin, Kentaro Kato, Hyung Jin Sung, Shinnosuke Obi

ASEAN Engineering Journal (Universiti Teknologi Malaysia) 12 ( 3 ) 1 - 9 2022.08

Research paper (scientific journal), Joint Work, Last author, Accepted

We perform three-dimensional simulations of an elastic plate heaving in a sinusoidal motion with different frequencies to explore the effects of the forcing heaving frequency on the hydrodynamic force generation and flow structures. It is aimed to simulate the motion of a rectangular elastic plate, representing a simplified flexible wing or fin, placed in an open water tank as in a corresponding experimental study. The top edge of the plate oscillates sinusoidally in water at rest. Simulations are conducted for the fluid structure interaction of an elastic plate with a special version of the open-source library C++ OpenFOAM, foam-extend-3.2. The plate oscillates at different heaving frequencies in a range of 3.5 Hz and 4.5 Hz. Experiments are carried out to validate our simulations. The results are in a good agreement with the experiment in terms of the representation of the resonant frequency and the induced hydrodynamic forces. It is found that the hydrodynamic force and propulsive efficiency are mainly affected by the elastic deformation and forcing heaving frequencies. The generated thrust is observed to be significantly enhanced at the resonant frequency, while the propulsive efficiency is increased at the heaving frequency which is greater than the resonant frequency. The results of our simulations point to the importance of resonant flapping frequency for considering the optimal heaving frequency to achieve the best performance and to get the improved thrust force, which are crucial for the locomotion of birds, insects, fishes, flapping-based micro air and underwater vehicles.

Keywords: Flexible wing, fluid structure interaction, resonant frequency, thrust force, underwater vehicles

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Numerical study of the dynamic stall effect on a pair of cross-flow hydrokinetic turbines and associated torque enhancement due to flow blockage

Doan M.N., Obi S.

Journal of Marine Science and Engineering (Journal of Marine Science and Engineering) 9 ( 8 ) 2021.08

Research paper (scientific journal), Last author, Accepted

An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and applied for a laboratory-scaled cross-flow hydrokinetic turbine and a twin turbine system in counter-rotating configurations. The computational fluid dynamics (CFD) model was compared with previously published experimental results and then used to study the turbine power output and relevant flow fields at four blockage ratios. The dynamic stall effect and related leading edge vortex (LEV) structures were observed, discussed, and correlated with the power output. The results provided insights into the blockage effect from a different perspective: The physics behind the production and maintenance of lift on the turbine blade at different blockage ratios. The model was then applied to counter-rotating configurations of the turbines and similar analyses of the torque production and maintenance were conducted. Depending on the direction of movement of the other turbine, the blade of interest could either produce higher torque or create more energy loss. For both of the scenarios where a blade interacted with the channel wall or another blade, the key behind torque enhancement was forcing the flow through its suction side and manipulating the LEV.

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Flow field measurement of laboratory-scaled cross-flow hydrokinetic turbines: Part ii—the near-wake of twin turbines in counter-rotating configurations

Doan M.N., Kawata T., Obi S.

Journal of Marine Science and Engineering (Journal of Marine Science and Engineering) 9 ( 7 ) 2021.07

Research paper (scientific journal), Accepted

Cross-flow hydrokinetic turbines have sparked interest among fluid dynamicists for their potential for power enhancement in paired configuration. Following the first part of a laboratory-scaled turbine wake measurement project, this second part presents a monoscopic particle image velocimetry measurement of the near-wake of two cross-flow hydrokinetic turbines in six different counter-rotating configurations. The turbines operated in a small water flume at an average diameter-based Reynolds number of 2 × 104 with the incoming streamwise velocity of 0.316 m/s. The six configurations included two turbine separation distances, two turbine phase angles differences, and two different relative incoming flow angles. Similar to the observation of the single turbine configurations in part I, a correlation between flow field structures and the corresponding power output was observed. Effects of each parameter of the counter-rotating configurations are further discussed, which suggest guidelines for setting up multiple devices in a power farm. This article is accompanied by all full numeric data sets and videos of the results.

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Observation and discussion of leading edge vortex shedding from laboratory-scaled cross-flow hydrokinetic turbines in counter-rotating configurations

Doan M., Kai Y., Kawata T., Alayeto I., Obi S.

American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM (American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM) 3 2021.07

ISSN 08888116

In 2011, John Dabiri proposed the use of counter-rotating vertical-axis wind turbines to achieve enhanced power output per unit area of a wind farm. Since then, various studies in the wind energy and marine hydrokinetic (MHK) literature have been dedicated to pairs of vertical axis turbines in both co-rotating and counter-rotating configurations, in terms of their power production, wake characterization, and optimal array design. Previous experimental works suggest an enhancement of up to 27.9% in the system power coefficient of pair configurations compared to a single turbine. Additionally, previous numerical studies have indicated that the increased power output is correlated with higher torque on the turbine blades which correspondingly produces a stronger leading edge vortex. This paper presents an extended investigation into a pair of laboratory scaled cross-flow hydrokinetic turbines in counter-rotating configurations. Experiments were conducted to observe, compare, and discuss the leading edge vortex shedding from the turbine blades during their positive torque phase. The turbines operated in a small water flume at the diameter-based Reynolds number of 22,000 with a 0.316 m/s freestream velocity and 4% turbulent intensity. Using a monoscopic particle image velocimetry setup, multiple realizations of the water flow around each blade at their positive torque phase were recorded and phase-averaged. Results show consistent leading vortex shedding at these turbine angles while a correlation between the turbine power performance and the vortex size and strength was observed.

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Flow field measurement of laboratory-scaled cross-flow hydrokinetic turbines: Part i—the near-wake of a single turbine

Doan M.N., Kai Y., Kawata T., Obi S.

Journal of Marine Science and Engineering (Journal of Marine Science and Engineering) 9 ( 5 ) 2021.05

Research paper (scientific journal), Joint Work, Corresponding author, Accepted

Recent developments in marine hydrokinetic (MHK) technology have put the cross-flow (often vertical-axis) turbines at the forefront. MHK devices offer alternative solutions for clean marine energy generation as a replacement for traditional hydraulic turbines such as the Francis, Kaplan, and Pelton. Following previous power measurements of laboratory-scaled cross-flow hydrokinetic turbines in different configurations, this article presents studies of the water flow field immediately behind the turbines. Two independent turbines, which operated at an average diameter-based Reynolds number of approximately 0.2 X 105, were driven by a stepper motor at various speeds in a closed circuit water tunnel with a constant freestream velocity of 0.316 m/s. The wakes produced by the three NACA0012 blades of each turbine were recorded with a monoscopic particle image velocimetry technique and analyzed. The flow structures with velocity, vorticity, and kinetic energy fields were correlated with the turbine power production and are discussed herein. Each flow field was decomposed into the time averaged, periodic, and random components for all the cases. The results indicate the key to refining the existed turbine design for enhancement of its power production and serve as a baseline for future comparison with twin turbines in counter-rotating configurations.

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Twin marine hydrokinetic cross-flow turbines in counter rotating configurations: A laboratory-scaled apparatus for power measurement

Doan M.N., Kai Y., Obi S.

Journal of Marine Science and Engineering (Journal of Marine Science and Engineering) 8 ( 11 ) 1 - 16 2020.11

Research paper (scientific journal), Joint Work, Last author, Accepted

This article proposes an experimental apparatus design to measure the power of a cross-flow marine hydrokinetic turbine system operating in a laboratory water tunnel. Data, from one Hall sensor output signal, was processed to capture the three types of torque exerted on the turbines: mechanical loss, brake, and hydrodynamic torque. The method was then applied to compare the power of a twin turbine system in different counter-rotating configurations. Controlled by a hysteresis brake, the tip-speed-ratio was varied in a constant freestream velocity of 0.316 m/s. While the braking torque was independent of the speed, the mechanical loss was found to depend on the system rotational speed and the amount of mass mounted on the mechanical support. In a counter-rotating configuration, the turbines were synchronized through a pair of spur gears and timing pulleys. Operating at the average chord based Reynolds number of 8000, each turbine had three NACA0012 blades mounted at 15 pitch angle. The power coefficient results of 8 turbine configurations showed the tendency of power enhancement of counter-rotating configurations due to blade interaction and increase in blockage ratio. Comparison of the results suggested direct application in a river flow scenario and manipulation of the blade interaction for optimal power production. ◦

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円管中に設置された半円オリフィス後流における界面活性剤水溶液流れのステレオ PIV 計測

河合正郎，河田卓也，小尾晋之介

流体工学部門講演会講演論文集, OS01-02 2020

円筒容器内で回転する積層円盤間での遷移レイノルズ数領域における流体関連振動に関する実験的研究

服部能幸，河田卓也，小尾晋之介

流体工学部門講演会講演論文集, OS13-01 2020

Wake characteristics comparison between isolated and pair configurations of marine hydrokinetic crossflow turbines at low Reynolds numbers

Alayeto I.H., Doan M.N., Kumazawa K., Obi S.

ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019 (ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019) 1 2019

ISSN 9780791859025

Wake characteristics and power coefficient of laboratory scaled marine hydrokinetic cross flow turbines were studied both experimentally and numerically. Single and turbine pair configurations were experimentally tested in a 3.5 m long, 0.3 m wide and 0.15 m deep water channel facility. Each turbine was built with three straight NACA0012 blades with chord 2.54 cm and 6.828 cm diameter, corresponding to a solidity of 1.2. The Reynolds number associated with the velocity given by the water pump and blade chord oscillated near 7000. Empirical power measurement was obtained multiplying the average torque by average rotational velocity. These measurements were obtained with a magnetic hysteresis brake utilized as control system and a Hall effect sensor used as speed transducer, respectively. Wake velocity profile was obtained by image processing of Particle Image Velocimetry (PIV) measurements at different positions. The empirical results were contrasted with numerical computational fluid dynamics (CFD) simulations carried out with Salome and OpenFoam. The computational model solved the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations in 2 dimensions using the turbulence models k-? Shear Stress Transport (SST) and Spallart-Allmaras (SA). The experimental and numerical results show a clear difference of power coefficient and wake shape for both turbine configurations. This influence of two nearby blades on the flow can be exploited to obtain higher ratios of power per land area, leading to an increase of the overall generation of a power plant by a careful arrangement.

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Computational fluid dynamic analysis of a marine hydrokinetic crossflow turbine in low Reynolds number flow

Doan M.N., Alayeto I.H., Kumazawa K., Obi S.

ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019 (ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019) 2 2019

ISSN 9780791859032

This study focuses on surveying different turbulence models and dynamic mesh techniques to simulate a marine hydrokinetic (MHK) crossflow turbine at Re ˜ 7,000. While several research projects have shown that studies of MHK devices in low Re flow could still yield interesting and significant results, existing computational fluid dynamic (CFD) simulations were conducted at the chord based Re of 10 ~ 10 . The wake and power production of a laboratory-scaled MHK crossflow turbine were numerically simulated and compared with relevant experimental data. The vertical axis turbine operated in a small flume with 20% blockage ratio and was fabricated by mounting three NACA0012 (2.54 cm chord length) straight blades at a radius of 3.41 cm and 15 pitch angle. Within OpenFOAM environment, blade-resolved models were built with Spalart-Allmaras, k-omega shear stress transport (SST), and k-kl-omega unsteady Reynolds-averaged Navier-Stokes simulation (URANS) in both two and three dimensions. Results from each model were compared with the experimental power measurement and flow field obtained by monoscopic particle image velocimetry (2D PIV). Additionally, four different techniques for moving the solid boundaries (turbine blades) in the unsteady simulation were presented and compared in terms of solution consistency and required computational power. Overset mesh, time-deforming mesh, and moving immersed boundary are all available in this open source environment, beside the common rotating mesh technique, and possess the potential to be applied to a more complicated configuration of turbines. c 5 6 ?

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Experimental study on modeled caudal fins propelling by elastic deformation

Baba N., Obi S.

American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM (American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM) 1 2018

ISSN 9780791851555

Copyright © 2018 ASME. The present study proposes a new device for the experiment of self-propelling bodies in the water. As opposed to the studies in the past whose experiments were often carried out in a water channel with a given freestream velocity, the new device allows the model to swim under an actual self-propelling condition. The adopted model mimics the caudal fin of various shapes and made of elastic material, and the self-propelling speed is investigated primarily as a function of the forcing frequency. The influence of the amplitude of forced vibration and the materials of different elasticity is also investigated. The flow field around the model fin has been measured by PIV to characterize the flow pattern produced by the fin-motion.

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Experimental and computational fluid dynamic analysis of laboratory-scaled counter-rotating cross-flow turbines in marine environment

Doan M., Alayeto I., Padricelli C., Obi S., Totsuka Y.

American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM (American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM) 2 2018

ISSN 9780791851562

Copyright © 2018 ASME Power generation of laboratory-scaled marine hydrokinetic (MHK) cross-flow (vertical axis) turbines in counter-rotating configurations was scrutinized both experimentally and numerically. A tabletop experiment, designed around a magnetic hysteresis brake as the speed controller and a Hall-effect sensor as the speed transducer was built to measure the rotor rotational speed and the hydrodynamic torque generated by the turbine blades. A couple of counter-rotating straight-three-bladed vertical-axis turbines were linked through a transmission of spur gears and timing pulleys/belt and coupled to the electronic instrumentation via flexible shaft couplers. A total of 6 experiments in 3 configurations, with various relative distances and phase angles, were conducted in the water channel facility (3.5 m long, 0.30 m wide, and 0.15 m deep) at rotor diameter base Reynolds number of 20,000. The power curve of the counter-rotating turbines (0.068-m rotor diameter) was measured and compared with that of a single turbine of the same size. Experimental results show the tendency of power production enhancement of different counter-rotating configurations. Additionally, the two-dimensional (2D) turbine wakes and blade hydrodynamic interactions were simulated by the shear stress transport k-omega (SST k-omega) model using OpenFOAM. The computational domain included a stationary region and two rotating regions (for the case of counter-rotating turbines) set at constant angular velocities. The interface between the rotating and stationary region was modeled as separated surface boundaries sliding on each other. Velocity, pressure, turbulent kinetic energy, eddy viscosity, and specific dissipation rate field were interpolated between these boundaries.

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羽ばたき翼の回内・回外運動が揚力発生に及ぼす影響に関する実験的研究

近藤貴之，小尾晋之介

流体工学部門講演会講演論文集 2018, OS13-6 2018

弾性変形する平板の形状と自己推進速度に関する実験的研究

池田曉，馬場直道，小尾晋之介

流体工学部門講演会講演論文集 2018, OS13-7 2018

乱流境界層に置かれた円柱前部の四面体による馬蹄形渦への影響

吉井慎太郎，小尾晋之介

流体工学部門講演会講演論文集 2018, OS1-17 2018

アーム付 HDD モデルにおけるシュラウド内壁面の変動圧力計測

真田航平，小尾晋之介

IIP 情報・知能・精密機器部門講演会講演論文集 2018, 1C13_1 2018

Measurement of the fluctuating pressure on the shroud wall of a hard-disk drive model

Sonoda Y., Sanada K., Obi S.

TURBULENCE HEAT AND MASS TRANSFER 9 (THMT-18) (Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer) 2018-July 689 - 698 2018

ISSN 2377-2816

The present study aims at clarifying the turbulent structure developing in a hard disk drive through the measurement of fluctuating pressure on the shroud wall. The measurements have been conducted in two different models, with and without read-write arms, and the results are compared to characterize the effect of the internal structure of turbulent flow on the device. The effect of read-write arms is found to be of primary importance, as it changes the flow structure drastically, with the increasing the arm insertion angle. The most pronounced effect has been found in the gradual change of the characteristic frequency in the power spectrum density of the pressure fluctuation: Both qualitative and quantitative changes are observed.

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Development of a Mechanical Engineering Test Item Bank to promote learning outcomes-based education in Japanese and Indonesian higher education institutions

Jeffrey S. Cross, Estiyanti Ekawati, Satoko Fukahori, Shinnosuke Obi, Yugo Saito, Nathanael P. Tandian, and Farid Triawan

Tuning Journal for Higher Education (University of Deusto) 5 ( 1 ) 41 - 73 2017.11

Research paper (scientific journal), Joint Work, Accepted, ISSN 2340-8170

Following on the 2008-2012 OECD Assessment of Higher Education Learning Outcomes (AHELO) feasibility study of civil engineering, in Japan a mechanical engineering learning outcomes assessment working group was established within the National Institute of Education Research (NIER), which became the Tuning National Center for Japan. The purpose of the project is to develop among engineering faculty members, common understandings of engineering learning outcomes, through the collaborative process of test item development, scoring, and sharing of results. By substantiating abstract level learning outcomes into concrete level learning outcomes that are attainable and assessable, and through measuring and comparing the students’ achievement of learning outcomes, it is anticipated that faculty members will be able to draw practical implications for educational improvement at the program and course levels. The development of a mechanical engineering test item bank began with testscale test implementation in 2016 of 348 first semester master’s students in 9
institutions in Japan, using both multiple choice questions designed to measure the
mastery of basic and engineering sciences, and a constructive response task designed
to measure “how well students can think like an engineer.” The same set of test items
were translated from Japanese into to English and Indonesian, and used to measure
achievement of learning outcomes at Indonesia’s Institut Teknologi Bandung (ITB)
on 37 rising fourth year undergraduate students. This paper highlights how learning
outcomes assessment can effectively facilitate learning outcomes-based education, by
documenting the experience of Japanese and Indonesian mechanical engineering
faculty members engaged in the NIER Test Item Bank project.

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A smooth partition of unity finite element method for vortex particle regularization

KIRCHHART MATTHIAS, OBI SHINNOSUKE

SIAM Journal of Scientific Computing (SIAM Journal on Scientific Computing) 39 ( 5 ) A2345 - A2364 2017.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 10648275

We present a new class of C∞-smooth finite element spaces on Cartesian grids, based on a partition of unity approach. We use these spaces to construct smooth approximations of particle fields, i.e., finite sums of weighted Dirac deltas. In order to use the spaces on general domains, we propose a fictitious domain formulation, together with a new high-order accurate stabilization. Stability, convergence, and conservation properties of the scheme are established. Numerical experiments confirm the analysis and show that the Cartesian grid-size should be taken proportional to the square-root of the particle spacing h, resulting in significant speed-ups in vortex methods.

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A Splitting-free Vorticity Redistribution Method

KIRCHHART MATTHIAS, OBI SHINNOSUKE

Journal of Computational Physics (Elsevier) 330 282 - 295 2017.02

Research paper (scientific journal), Joint Work, ISSN 0021--9991

We present a splitting-free variant of the vorticity redistribution method. Spatial consis-tency and stability when combined with a time-stepping scheme are proven. We propose a new strategy preventing excessive growth in the number of particles while retaining the order of consistency. The novel concept of small neighbourhoods significantly reduces the method’s computational cost. In numerical experiments the method showed second order convergence, one order higher than predicted by the analysis. Compared to the fast multipole code used in the velocity computation, the method is about three times faster.

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Internal Regulation to Promote Internationalization of University

OBI SHINNOSUKE

KEIO SFC JOURNAL (慶應義塾大学湘南藤沢学会) 17 ( 2 ) 6 - 11 2017

Single Work

It is of great importance for universities to introduce internal regulations which allow flexible student mobility when the promotion of internationalization is considered. Through the activity of EBA Consortium, a new status for
international student has been settled, so that students can come and leave at any time regardless of the academic calendar. For Japanese students to leave during the study at the university, the problems due to discrepancy in academic calendar could be partially resolved by introducing four-term system. The appropriate design of such regulation should be conducted in accordance with the global picture of the academic activities in consortium to avoid local optimization.

Flow Control over Swept Wings Using Nanosecond-pulse Plasma Actuator

KATO KENTARO, BEREITSAMTER CHRISTIAN, OBI SHINNOSUKE

International Journal of Heat and Fluid Flow (Elsevier) 61, PartA 58 - 67 2016.10

Research paper (scientific journal), Joint Work, ISSN 0142-727X

An experimental study aiming at lift enhancement of a swept wing by using a plasma actuation driven by repetitive nanosecond-pulse voltage was carried out. The periodic plasma actuation was applied near the apex in order to manipulate the leading edge vortices in the post-stall regime.The velocity field in the wake was measured by means of stereoscopic particle image velocimetry and was evaluated based on control volume analysis. The results indicated that the change in the intensity of the streamwise vortex led to the lift enhancement.

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1E43 動脈瘤治療を目的としたパイプラインステントの流動解析

小尾晋之介，立嶋智

バイオエンジニアリング講演会講演論文集 2016.28, _1E43-1_-_1E43-5_ 2016

HDD モデル内壁面における変動圧力計測

正本佳，中村庸義，小尾晋之介

IIP 情報・知能・精密機器部門講演会講演論文集 2016, B-1-1 2016

HDD 内乱流場におかれたアームに作用する流体力の数値シミュレーション

田丸明裕，小尾晋之介

IIP 情報・知能・精密機器部門講演会講演論文集 2016, B-1-2 2016

Evaluation of Pressure Field Based on the Velocity Measurement by PIV

OBI SHINNOSUKE

Turbomachinery (Turbomachinery Society of Japan) 43 ( 11 ) 686 - 691 2015.11

Research paper (scientific journal), Single Work

Space-time pressure-velocity correlations in a turbulent boundary layer

NAKA YOSHITSUGU, STANISLAS MICHEL, FOUCAUT JEAN-MARC, COUDERT SEBASTIEN, LAVAL JEAN-PHILIPPE, OBI SHINNOSUKE

Journal of Fluid Mechanics (Cambridge University Press) 771 624 - 675 2015.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 00221120

The spatio-temporal pressure-velocity correlation in a turbulent boundary layer is investigated to try to understand the link between pressure uctuations and turbulent coherent structures. A new experimental setup is developed to measure the pressure fluctuations at the wall and in the field, and the velocityfield by stereo PIV simultaneously. For the pressure fluctuations in the field, the pressure-velocity correlations Rpu and Rpw exhibit a meaningful correlation in a region extended in time in addition to the structures observed with the wall pressure. The structure of the diffrent correlations observed can be linked to the LSM and VLSM put previoulsly in evidence by diffrent authors.

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11017 半円オリフィス管内乱流のステレオ PIV 計測

小尾晋之介，安岡佳紀

日本機械学会関東支部総会講演会講演論文集 2015.21, _11017-1_-_11017-2_ 2015

11001 平板往復運動の誘起する渦流れ構造と力の渦法による数値解析

国井悠介，日置史記，小尾晋之介

日本機械学会関東支部総会講演会講演論文集 2015.21, _11001-1_-_11001-2_ 2015

0702 移動平板の誘起する渦流れ構造と力の渦法による数値解析

國井悠介，日置史紀，小尾晋之介

流体工学部門講演会講演論文集 2015, _0702-1_-_0702-5_ 2015

0616 ナノ秒パルスプラズマアクチュエータを用いた翼上の流れ制御のための数値モデル

加藤賢太郎，小尾晋之介

流体工学部門講演会講演論文集 2015, _0616-1_-_0616-3_ 2015

0201 半円オリフィス管内乱流のステレオ PIV 計測及び壁面静圧計測

安岡佳紀，小尾晋之介

流体工学部門講演会講演論文集 2015, _0201-1_-_0201-3_ 2015

PIV 速度データに基づく圧力場の推定方法 (特集光応用計測の Cutting Edge)

小尾晋之介

ターボ機械 43 (11), 686-691 2015

LES study of the turbulent flow in a HDD model

Tamaru A., Obi S.

Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer (Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer) 0 859 - 862 2015

ISSN 26425629

Turbulent flow in a hard disk drive model which contained two disks and a RW (read-and-write) arm was numerically analyzed at a disk rotation Reynolds number of about 105. The evaluation of the fluctuating torque revealed that the RW arm may be oscillated at a frequency which had only weak correlation with the disk rotation speed. The fluctuating pressure was stronger on the leeward surface of the RW than that of the windward. It was further indicated that the fluctuating torque on the RW arm was weakly correlated with the surface pressure fluctuation on the shroud wall.

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Three-dimensional turbulent recirculating flow in a pipe with semi-circular orifice

Yasuoka Y., Obi S.

Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer (Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer) 0 203 - 206 2015

ISSN 26425629

Experimental study on the turbulent flow in a circular pipe with a semi-circular orifice has been conducted. The velocity was measured by a stereo PIV system that provided the three components of mean velocity in as well as six components of the Reynolds stress on the cross section of the pipe at different streamwise locations. The oncoming flow was confirmed to be a typical fully developed turbulent flow. The flow behind the semi-circular orifice was found to be strongly turbulent, associated with secondary flow. The ambiguity in the experiments was carefully addressed, and it was found that the measurement conducted either with or without the orifice was found to be equally accurate.

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Flow Separation Control over a Gö 387 Airfoil by Nanosecond Pulse-Periodic Discharge

KATO KENTARO, CHRISTIAN BREITSAMTER, OBI SHINNOSUKE

Experiments in Fluids (Springer) 55 ( 8 ) 1795 2014.08

Research paper (scientific journal), Joint Work, Accepted, ISSN 07234864

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An attempt to measure fluctuating local pressure in free turbulent flow in water

KAWATA TAKUYA, MAEDA HOSHITO, OBI SHINNOSUKE

Journal of Fluid Science and Technology (Japan Society of Mechanical Engineers) 9 ( 2 ) 2014.07

Research paper (scientific journal), Joint Work, Accepted

We developed a technique for the measurement of fluctuating hydraulic-pressure at an arbitrary point in turbulent
flow. A pressure-measuring system was composed of a miniature static-pressure probe (SP-probe), a strain-gagetype
pressure transducer, and a tube connecting them. A model equation of dynamic response of the pressuremeasuring
system was introduced, and a calibration technique for determining parameters in the model equation
was developed. Effects of the size of the SP-probe, length of the tube, and sensitivity of the pressure sensor were
systematically investigated using several SP-probes, tubes, and pressure transducers with different sizes, lengths,
and sensitivities, and fluctuating hydraulic-pressure measurement was performed in a wake of a circular cylinder

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Velocity-pressure correlation measurement based on planar PIV and miniature static-pressure probes

KAWATA TAKUYA、OBI SHINNOSUKE

Experiments in Fluids (Springer) 55 ( 7 ) 1776 2014.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 07234864

This study aimed to measure the pressure-related turbulent statistics such as the velocity-pressure correlation or the pressure-strain correlation.
To do so, direct single-point-measurement by a miniature static-pressure probe (SP-probe) and the evaluation of instantaneous pressure field based on the PIV measurement were combined.
The instantaneous pressure field was derived from the measurement results by the PIV, and the pressure fluctuation associated with the large-scale vortex motion was extracted using reference signals directly measured by the SP-probe.
The measurement was performed in a turbulent near wake of a circular cylinder.
After the validity of the instantaneous pressure evaluated from the PIV data was addressed, the velocity-pressure correlation and the pressure-strain correlation were investigated.

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Simultaneous measurement of fluctuating velocity and pressure in the near wake of a circular cylinder

KAWATA TAKUYA, NAKA YOSHITSUGU, OBI SHINNOSUKE

Experiments in Fluids (Springer) 55 ( 5 ) 1731 2014.05

Research paper (scientific journal), Joint Work, ISSN 07234864

Simultaneous measurement of fluctuating velocity and pressure by a static-pressure probe and a hot-wire probe was performed in the near wake of a circular cylinder, in order to strengthen reliability of the measurement technique. Effect of geometry of the static-pressure probe was systematically investigated, and validity of the measurement results was addressed by quantitative comparison with reference data by a large-eddy simulation. Interference between the probes was found to mainly depend on the diameter of the pressure probe and only weakly on the length. A certain time lag between the velocity and pressure signals was detected in the experiment, and the measurement results of velocity-pressure correlation up ̄ and vp ̄ obtained with the correction of the time lag were in good agreement with the computational results. It was also found that the measurement of vp ̄ is extremely sensitive to a small time lag between the velocity and pressure signals, while that of up ̄ is not. © 2014 Springer-Verlag Berlin Heidelberg.

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S0550302 ナノ秒パルスプラズマアクチュエータによる矩形翼, 後退翼上における流体制御 ([S055-03] プラズマアクチュエータ (3))

加藤賢太郎，小尾晋之介

年次大会 2014, _S0550302--_S0550302- 2014

7・3 乱流 (7. 流体工学,< 特集> 機械工学年鑑)

小尾晋之介

日本機械学会誌 117 (1149), 521 2014

LES Study of Flow between Shrouded Co-rotating Disks

WASHIZU TOMOYA, LUBISCH FLORIAN, OBI SHINNOSUKE

Flow, Turbulence and Combustion (Flow, Turbulence and Combustion) 91 ( 3 ) 607 - 621 2013.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 1386-6184

Large eddy simulations of turbulent flow between shrouded co-rotating disks, representing a simplified model of a hard disk drive, are performed. The computation domain surrounds a complete disk and is bounded at top and bottom by half a disk. Therefore, it is possible to compute the fluctuating pressure field surrounding the middle disk.
Also, the influence of the shroud geometry is taken into account by comparing a flat shroud wall and a wall with rib chambers. In the flat shroud case, the fluctuating pressure on the upper- and lower-surface of a disk indicates a strong correlation with fluid motion travelling across the disk-tip clearance region. However, in the ribbed shroud case the organized flow structure that is observed in the flat shroud case disappears and the fluctuating pressure acting on the surface of the disk is remarkably diminished.

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An experimental study on the flow behavior near the read-and-write arm in a hard disk drive model with a shroud opening

SHIRAI KATSUAKI, BUETTNER LARS, OBI SHINNOSUKE, CZARSKE JUERGEN

Microsystem Technologies (Microsystem Technologies) 19 ( 9-10 ) 1519 - 1527 2013.09

Research paper (scientific journal), Joint Work, Accepted, ISSN 0946-7076

Complex flow inside a hard disk drive (HDD) was investigated using a simplified 3.5in model for clarifying
the mechanism causing flow-induced vibration. Flow measurements were carried out with a test rig which consisted of transparent disks, RWA and covers. The high
spatial resolution of the results was achieved using a laser
Doppler velocity profile sensor with a physical resolution
in micrometers and a velocity uncertainty of 0.2 %. The resulting velocity statistics exhibit turbulent Couette-like flow in the narrow 1 mm space between the disks and the RWA.

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Simulation and PIV experiment of the ducted water current turbine and extremely low had helical turbine

SOUNTHISACK PHOMMACHANH, OBI SHINNOSUKE, PRIYONO SUTIKNO, ARYADI SOEWONO

ASEAN Engineering Journal Part A (AUN/SEED-Net) 3 ( 2 ) 54-69 2013.09

Research paper (scientific journal), Joint Work, Accepted, ISSN 2229-127X

0617 時間分解 PIV と小型静圧プローブを用いた速度・圧力相関計測 (OS6-4 噴流, 後流およびはく離流れ現象の探求と先端的応用, OS6 噴流, 後流およびはく離流れ現象の探求と先端的応用)

河田卓也，前田星秀，小尾晋之介

流体工学部門講演会講演論文集 2013, _0617-01_-_0617-02_ 2013

1102 円筒容器内回転積層円盤間乱流における圧力変動とディスク振動の同時計測 (OS11-1 流体関連振動・騒音, OS11 流体関連振動・騒音)

高橋昌之，小尾晋之介，河田卓也

流体工学部門講演会講演論文集 2013, _1102-01_-_1102-02_ 2013

0639 自由せん断乱流中の局所圧力変動の計測 (OS6-8 噴流, 後流およびはく離流れ現象の探求と先端的応用, OS6 噴流, 後流およびはく離流れ現象の探求と先端的応用)

前田星透，河田卓也，小尾晋之介

流体工学部門講演会講演論文集 2013, _0639-01_-_0639-02_ 2013

Simultaneous measurment of fluctuating velocity and pressure using time-resolved PIV and miniature static-pressure probes

Kawata T., Obi S.

International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013 (International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013) 2 2013

ISSN 9780000000002

Simultaneous measurement of the fluctuating velocity and pressure is performed combining a miniature staticpressure probe and a time-resolved PIV aiming at further improvement in evaluation of the velocity-pressure correlation. Two static-pressure probes were placed in the measurement domain of the time-resolved PIV and the instantaneous velocity field and the fluctuating velocity are measured simultaneously. The instantaneous pressure filed is estimated from the measured velocity field by numerically solving a discrete Poisson equation for pressure. The values of the estimated pressure are corrected based on the pressure values which are directly measured by the static-pressure probe.

An attempt to evaluate pressure force on a flapping rigid plate using velocity data of PIV measurements

ALEXANDRE SURYADI, OBI SHINNOSUKE

ASEAN Engineering Journal 2 ( 1 ) 30-44 2012.06

Research paper (scientific journal), Joint Work

The flow field generated by a sinusoidally flapping rigid flat plate was measured using stereo particle image velocimetry to estimate the pressure field on two cross sections of the flapping plate. The pressure field was estimated by integrating the three–dimensional Poisson equation derived from the Euler equation. The solution of this Poisson equation is obtained as a function of the measured phase-averaged velocity field. Simultaneous to PIV measurements, the torque on the flapping axis, which depicts the forces acting on the wing, was measured using strain gauges. The maximum torque coefficients, observed from both methods, of each cycle are delayed from the maximum acceleration of the plate. One of the factors of the phase delay is attributed to the separation of vortex structure along the edges of the plate. After the separation point the increase of pressure drag is delayed relative to the flapping motion. At the same phase, vortex structure is generated on the leeward side of the plate at the free end. Low pressure region was observed on the leeward side of the plate which further add to the pressure drag.

1009 移動壁面を有する密閉容器内流れの渦法解析 (OS10 渦流れのダイナミクス, オーガナイズドセッション)

宮内新喜，小尾晋之介

流体工学部門講演会講演論文集 2012, 389-390 2012

Experimental and numerical investigation on a fully developed turbulent pipe flow over a semicircle orifice

Okuda S., Lepeut C.H., Rasti M., Kawata T., Obi S.

Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer (Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer) 2012-September 2504 - 2512 2012

The internal separated flow associated with remarkable mean secondary flow is investigated both experimentally and computationally. The computational investigation indicates that the commercially available RANS model group and LES provide obvious difference in terms of the prediction of the flow reattachment and recovery. On the other hand, some over-proportional magnitude of the velocity fluctuation across the mean flow direction is found by velocity measurement by stereo PIV. The recirculation region in either side of the orifice seems to be the source of the streamwise vortex that governs the development of the flow near the flow reattachment point. The considered flow serves as a useful test case for both RANS modeling and LES.

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Simultaneous measurement of fluctuating velocity and pressure using stereo-PIV and static-pressure probe in a turbulent wing-tip vortex

Kawata T., Obi S.

Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer (Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer) 2012-September 2311 - 2320 2012

Simultaneous measurement of the fluctuating pressure and velocity field is performed combining a miniature static-pressure probe and a stereo-PIV. The static-pressure probe is placed just behind the velocity measuring plane illuminated by the laser sheet, and the instantaneous velocity field and the fluctuating pressure are measured simultaneously in a turbulent wing-tip vortex flow. The instantaneous pressure field is estimated by numerically solving a discrete two-dimensional Poisson equation for pressure. The result is compared with directly measured pressure for validation.

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The estimation of pressure on the surface of a flapping rigid plate by stereo PIV

Suryadi A., Obi S.

Experiments in Fluids (Experiments in Fluids) 51 ( 5 ) 1403 - 1416 2011.11

ISSN 07234864

The method to estimate the dynamic load of a flapping wing by the integration of pressure on the wing's surface is discussed. The flapping wing was modeled as a plate flapping sinusoidally in hovering condition. The flow around the flapping plate was measured using stereo PIV on multiple measurement planes along the out-of-plane direction. The phase-averaged velocity field of each measurement plane was calculated so that three-dimensional analyses could be applied. The phase-averaged pressure field was obtained from the integration of the three-dimensional Poisson equation for pressure using the available information acquired from stereo PIV measurements. The pressure field is visualized on the measurement planes. In this study, the estimated load was the torque of the axis of rotation. This torque was compared with the result from strain gauge measurements. The torque estimation, although only on a partial surface of the plate, is within reasonable agreement with the measured torque. The integration of the Poisson equation based on stereo PIV measurements and estimations of the torque shows that an increase in the torque at the start of a flapping stroke is caused by the stagnation on the surface of the plate from the flow that is induced by the leading-edge vortices. © 2011 Springer-Verlag.

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Estimation of pressure on the surface of a flapping rigid plate by stereo PIV

SURYADI ALEXANDRE, OBI SHINNOSUKE

Experiments in Fluids (Springer) 51 ( 5 ) 1403-1416 2011.10

Research paper (scientific journal), Joint Work, Accepted

The method to estimate the dynamic load of a flapping wing by the integration of pressure on the wing's surface is discussed. The flapping wing was modeled as a plate flapping sinusoidally in hovering condition. The phase-averaged pressure field was obtained from the integration of the three-dimensional Poisson equation for pressure using the available information acquired from stereo PIV measurements. The torque estimation, although only on a partial surface of the plate, is within reasonable agreement with the measured torque.

Simultaneous measurements of disk vibration and pressure fluctuation in turbulent flow developing in a model hard disk drive

KURASHIMA DAISUKE, NAKA YOSHITSUGU, FUKAGATA KOJI, OBI SHINNOSUKE

International Journal of Heat and Fluid Flow (Elsevier) 32 ( 3 ) 567–574 - 574 2011.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 0142727X

The complex flow features inside hard disk drive models are investigated in an axisymmetric and a semi-open shroud configurations.
For the axisymmetric case, we have employed both experimental and computational approaches.
The experiment focuses on both flow dynamics and the disk vibration, where measurements of the fluctuating pressure and velocity are undertaken at some representative points.
The correlation between the disk vibration and the fluctuating pressure in the turbulent flow between disks is evident from the spectral analysis.
The experimentally observed fluctuating pressure and velocity are partly due to the disk vibration and its contribution could be estimated by comparing the experiment with the results of a large eddy simulation.
For the semi-open shroud case, although the characteristic peaks attributable to the large-scale vortical structure are still observed in the power spectra, the pressure fluctuation and the disk vibration are suppressed when the arm is inserted.

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Simultaneous measurement of velocity and fluctuating pressure in a turbulent wing-tip vortex using triple hot-film sensor and miniature total pressure probe

Kawata Takuya, Naka Yoshitsugu, Fukagata Koji, Obi Shinnosuke

Flow, Turbulence and Combustion 86 ( 3-4 ) 419 - 437 2011.04

ISSN 1386-6184

We have developed a probe-system for simultaneous measurement of three velocity components and pressure in turbulent flows. A miniature total pressure probe is placed adjacent to the sensors of a triple hot-film probe in order to achieve the spatial resolution which is equivalent to that of the triple hot-film probe itself. The instantaneous static pressure is calculated from measured velocity and total pressure by means of a newly developed processing method based on the Bernoulli equation for unsteady flows. The measurements were undertaken in a turbulent wing-tip vortex flow. The look-up table method is employed for the calibration of the hot-film probe so accurate velocity data could be obtained over a wide range of the flow-attack angles. It is also demonstrated that the present probe-system is capable of measuring fluctuations in both velocity and pressure in the 20-650 Hz frequency range. The distribution of the fluctuating pressure obtained by this indirect method is in good agreement with the results from direct measurements of static pressure, demonstrating the promising performance of the present method. Furthermore, an improvement in the ability to make measurements of the velocity-pressure correlation across the wing-tip vortex is achieved. This improvement is possible because the effects of lateral velocity components are properly taken into account in the present formulation. The investigation regarding the transport equation budget for turbulent kinetic energy shows an anomalous structure of turbulence in this flow, mainly due to the meandering of the vortex, and the measurement of pressure diffusion is found to play an important role in the characterization of this kind of flow. © 2010 Springer Science+Business Media B.V.

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Highly spatially resolving laser Doppler velocity measurements of the tip clearance flow inside a hard disk drive model

SHIRAI KATSUAKI, YAGUCHI YUSUKE, BUETTNER LARS, CZARSKE JUERGEN, OBI SHINNOSUKE

Experiments in Fluids (Springer) 50 ( 3 ) 573-586 - 586 2011.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 07234864

The flow in the tip clearance of a hard disk drive model has been investigated with laser Doppler techniques. The flow was driven by co-rotating disks inside a cylindrical enclosure in order to simulate a hard disk drive used for data storage devices. The main focus of the investigation was on the understanding of complex flow behavior in the narrow gap region between the disk tip and the outer shroud wall, which is supposed to be one of the causes of flow induced vibration of the disks. Experiments in the past have never been able to examine this region because of the lack of the spatial resolution of sensors in the highly three dimensional flow in the region. In the present investigation, the flow velocity in the tip clearance region was measured with optical measurement techniques for the first time.

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Simultaneous measurement of velocity and fluctuating pressure in a turbulent wing-tip vortex using triple hot-film sensor and miniature total pressure probe

KAWATA TAKUYA, NAKA YOSHITSUGU, FUKAGATA KOJI, OBI SHINNOSUKE

Flow, Turbulence and Combustion (Springer) 86 ( 3-4 ) 419-437 2011.03

Research paper (scientific journal), Joint Work

We have developed a probe-system for simultaneous measurement of three velocity components and pressure in turbulent flows. A miniature total pressure probe is placed adjacent to the sensors of a triple hot-film probe in order to achieve the spatial resolution which is equivalent to that of the triple hot-film probe itself. The investigation regarding the transport equation budget for turbulent kinetic energy shows an anomalous structure of turbulence in this flow, mainly due to the meandering of the vortex, and the measurement of pressure diffusion is found to play an important role in the characterization of this
kind of flow.

Vortex Methods for the Simulation of Turbulent Flows: Review

YOKOTA RIO, OBI SHINNOSUKE

Journal of Flow Science and Technology (Japan Society of Mechanical Engineers) 6 ( 1 ) 14-29 2011.01

Research paper (scientific journal), Joint Work, Accepted

Vortex methods are a group of Lagrangian and semi-Lagrangian methods based on the vorticity-streamfunction or vorticity-velocity formulation of the Navier-Stokes equation, and provide an interesting alternative to grid based methods for external flows dominated by unsteady vortical motion. In the present review article, we will assess the advantages and disadvantages of vortex methods for the simulation of incompressible turbulent flows, based on the speed and accuracy benchmarks that have been performed recently. Our goal is to objectively and quantitatively evaluate the performance of this non-standard method, by directly comparing it's speed and accuracy against finite difference and pseudo-spectral DNS codes under identical calculation conditions. We also present examples of vortex methods in engineering applications of turbulent flows.

Experimental investigation of the complex flow behavior in a hard disk drive model

Shirai Katsuaki, Büttner Lars, Czarske Jürgen, Shiga Nobuo, Obi Shinnosuke

ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 (ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011) 7 ( PARTS A AND B ) 1077 - 1084 2011

ISSN 9780791854938

Flow inside a hard-disk drive (HDD) is investigated using a simplified 3.5″ HDD model with shroud opening and read-and-write arm (RWA). The model is designed to serve as a benchmark of HDD flow study both in experiments and in numerical simulations. The complex flow behavior in the narrow disk-to-disk space is focused with the RWA inserted into the space. The velocity statistics are acquired at totally 8 different locations using a velocity profile sensor with a spatial slot resolution of 30 μm along the axial direction. The measurement was carried out at the disk Reynolds number Re_d=2. 4×10⁵ which corresponds to the rotation speed of 7700 rpm at a real 3.5″ HDD for desktop computers. The resulting mean velocities and Reynolds stress components are influenced by the shroud opening and especially by the RWA, compared to an axisymmetric model without an RWA. The highly sheared flow between the RWA and adjacent upper/lower disk was successfully captured in the experiment. Copyright © 2011 by ASME.

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Effect of surface character on proliferation and adhesion of l929 fibroblast

Nagat Atsushi, Miyata Shogo, Saito Mario, Komotori Jun, Obi Shinnosuke, Naiviba Yoji, Koyaivia Tadayoshi

Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A (Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A) 77 ( 775 ) 544 - 551 2011

ISSN 0387-5008

In this study, the effects of Fine Particle Peemng (FPP) treatment on adhesion and proliferation in L929 fibroblast were investigated. FPP treatments were performed on the Ti-6A1-4V alloy specimen by using Ti0 ₂ (T series) , glass beads (G series) and Alumina (Al series) shot particle. The polished specimen (P series) was also prepaid. Cell culture tests on the specimen were carried out with L929 fibroblast after 6 hours, 1, 3 and 5 days culture. Cell proliferation was evaluated by counting the number of cells by MTT assay. Cell adhesion strength was also measured by counting the number of cells detached by fluid-induced shear stress. The FPP treated surface by using shot particle of varied materials, which have different surface character. The Ti02 series showed good cell proliferation. This was because the protein adsorption of Ti0 ₂ series encourage cell adhesion. The detachment cells on the specimen were observed after share stress loading. The FPP treated series showed good cell adhesion. This was because the microscopically surface topography encourage cell adhesion.

速度・圧力相関計測に対して静圧プローブの形状が与える影響

河田卓也，中吉嗣，深潟康二，小尾晋之介

理論応用力学講演会講演論文集第 60 回理論応用力学講演会, 84-84 2011

ヒービング運動する弾性板周りの PIV 計測

加藤賢太郎，小尾晋之介

理論応用力学講演会講演論文集第 60 回理論応用力学講演会, 247-247 2011

HDD 狭隘部乱流のレーザープロファイルセンサーによる速度計測 (磁気記録・情報ストレージ)

白井克明，志賀信雄，ビュットナーラース，チャルスケユルゲン，小尾晋之介

電子情報通信学会技術研究報告: 信学技報 111 (307), 1-8 2011

L929 線維芽細胞の増殖性と接着性に及ぼす基材表面の微細凹凸形状の影響

長井篤，宮田昌悟，斉藤万里雄，小茂鳥潤，小尾晋之介，難波洋司， ...

日本機械学会論文集 A 編 77 (775), 544-551 2011

On reformulating the erm-based second-moment closure towards a more robust turbulence model

Hui J., Obi S., Jakirlic S.

7th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2011 (7th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2011) 2011-July 2011

The present study considers a reformulation of the Durbin's (1993) ERM-based second-moment closure model aiming at reduction of the numerical stiffness originating from the wall boundary conditions. The reformulation performed represents an analogy to the procedure Hanjalic et al. (2004) proposed when deriving the eddy-viscosity-based ζ − f model. The presently reformulated model alternatively solves the transport equations for the ratio of the Reynolds stress components to turbulent kinetic energy ζij = uiuj/k, instead of equations governing the Reynolds stress tensor. It is believed that the boundary conditions of the newly derived elliptic relaxation equations will contribute to the numerical robustness of the model with respect to the immediate wall vicinity. Another advantage, analogously to the Hanjalic's et al. ζ − f model, is the appearance of the Reynolds stress production rate (representing an exact formulation) in the ζij equations instead of dissipation rate ε (originating from the corresponding model equation). Application of the present model formulation to a plane channel flow in a range of Reynolds numbers up to Reτ = 2003 results in a good agreement with available DNS database.

Velocity-pressure correlation measurement using various static-pressure probes in a wake of a circular cylinder

Kawata T., Naka Y., Fukagata K., Obi S.

7th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2011 (7th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2011) 2011-July 2011

In the present study, an experimental investigation is conducted into the effect of the shape of a miniature staticpressure probe on the velocity-pressure correlation measurement. Ten static-pressure probes, with systematicallychanged probe diameters and lengths, are compared in combination with an X-type hot-wire probe to examine the accuracy of the simultaneous measurement of the fluctuating velocity and pressure. The effect of the probe shape on the distance between the probes, which is necessary to avoid interference, is also investigated for the various pressure probes, and it is found that the change in probe diameter has the primary influence on the probe interference. In the velocity-pressure correlation measurements, the results of the pressure fluctuation p' and the velocity-pressure correlation up are not affected by the probe shape. On the other hand, it is indicated that the measurement of vp is extremely sensitive to the configuration of the pressure holes including its orientation.

Stereo PIV measurement of a finite, flapping rigid plate in hovering condition

SURYADI ALEXANDRE, ISHII TAKAYUKI, OBI SHINNOSUKE

Experiments in Fluids (Springer) 49 ( 2 ) 447-460 - 460 2010.08

Research paper (scientific journal), Joint Work, Accepted, ISSN 07234864

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Numerical Investigations on Leakage Performance of the Rotating Labyrinth Honeycomb Seal

LI JUN, KONG SHENGRU, YAN XIN, OBI SHINNOSUKE, FENG ZHENGPING

Journal of Engineering for Gas Turbines and Power - Transactions of the ASME (Journal of Engineering for Gas Turbines and Power) 132 ( 6 ) 062501 - 1 2010.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 07424795

Three-dimensional Reynolds-averaged Navier-Stokes (RANS) solutions from CFX were utilized to investigate the leakage flow characteristics in the labyrinth honeycomb seal of steam turbines. At first, the accuracy and reliability of the utilized RANS approach was demonstrated using the published experimental data of the honeycomb seal. It showed that the utilized numerical method has sufficient precision to predict the leakage performance in seals. Then a range of sealing clearances, cell diameters, cell depths, rotation speeds, and pressure ratios were investigated to determine how these factors affect the leakage flow rate of the labyrinth honeycomb seal.

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Comparing vortex methods and finite difference methods in a homogeneous shear flow

YOKOTA RIO & OBI SHINNOSUKE

International Journal for Numerical Methods in Fluids (John Wiley and Sons Ltd.) 63 ( 7 ) 828-846 2010.05

Research paper (scientific journal), Joint Work, Accepted

Acceleration of bluff body calculation using MDGRAPE-2

Sheel T. K., Obi S.

International Journal of Engineering, Transactions A: Basics (International Journal of Engineering, Transactions A: Basics) 23 ( 2 ) 169 - 176 2010.04

ISSN 1025-2495

Bluff body calculation was accelerated by using a special-purpose computer, MDGRAPE-2, that was exclusively designed for molecular dynamics simulations. The three main issues were solved regarding the implementation of the MDGRAPE-2 on vortex methods. These issues were the efficient calculation of the Biot-Savart and stretching equation, the optimization of the table domain, and the round-off error caused by the partially single precision calculation in the MDGRAPE-2. Finally this technique was applied to calculation of flow around a circular cylinder. The drag and lift coefficient was investigated to check the validity of the proposed method.

Near-field development of a turbulent mixing layer periodically forced by a bimorph PVDF film actuator

NAKA YOSHITSUGU, TSUBOI KEN-ICHIRO, KAMETANI YUKINORI, FUKAGATA KOJI, OBI SHINNOSUKE

Journal of Fluid Science and Technology (JSME) 5 ( 2 ) 156-168 2010.03

Research paper (scientific journal), Joint Work, Accepted

We have performed experiments in a turbulent mixing layer with periodic forcing introduced by a Piezo Film Actuator (PFA). Three dierent lengths of PFAs have been used, and the eects of various combinations of forcing amplitudes and frequencies are investigated. By forcing at the natural and its first sub-harmonic frequencies, two counter-rotating vortices are clearly observed in one
period of forcing. By forcing at second sub-harmonic frequency, the vortical structure is found only in the downstream region.

High-performance computing techniques for vortex method calculations

SHEEL TARUN KUMAR & OBI SHINNOSUKE

Theoretical and Computational Fluid Dynamics (Springer) 24 ( 1-4 ) 175-179 - 179 2010.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 09354964

A fast vortex method has been developed by using a special-purpose computer, MDGRAPE-3. MDGRAPE-3, successor of MDGRAPE-2, has been applied to the same calculations (Sheel et al. in Comput. Fluids 36:1319–1326, 2007) and the improvement in speed was 1000 times faster when compared with the ordinary PC Xeon 5160 (3.0 GHz) for N = 1E6. The simultaneous use of the fast multipole method, Pseudoparticle multipole method with the special-purpose computers gives further acceleration of vortex method
calculations. In addition, performances and efficiency have been investigated carefully. Further possibility has
been investigated carefully and compared the present result with the previous one.

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Duct water current turbine and extremely low head helical turbine

Phommachanh Sounthisack, Sutikno Priyono, Shinnosuke Obi

AIP Conference Proceedings (AIP Conference Proceedings) 1225 213 - 224 2010

ISSN 9780735407695

This research introduces the Duct Water Current Turbine Triple Helix with very low head less than 2m and water current at river or in the ocean, economical ecological use for small hydro power rating between 100 to 1000 kW still represents an unsolved problem. Unlike conventional hydro installation, water current turbine in open flow and generate power from flowing water with almost zero in environmental impact. Developments in water current turbine design are reviewed and some potential advantages of duct or "diffuser augmented" current turbine and extremely low head turbine will be explored. For the output expected from the project is helical turbine with control flow on duct. The research aims to apply the helical turbine inside the duct to find the parameter of the power coefficient against tip speed ratio λ, pitch angle and twist angle y which is also the optimum parameter to design a helical cross flow turbine with duct. Parameters are obtained from numerical simulation and through the experimental result. For ducted turbines the theoretical limit depends on (i) the pressure difference that can be created between duct inlet and outlet, and (ii) the volumetric flow through the duct. © 2010 American Institute of Physics.

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ロバスト性向上を目指した楕円型緩和方程式応力モデルの改良について (乱流の予測とモデリング (2), 一般講演)

恵晶，小尾晋之介

日本流体力学会年会講演論文集 2010, 81 2010

1506 変動速度・圧力同時計測における静圧プローブの形状に関する実験的研究 (OS15-2 先端的熱流体計測法, オーガナイズドセッション)

河田卓也，中吉嗣，深潟康二，小尾晋之介

流体工学部門講演会講演論文集 2010, 445-446 2010

ピエゾフィルムアクチュエータを用いた三次元周期撹乱による乱流混合層の混合促進 (流れの制御 (1), 一般講演)

深潟康二，木戸善幸，中吉嗣，小尾晋之介

日本流体力学会年会講演論文集 2010, 160 2010

The effects of clearance sizes on labyrinth brush seal leakage performance using a Reynolds-averaged Navier-Stokes solver and non-Darcian porous medium model

LI JUN, OBI SHINNOSUKE, FENG ZENGPING

Proceedings of the Institution of Mechanical Engineers Part A-Journal of Power and Energy (Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy) 223 ( A8 ) 953-964 - 964 2009.12

Research paper (scientific journal), Joint Work, Accepted, ISSN 09576509

Effects of clearance sizes on the pressure and leakage characteristics in a shaft labyrinth brush seal were numerically investigated using Reynolds-averaged Navier-Stokes (RANS) and non-Darcian porous medium model solutions. The leakage flow characteristics in the referenced design shaft labyrinth seal of turbomachinery was initially studied using the RANS solution. The numerical results show that the leakage flowrate increases rapidly with increasing clearance between the bristle pack tip and the rotor surface for the shaft labyrinth brush seal. The leakage flow pattern in the referenced labyrinth seal and the redesigned shaft labyrinth brush seal was also illustrated.

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Simultaneous measurement of three velocity components and fluctuating pressure in a turbulent wing-tip vortex

KAWATA TAKUYA, NAKA YOSHITSUGU, FUKAGATA KOJI, OBI SHINNOSUKE

6th International Symposium on Turbulence, Heat and Mass Transfer 2009-September 27-230 2009.09

Research paper (conference, symposium, etc.), Joint Work, Accepted

An attempt is made for simultaneous measurements of velocity and pressure in three-dimensional turbulent flows by means of a miniature pressure probe combined with a triple hot-film anemometer. A turbulent wing-tip vortex is chosen for the test case because of the strong fluctuation of velocity and pressure near its core region. Measurements are undertaken in the near field. The static pressure fluctuation and the velocity-pressure correlation are experimentally investigated. Although they showed distribution that is consistent with those in previous reports, the influence of probe interference needs be substantially reduced.

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Velocity-pressure correlation measurements in complex free shear flows

NAKA YOSHITSUGU, OBI SHINNOSUKE

International Journal of Heat and Fluid Flow (Elsevier) 30 ( 3 ) 411-420 2009.06

Research paper (scientific journal), Joint Work, Accepted

Simultaneous measurements of fluctuating velocity and pressure were performed in various turbulent free shear flows including a turbulent mixing layer and the wing-tip vortex trailing from a NACA0012 half-wing. Two different methods for fluctuating static pressure measurement were considered: a direct method using a miniature Pitot tube and an indirect method where static pressure was calculated from total pressure. The pressure obtained by either of these methods was correlated with the velocity measured by an X-type hot-wire probe. The results from these two techniques agreed with each other in the turbulent mixing layer. In the wing-tip vortex case, however, some discrepancies were found, although overall characteristics of the pressure-related statistics were adequately captured by both methods.

Modification of flow around a circular cylinder using porous media

NAITO HIROSHI, FUKAGATA KOJI, OBI SHINNOSUKE

6th International Symposium on Turbulent Shear Flow Phenomena (6th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2009) 2009-June 1019-1024 - 1024 2009.06

Research paper (conference, symposium, etc.), Joint Work

Flow around a circular cylinder having a porous surface is studied numerically by means of direct numerical simulation (DNS) and large eddy simulation (LES). The flow in the porous media is represented by a spatially-averaged (i.e., macroscopic) model. The parameters of the most effective porous media are found from a two-dimensional parametric test at the Reynolds number, based on the free stream velocity and the diameter of cylinder, of Re = 1000. The lift force fluctuation is notably reduced in the case of thicker porous surface. The DNS of three-dimensional flow at Re = 1000 reveals that the porous surface works to stabilize the shear layer. The LES at a very high Reynolds number (Re = 105) shows that the vortex shedding is completely suppressed by the porous media, which supports the experimental observation by Sueki et al. (2007). Simulations at different Reynolds numbers show that the stabilization effect works better at higher Reynolds numbers.

Drag reduction in channel flow by traveling wave-like surface heating/cooling

MAMORI HIROYA, FUKAGATA KOJI, OBI SHINNOSUKE

6th International Symposium on Turbulent Shear Flow Phenomena (6th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2009) 2009-June 581-586 - 586 2009.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

Reduction of skin-friction drag in a channel flow by traveling wave-like surface heating/cooling is investigated by means of linear analysis and direct numerical simulation. The linear analysis reveals that a downstream traveling wave can reduce the skin-friction drag. Due to non-quadrature between the streamwise and the wall-normal velocity disturbances induced by the buoyancy force, negative Reynolds shear stress is created in the regions near the walls, which contributes to the skin-friction drag reduction. The direct numerical simulation shows that a traveling wave at a high wavenumber slightly reduces the friction drag in a fully developed turbulent channel flow. The velocity fluctuations and the Reynolds shear stress are slightly attenuated by this control. The friction drag increases for larger magnitudes and lower wavenumbers of the traveling waves. Non-zero mean temperature profile is created due to the turbulent heat flux induced by the control.

Simultaneous measurement of velocity and pressure in a wing-tip vortex

NAKA YOSHITSUGU, AZEGAMI SUGURU, KAWATA TAKUYA, FUKAGATA KOJI, OBI SHINNOSUKE

Journal of Fluid Science and Technology (JSME) 4 ( 1 ) 107-115 2009.02

Research paper (scientific journal), Joint Work, Accepted

Simultaneous measurements of fluctuating velocity and pressure have been conducted in the near field of a wing-tip vortex trailing from a NACA0012 half wing. In the
vortex core, the time-averaged streamwise velocity shows a wake-like profile which exhibits a deficit by approximately 25% of free stream velocity. The meandering of the vortex is evident from both velocity and pressure measurements: The power spectral density (PSD) of the transverse velocity fluctuation increases in the lower frequency range, and the distribution of the pressure fluctuation exhibits an elongated shape in the z direction as well as two peaks slightly off from the vortex center. The distribution of the measured velocity-pressure correlation varies significantly near the center of the
vortex especially in downstream locations.

Fast multipole methods on a cluster of GPUs for the meshless simulation of turbulence

YOKOTA R., NARUMI T., SAKAMAKI R., KAMEOKA S., OBI S., YASUOKA K.

Computer Physics Communications (Computer Physics Communications) 180 ( 11 ) 2066-2078 - 2078 2009

Research paper (scientific journal), Joint Work, Accepted, ISSN 00104655

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平行平板間乱流における渦法の検証 (解析・予測・制御乱流の予測とモデリング (1), 一般講演)

横田理央，小尾晋之介

日本流体力学会年会講演論文集 2009, 253 2009

等温度差チャネル流における進行波状吹出し・吸込みを用いた摩擦抵抗低減と伝熱促進の同時制御

東孝祐，守裕也，深潟康二，小尾晋之介

日本伝熱シンポジウム講演論文集第 46 回日本伝熱シンポジウム, 77-77 2009

レイノルズ平均乱流モデルの現状と展望

小尾晋之介

化学工学= Chemical engineering 73 (5), 214-217 2009

Comparing vortex methods and finite difference methods in a homogeneous turbulent shear flow

横田理央，小尾晋之介

International Journal for Numerical Methods in Fluids 63 (7) (International Journal for Numerical Methods in Fluids) 63 ( 7 ) 828 - 846 2009

ISSN 02712091

The vortex method is applied to the calculation of a homogeneous shear turbulence, and compared with a finite difference code using identical calculation conditions. The core spreading method with spatial adaptation is selected as the viscous diffusion scheme of the vortex method. The shear rate is chosen so that it matches the maximum value observed in a fully developed channel flow. The isosurface, anisotropy tensors, and joint probability density functions reflect the ability of the present vortex method to quantitatively reproduce the anisotropic nature of strongly sheared turbulence, both instantaneously and statistically. Copyright © 2009 John Wiley & Sons, Ltd.

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405 L929 線維芽細胞の増殖性・接着性に及ぼす基材表面凹凸形状の影響 (生体・医療材料 II, 生体・医療材料, オーガナイスドセッション 10)

長井篤，斎藤万里雄，宮田昌悟，小茂鳥潤，小尾晋之介

学術講演会講演論文集 58, 65-66 2009

0507 円柱周りのべき乗則流体の流れの数値シミュレーション (OS5-2 非ニュートン流体の流動現象, オーガナイズドセッション)

犬飼翼，内藤弘士，深潟康二，小尾晋之介

流体工学部門講演会講演論文集 2009, 223-224 2009

0229 熱線流速計と小型静圧プローブを用いた変動速度・圧力の同時測定 (OS2-6 乱流の計測・解析・制御, オーガナイズドセッション)

中吉嗣，河田卓也，深潟康二，小尾晋之介

流体工学部門講演会講演論文集 2009, 147-148 2009

0128 プラズマアクチュエータを用いた吹出し・吸込みによる翼端渦の抑制 (OS1-5 噴流, 後流および剥離流れの流動解析と応用, オーガナイズドセッション)

長谷部仁美，中吉嗣，深潟康二，小尾晋之介

流体工学部門講演会講演論文集 2009, 57-58 2009

プラズマアクチュエータによる三次元撹乱を用いた円柱周りの流れの制御 (解析・予測・制御流れの制御 (1), 一般講演)

井上薫，中吉嗣，深潟康二，小尾晋之介

日本流体力学会年会講演論文集 2009, 350 2009

Lagrangian Vortex Methods in Turbulent Channel Flows

Yokota R., Fukagata K., Obi S.

Springer Proceedings in Physics (Springer Proceedings in Physics) 132 2009

ISSN 09308989

In our present study, we compare the turbulent statistics obtained from a vortex method calculation with a finite difference calculation for the turbulent channel flow. The present vortex method is a standard vortex particle method, which uses the core spreading method with spatial adaptation [1] as the diffusion scheme. The Reynolds number was Reb = 5600 and the calculation domain was 3δ × 2δ ×3 δ ×, where δ is the channel half width. The mean velocity profile after one wash-out time is shown in Fig. 1(a), while the mean velocity gradient and Reynolds stress after one wash-out time are shown in Fig. 1(b). The results of the vortex method show an excessive production of Reynolds stress in the viscous layer.

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On the weak-equilibrium condition for derivation of algebraic heat flux model

QIU JIFENG, OBI SHINNOSUKE, TOMAS B. GATSKI

International Journal of Heat and Fluid Flow (Elsevier) 29 ( 6 ) 1628-1637 - 1637 2008.12

Research paper (scientific journal), Joint Work, Accepted, ISSN 0142727X

Analogous to an algebraic Reynolds stress model, the algebraic heat flux model (AHFM) is derived from a
second-moment closure by invoking the weak-equilibrium condition. The present study investigates this condition in detail as it applies to the advection and diffusive-transport terms. For the advection term, the correct form of this condition in non-inertial frames is obtained by means of an invariant Euclidean transformation. The validity of the diffusive-transport condition is examined through an a priori test using a DNS database for rotating turbulent channel flow with heat transfer. It is shown that the weak-equilibrium condition applied to diffusive-transport term tends to fail in the near-wall region. An alternative form is proposed that is based on an asymptotic analysis of the transport equation budget in the near wall region. An evaluation of proposed form shows that it has the potential to improve the predictive ability of an ARSM for flows involving system rotation and/or streamline curvature.

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Simultaneous measurement of velocity and pressure in a wingtip vortex

AZEGAMI SUGURU, KAWADA TAKUYA, NAKA YOSHITSUGU, OBI SHINNOSUKE

7th JSME-KSME Thermal and Fluids Engineering Conference 2008.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Simultaneous measurements of fluctuating velocity and pressure have been conducted in the near field of a wing-tip vortex trailing from a NACA0012 half wing. In the vortex core, time-averaged streamwise velocity shows a wake-like profile which exhibits a deficit by approximately 25% of free stream velocity. The meandering of vortex is evident from both velocity and pressure measurements: The PSD of transverse velocity fluctuation increases in lower frequency range, and the distribution of pressure fluctuation exhibit elongated shape in z-direction and two peaks slightly off from the vortex center. The measured velocity-pressure correlation shows significant gradient near the center of the vortex especially in a downstream location.

The effect of wing tip vortex to force generation of a flapping wing

SURYADI ALEXANDRE, ISHII TAKAYUKI, OBI SHINNOSUKE

7th JSME-KSME Thermal and Fluids Engineering Conference 2008.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Flow visualization and velocity measurements with particle image velocimetry (PIV) have been conducted in the near field of the tip of a sinusoidally flapping plate with the initial condition of fluid at rest. Experiments were conducted at Reynolds number of 1580 and 3160. We visualized the evolution of vortices and performed force calculation based on stereo PIV velocity field data. Three planes near the wing tip were measured with PIV and we found that several features of the flow from PIV measurements are similar with flow visualization.

The pressure-velocity correlation in the turbulent wingtip vortex flow

ISHII TAKAYUKI, SURYADI ALEXANDRE, OBI SHINNOSUKE

7th JSME-KSME Thermal and Fluids Engineering Conference 2008.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

The present study attempts to characterize the fluctuating pressure field in turbulent flow associated with strong streamwise vortex. The instantaneous velocity distribution is measured by a stereoscopic PIV and the corresponding pressure field is obtained as a solution of discrete Poisson equation. The results are presented for the
statistics of turbulence containing the pressure velocity correlation. It is indicated that the distribution of normal components of Reynolds stress are attributable to the magnitude of velocity pressure-gradient correlation terms in the corresponding transport equations.

Numerical simulation of a plane mixing layer with periodic excitation

SHIMADA KOSUKE, FUKAGATA KOJI, OBI SHINNOSUKE

7th JSME-KSME Thermal and Fluids Engineering Conference 2008.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

We perform direct numerical simulation (DNS) of a plane mixing layer under a predetermined control. The inlet velocity is given as the sum of a hyperbolic-tangent base flow and random disturbances. The base flow is periodically excited to mimic the actuation in the experiment. The Reynolds number (Re) based on the velocity difference and the vorticity thickness is 400. The effects of excitation amplitude and frequency are systematically investigated and it is found that the mixing is enhanced for lower frequency, while suppressed for higher frequency. Through the examination of flow statistics, we clarify the mechanisms of mixing enhancement/suppression due to the control input.

Passive control of flow around a circular cylinder using porous media

NAITO HIROSHI, FUKAGATA KOJI, OBI SHINNOSUKE

7th JSME-KSME Thermal and Fluids Engineering Conference 2008.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Passive flow control around circular cylinder using porous media is studied by means of two-dimensional numerical simulation. Brinkman-Navier-Stokes equation is used to simulate flow in the porous media. The simulation is performed at the Reynolds number of Re = 100 and 1000. Both the drag and lift forces are found to be modified due to the presence of porous media. Especially, the fluctuation of lift force is suppressed at Re = 1000 with an intermediate value of porosity. The case of minimum lift force fluctuation is investigated in detail by examining the statistics and flow visualization.

Velocity-pressure correlation measurements in complex free shear flows

NAKA YOSHITSUGU, OBI SHINNOSUKE

7th Int. Symp. Engineering Turbulence Modelling and Measurements (European Research Collaboration on Flow Turbulence and Combustion) 375-380 2008.06

Research paper (conference, symposium, etc.), Single Work, Accepted

A modification of the elliptic relaxation equation to account for pressure transport in RANS modelling

HUI JING and OBI SHINNOSUKE

7th Int. Symp. Engineering Turbulence Modelling and Measurements (European Research Collaboration on Flow Turbulence and Combustion) 95-100 2008.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

Shearless and sheared flow past a circular cylinder: comparative analysis by means of LES

OMORI TAKESHI, JAKIRLIC SUAD, TROPEA CAMERON and OBI SHINNOSUKE

International Journal of Heat and Fluid Flow 29 703-720 2008.06

Research paper (scientific journal), Joint Work

Evaluation of extended weak-equilibrium condition for fully developed rotating channel flow

QIU JIFENG, GATSKI TOMAS, and OBI SHINNOSUKE

Flow, Turbulence and Combustion 80 ( 4 ) 435-454 2008.06

Research paper (scientific journal), Joint Work, Accepted

The weak-equilibrium condition, which is the basis in the development of algebraic Reynolds stress models is assessed in the prediction of fully developed
turbulent channel flow under the influence of system rotation. The budget of the various terms of the exact transport equation for the anisotropy tensor is evaluated
by using a DNS database. Two diffusive transport constraints are evaluated by using the DNS data. The results show that neither of them can hold for the nearwall
region. An asymptotic analysis of the near-wall behavior is performed and an alternative form of the diffusive transport constraint is proposed. The analysis shows that the proposed alternative diffusive transport constraint has the potential to improve the predictive ability of the resultant ARSM.

Evaluation of extended weak-equilibrium conditions for fully developed rotating channel flow

Qiu J.F., Obi S., Gatski T.B.

Flow, Turbulence and Combustion (Flow, Turbulence and Combustion) 80 ( 4 ) 435 - 454 2008.06

ISSN 13866184

The weak-equilibrium condition, which is the basis in the development of algebraic Reynolds stress models is assessed in the prediction of fully developed turbulent channel flow under the influence of system rotation. The budget of the various terms of the exact transport equation for the anisotropy tensor is evaluated by using a DNS database. Two diffusive transport constraints are evaluated by using the DNS data. The results show that neither of them can hold for the near-wall region. An asymptotic analysis of the near-wall behavior is performed and an alternative form of the diffusive transport constraint is proposed. The analysis shows that the proposed alternative diffusive transport constraint has the potential to improve the predictive ability of the resultant ARSM. © 2008 Springer Science+Business Media B.V.

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The study of colliding vortex rings using a special-purpose computer and FMM

SHEEL TARUN KUMAR, YOKOTA RIO, YASUOKA KENJI, and OBI SHINNOSUKE

Transactions of the Japan Society for Computational Engineering and Science 2008 20080003 2008.02

Research paper (scientific journal), Joint Work, Accepted

翼端渦流れにおける速度・圧力相関の測定 (境界層・せん断流・遷移 (3), 一般講演)

中吉嗣，河田卓也，深潟康二，小尾晋之介

日本流体力学会年会講演論文集 2008, 48 2008

周期撹乱を用いた二次元混合層の混合制御の数値シミュレーション (流れの制御 (2), 一般講演)

島田幸輔，深潟康二，小尾晋之介

日本流体力学会年会講演論文集 2008, 331 2008

多孔質体の表面を持つ円柱周りの流れの数値シミュレーション (流れの制御 (4), 一般講演)

内藤弘士，深潟康二，小尾晋之介

日本流体力学会年会講演論文集 2008, 347 2008

専用計算機と FMM を用いた衝突渦輪の渦法解析

シール・タルン・クマー，横田理央，泰岡顕治，小尾晋之介

日本計算工学会論文集 2008, 20080003-20080003 2008

平行平板間流れにおける進行波状体積力による摩擦抵抗低減効果の線形解析 (流れの制御 (2), 一般講演)

守裕也，深潟康二，オプフナージェローム，小尾晋之介

日本流体力学会年会講演論文集 2008, 330 2008

渦法を用いた平行平板間乱流の解析 (乱流の予測とモデリング (1), 一般講演)

横田理央，深潟康二，小尾晋之介

日本流体力学会年会講演論文集 2008, 337 2008

乱流混合層におけるピエゾフィルムアクチュエータを用いた混合促進 (流れの制御 (3), 一般講演)

亀谷幸憲，中吉嗣，深潟康二，小尾晋之介

日本流体力学会年会講演論文集 2008, 341 2008

639 タービンブレードにおけるラビリンスブラシシールのもれ特性に関する数値解析 (OS8. 流体の数値計算手法と数値シミュレーション (4), オーガナイズドセッション)

李軍，小尾晋之介

計算力学講演会講演論文集 2008, 822-823 2008

Turbulent structure and relaminalization of a rotating turbulent channel flow at high rotaton number

Sato S., Obi S.

2007 Proceedings of the ASME/JSME Thermal Engineering Summer Heat Transfer Conference - HT 2007 (2007 Proceedings of the ASME/JSME Thermal Engineering Summer Heat Transfer Conference - HT 2007) 1 211 - 216 2007.12

ISSN 9780791842744

The present study reports on a series of direct numerical simulation of turbulent rotating channel flows at rotation numbers higher than those previously reported. The bulk Reynolds number (Re) was set approximately constant at 5800, while the non-dimensional rotation number Ro was increased up to 5.79. The flow visualization showed that the structure of the enlarged eddies on the pressure side, and the orientation of the structure was inclined towards downstream. The investigation of the budget of Reynolds stress transport equation indicated that the pressure transport of Reynolds stress and re-distribution term were extraordinary large at higher Ro. This led the conventional decomposition of velocity-pressure correlation terms to being not appropriate in this flow. It is suggested that the Reynolds stress modeling should better target the correlation between velocity and pressure gradient, or pressure diffusion and re-distribution terms must be handled with the same efforts, which indeed increases the task of modeling. Copyright © 2007 by ASME.

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Calculation of isotropic turbulence using a pure Lagrangian vortex method

YOKOTA RIO, SHEEL TARUN KUMAR, OBI SHINNOSUKE

Journal of Computational Physics (Journal of Computational Physics) 226 ( 2 ) 1589-1606 - 1606 2007.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 00219991

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Flow instability and disk vibration of shrouded corotating disk sytem

KANAGAI SHUNSUKE, SUZUKI JOE, OBI SHINNOSUKE, MASUDA SHIGEAKI

Trans. ASME, Journal of Fluids Engineering 129 1306-1313 2007.10

Research paper (scientific journal), Joint Work, Accepted

Flow instability and disk vibration of shrouded corotating disk system

Kanagai S., Suzuki J., Obi S., Masuda S.

Journal of Fluids Engineering, Transactions of the ASME (Journal of Fluids Engineering, Transactions of the ASME) 129 ( 10 ) 1306 - 1313 2007.10

ISSN 00982202

This paper focuses on the interaction between the flow unsteadiness and disk vibration of shrouded corotating disk system to identify the nature of the flow-induced vibration of disks in the wide range of rotation speed below critical. Special attention is paid to the role of the vortical flow structure on the disk vibration and vice versa. The water test rig for optical measurement and the air test rig for hot-wire and vibration measurements are employed, both being axisymmetric models of 3.5 in. hard disk drive. Before investigating fluid-solid interaction, the velocity and vorticity fields between disks are examined by employing a particle image velocimetry, in order to check the flow within our own apparatus to have the same characteristics as those commonly accepted. In the course of this preliminary experiment, it is found that "vortical structures" reported in the previous papers based on the flow visualization are actually "vortices" in the sense that it exhibits closed streamlines with concentrated vorticity at its center when seen from an observer rotating with the structure itself. The measurements of out-of-plane displacement of the disk employing different disk materials reveal that disk vibration begins to occur even in low subcritical speed range, and amplitude of nonrepeatable run out (NRRO) can be uniquely correlated by using the ratio between the rotating speed and the critical speed. The power spectral densities of disk vibration showed that the disk vibrates as a free vibration triggered by, but not forced by, the flow unsteadiness even in the high subcritical speed range. The disk vibration has negligible effect on the vortical flow structure suggesting the soundness of the rigid disk assumption employed in the existing CFD. However, RRO has significant influence on the flow unsteadiness even if the disks are carefully manufactured and assembled. Since the RRO is unavoidable in the real disk system, the flat disk assumption should be considered more carefully. Copyright © 2007 by ASME.

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Fast Vortex method calculation using a special-purpose computer

SHEEL TARUN KUMAR, YASUOKA KENJI and OBI SHINNOSUKE

Computers and Fluids (Computers and Fluids) 36 ( 8 ) 1319-1326 - 1326 2007.09

Research paper (scientific journal), Joint Work, Accepted, ISSN 00457930

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Shearless and sheared flow past a circular cylinder: Comparative analysis by means of LES

OMORI TAKESHI, JAKIRLIC SUAD, TROPEA CAMERON, OBI SHINNOSUKE

Proceedings of 5th Int. Symp. Turbulent Shear Flow Phenomena 2007.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Evaluation of diffusion/transport constraints for ARSM in calculation of fully developed rotating channel flow

QIU JIFENG, OBI SHINNOSUKE, GATSKI THOMAS B.

Proceedings of 5th Int. Symp. Turbulent Shear Flow Phenomena 2007.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Pure Lagrangian vortex methods for the simulation of decaying isotropic turbulence

YOKOTA RIO, OBI SHINNOSUKE

Proceedings of 5th Int. Symp. Turbulent Shear Flow Phenomena 2007.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Development of a miniature probe for velocity-pressure correlation measurement

NAKA YOSHITSUGU, OBI SHINNOSUKE, MASUDA SHIGEAKI

Proceedings of 5th Int. Symp. Turbulent Shear Flow Phenomena 2007.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Computational analysis of the shear-induced lift force on a cylindrical particle by means of LES with relevance to particle-laden liquid flow in an upward duct

OMORI TAKESHI, JAKIRLIC SUAD, OBI SHINNOSUKE, TROPEA CAMERON

Proceedings of 6th International Conference on Multiphase Flow 2007.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

Turbulent structure and relaminalization of a rotating turbulent channel flow at high rotation number

SATO SHINICHIRO, OBI SHINNOSUKE

Proceedings of 2007 ASME-JSME Thermal Engineering Summer Heat Transfer Conference (ASME) 2007.07

Research paper (conference, symposium, etc.), Single Work, Accepted

A Validation of Viscous Dissipation Models for Fast Vortex Methods in Simulations of Decaying Turbulence

TOTSUKA YOSHITAKA, OBI SHINNOSUKE

Journal of Fluid Science and Technology (日本機械学会) 2 ( 1 ) 248-257 2007.06

Research paper (scientific journal), Joint Work, Accepted

For realistic turbulent flow simulations, quantitative representation of turbulent flow dynamics is desired.
In the present study, two-dimensional homogeneous isotropic turbulence is simulated by using a grid-free vortex method to focus on the viscous dissipation process.
The results are compared with those of spectral DNS.
Two viscous diffusion models, i.e., a core spreading model and Moving Particle Semi-implicit(MPS) Laplacian model, are compared.
For the former model, merging and insertion of particles are incorporated to ensure uniform distribution of vortex elements.
It is shown that the MPS Laplacian model is superior to the conventional core spreading model in terms of the decay rate of enstrophy and energy spectra.
Furthermore, the computational time is remarkably reduced by using a Fast Multipole Method(FMM), while retaining accuracy.

変動全圧・速度の同時計測による速度・圧力相関の計測 (境界層・せん断流・遷移 (4), 一般講演)

中吉嗣，小尾晋之介

日本流体力学会年会講演論文集 2007, 155 2007

渦法による一様せん断流の解析 (乱流の予測とモデリング (4), 一般講演)

横田理央，小尾晋之介

日本流体力学会年会講演論文集 2007, 195 2007

代数熱流束乱流モデルのユークリッド普遍性について (乱流の予測とモデリング (3), 一般講演)

邱継峰，小尾晋之介

日本流体力学会年会講演論文集 2007, 191 2007

663 回転チャネル乱流の再層流化に関する DNS (OS2-1 乱流のモデリングとシミュレーション)

佐藤眞一郎，小尾晋之介

東海支部総会講演会講演論文集 2007.56, 325-326 2007

662 渦法によるメッシュフリー乱流解析 (OS2-1 乱流のモデリングとシミュレーション)

横田理央，小尾晋之介

東海支部総会講演会講演論文集 2007.56, 323-324 2007

329 乱流混合層における変動全圧・速度の同時計測 (2)(OS3-7 噴流, 後流, せん断流の構造・普遍的特性 (せん断流 1), OS3 噴流, 後流, せん断流の構造・普遍的特性)

中吉嗣，小尾晋之介

流体工学部門講演会講演論文集 2007, _329-1_-_329-4_ 2007

311 翼端渦の乱流速度場計測 (2)(OS3-3 噴流, 後流, せん断流の構造・普遍的特性 (後流 3・噴流 1), OS3 噴流, 後流, せん断流の構造・普遍的特性)

畔上俊，中吉嗣，小尾晋之介

流体工学部門講演会講演論文集 2007, _311-1_-_311-4_ 2007

FPB 処理を施したチタン合金表面における細胞接着性の評価

田口智之，小茂鳥潤，小尾晋之介

JCOM 講演論文集 36, 339-343 2007

The pressure-velocity correlation in oscillatory turbulent flow between a pair of bluff bodies

OBI SHINNOSUKE, TOKAI NORIHIKO

International Journal of Heat and Fluid Flow (Elsevier) 27 ( 5 ) 768-776 - 776 2006.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 0142727X

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Statistics of velocity field in laboratory-simulated downburst

NAGATA TAIICHI, OBI SHINNOSUKE, MASUDA SHIGEAKI

AIAA Journal (AIAA Journal) 44 ( 9 ) 2061-2070 - 2070 2006.09

Research paper (scientific journal), Joint Work, Accepted, ISSN 00011452

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Simultaneous measurements of fluctuating velocity and pressure in a turbulent mixing layer

NAKA YOSHITSUGU, OMORI TAKESHI, OBI SHINNOSUKE, MASUDA SHIGEAKI

International Journal of Heat and Fluid Flow (Elsevier) 27 ( 4 ) 737-746 - 746 2006.08

Research paper (scientific journal), Joint Work, Accepted, ISSN 0142727X

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優れた留学生を確保するには

OBI SHINNOSUKE

留学交流 (日本学生支援機構（編集）) 18 ( 5 ) 2-5 2006.05

Research paper (scientific journal), Single Work

1202 渦法・境界要素法による流体-固体連成解析 (2)(OS12-1 飛ぶもの・泳ぐものとそのメカニズム・流体力学, OS12 飛ぶもの・泳ぐものとそのメカニズム・流体力学)

横田理央，小尾晋之介

流体工学部門講演会講演論文集 2006, _1202-1_-_1202-4_ 2006

AM06-12-011 剥離する軸対称乱流境界層における非定常・局所的逆流の検知 (乱流現象の制御・流れの抵抗低減 (3), 一般講演)

遠藤隆人，益田重明，小尾晋之介

日本流体力学会年会講演論文集 2006, 271 2006

AM06-11-012 自由せん断乱流における速度・圧力相関に関する実験的研究 (境界層とせん断流・遷移 (3), 一般講演)

中吉嗣，小尾晋之介，益田重明

日本流体力学会年会講演論文集 2006, 259 2006

2612 二重円筒間高クヌッセン数クエット流に発生するすべり速度の計測 (S44-2 マイクロ・ナノ流れの実験・計測, S44 マイクロ・ナノフルイディクス)

小尾晋之介，金慧英

年次大会講演論文集 2006.2, 285-286 2006

20306 非平衡自由せん断乱流場における速度・圧力の同時計測 (流れの計測と制御 (1), OS6 流れの計測と制御)

中吉嗣，小尾晋之介，益田重明

日本機械学会関東支部総会講演会講演論文集 2006.12, 153-154 2006

2016 渦法を用いた物体後流の 3 次元解析 (S04-2 FEM/メッシュフリー法/粒子法とその関連技術 (2), S04 FEM/メッシュフリー法/粒子法とその関連技術)

横田理央，小尾晋之介

年次大会講演論文集 2006.1, 31-32 2006

Vortex flow simulation of multiple bluff bodies

YOKOTA, RIO and OBI, SHINNOSUKE

3rd International Conference on Vortex Flows and Vortex Models 191-196 2005.11

Research paper (conference, symposium, etc.), Single Work, Accepted

Acceleration of vortex method calculation using MDGRAPE-2: a special purpose computer

TARUN KUMAR SHEEL, YASUOKA KENJI, OBI SHINNOSUKE

3rd International Conference on Vortex Flows and Vortex Models 137-142 2005.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

Numerical simulation of vortex ring with density difference

ARIZONO TOMOYUKI, MASUDA SHIGEAKI, OBI SHINNOSUKE

3rd International Conference on Vortex Flows and Vortex Models 269-274 2005.11

Research paper (conference, symposium, etc.), Single Work, Accepted

Oscillatory turbulent flow around a pair of square cylinder in tandem

TOKAI NORIHIKO, OBI SHINNOSUKE

Int. Conf. on Jets, Wakes and Separated Flows (The Japan Society of Mechanical Engineers) 527-532 2005.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

国際連携教育と国際センター

OBI SHINNOSUKE

三田評論 2005.10

Research paper (scientific journal), Single Work

Experimental study on velocity-pressure correlation in turbulent mixing layer out of equilibrium state

NAKA YOSHITSUGU, OMORI TAKESHI, OBI SHINNOSUKE, MASUDA SHIGEAKI

4th International Symposium on Turbulent Shear Flow Phenomena (4th International Symposium on Turbulence and Shear Flow Phenomena) 3 1125-1130 - 1130 2005.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

The role of pressure-velocity correlation in oscillatory flow between a pair of bluff bodies

OBI SHINNOSUKE, TOKAI NORIHIKO, SAKAI KEITA

ERCOFTAC International Symposium on Engineering Turbulence Modelling and Measurements 481-490 2005.05

Research paper (conference, symposium, etc.), Joint Work, Accepted

地面に衝突する鉛直重力流の統計的性質

OBI SHINNOSUKE

title 独立行政法人航空宇宙技術研究所特別資料-special publication of National … 24 ( 1 ) 67-79 2005.02

Research paper (scientific journal), Joint Work, Accepted

高速化渦法による減衰乱流シミュレーションの粘性散逸モデル

TOTSUKA YOSHITAKA, OBI SHINNOSUKE

日本機械学会論文集 B 編 71 (701), 23-29 71 ( 701 ) 23-29 2005.01

Research paper (conference, symposium, etc.), Joint Work

Viscous dissipation model for fast vortex method in simulation of decaying turbulence

Totsuka Y., Obi S.

Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B (Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B) 71 ( 701 ) 23 - 29 2005.01

ISSN 03875016

For realistic turbulent flow simulation, quantitative representation of turbulent flow dynamics is desired. In the present study, two-dimensional homogeneous isotropic turbulence is simulated by using grid-free vortex method to focus on the viscous dissipation process. The results are compared with those of spectral DNS. Two viscous diffusion models, i.e., core spreading model and Moving Particle Semi-implicit (MPS) Laplacian model, are compared. For the former model, marge and addition process are incorporated to ensure uniform distribution of vortex elements. It is shown that the MPS Laplacian model is superior to the conventional core spreading model in terms of the decay rate of enstrophy and energy spectra. Computational time is remarkably reduced by using Fast Multipole Method (FMM) while retaining accuracy.

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乱流モデリングにおける DNS の役割

原英統，小尾晋之介，島信行，須賀一彦，河合勇太，辻義之，久木田豊， ...

Fluid dynamics research 37 (3), 203-230 2005

1713 周囲流体と密度差を持つ渦輪の数値解析 (OS17-3 環境と流れ (乱流形成・ダウンバースト等), OS17 環境と流れ, オーガナイズドセッション)

有薗智之，益田重明，小尾晋之介

流体工学部門講演会講演論文集 2005, 255 2005

1703 不安定成層境界層の三次元構造に関する数値解析 (OS17-1 環境と流れ (大気境界層・成層流), OS17 環境と流れ, オーガナイズドセッション)

高柳望，益田重明，小尾晋之介

流体工学部門講演会講演論文集 2005, 245 2005

WS1-5 渦運動と速度-圧力変動相関 (WS1 うず-その本質と特性 (続)-, ワークショップ)

小尾晋之介

流体工学部門講演会講演論文集 2005, 339 2005

The vortex method applied to simulation of homogeneous isotropic turbulence

TOTSUKA YOSHITAKA, OBI SHINNOSUKE

International Conference on Computational Methods 2004.12

Research paper (conference, symposium, etc.), Joint Work, Accepted

Development of Turbulent Impinging Jet on a Rotating Disk

MINAGAWA YUSUKE, OBI SHINNOSUKE

International Journal of Heat and Fluid Flow (International Journal of Heat and Fluid Flow) 25 ( 5 ) 759-766 - 766 2004.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 0142727X

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Effect of disk-shroud spacing on flow induced vibration in corotating disk

YAMAMOTO WAICHI, OBI SHINNOSUKE, MASUDA SHIGEAKI

ASME Information Storage and Processing Systems Conference, 2004 (ASME) 2004.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

PIV による二箱桁間流れの乱流速度場計測

小尾晋之介

土木学会平成 16 年度全国大会講演論文集 CD-ROM 2004

複数の鈍い形状物体周りの渦流れシミュレーション (OS26b 乱流, 反応流, 混相流などの解析モデルと数値手法)

横田理央，外海憲彦，小尾晋之介

計算力学講演会講演論文集 2004.17, 731-732 2004

慶應義塾大学理工学部におけるガスタービン・流体工学関連研究の紹介

川口修，益田重明，小尾晋之介，松尾亜紀子

日本ガスタービン学会誌= Journal of the Gas Turbine Society of Japan 32 (4), 335-337 2004

環境・資源・エネルギー科学の国際教育と国際協力 (特集エネルギーと環境・慶応義塾大学の取り組み)

小尾晋之介

化学経済 51 (11), 70-77 2004

一様流中に直列に置かれた 2 つの鈍い物体周辺の乱流特性 (OS1-2 噴流, せん断流の特性, 噴流, 後流及びせん断流の基礎と応用)

外海憲彦，小尾晋之介

流体工学部門講演会講演論文集 2004, 212 2004

研究だより慶応義塾大学理工学部におけるガスタービン・流体工学関連研究の紹介

川口修，益田重明，小尾晋之介

日本ガスタービン学会誌 32 (4), 335-337 2004

環境・資源・エネルギー科学の国際教育と国際協力

小尾晋之介

化学経済 51 (11), 70-77 2004

Indirect measurement of slip-velocity between solid wall and gas flow at high Knudsen numbers

Obi, S., Kominami, H. and Nakajima, T.

The International Symposium on Micro-Mechanical Engineering 339-343 2003.12

Research paper (conference, symposium, etc.), Joint Work, Accepted

Asymmmetry and unsteadiness of incipient separation of nominally axisymmetric turbulent boundary layer

Masuda S., Okada K., Takagi R., Obi S.

Proceedings of the ASME/JSME Joint Fluids Engineering Conference (Proceedings of the ASME/JSME Joint Fluids Engineering Conference) 2 B 1103 - 1108 2003.12

ISSN 0791836967

Unsteady and asymmetric behavior of separation of nominally axisymmetric and steady turbulent boundary layer in an axisymmetric expansion is investigated. The test diffusers have the total divergence angle from 8 to 50deg and length-to-diameter ratio of 8. Bulk Reynolds number is ranging between 2.5 × 104and 2.4 × 105. The wall static pressure fluctuation increases monotonically with increasing divergence angle up to 25° and then decreases. The wall static pressure exhibits large scale law frequency fluctuations, occurring almost concurrently in the entire passage. Distributions of both mean velocity and reverse flow fraction in a cross-stream plane show axial-asymmetry of the separated flow, suggesting the rapid growth of circumferential non-uniformity upstream. The velocity measurements employing a split film probe to distinguish the flow directions exhibits intermittent flow reversal with higher velocity as compared with forward flow. The conditional average of wall hot film signals reveals the steep decrease at the incipience of flow reversal.

Second-moment turbulence closure in prediction of channel flow with system rotation

Ichikawa, M., Obi, S. and Masuda, S.

International Gasturbine Conference 2003 Tokyo 2003.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

Turbulent Impinging Jet Onto a Co-axial Rotating Disk

Minagawa, Y. and Obi, S.

4th Int. Symp. Turbulence, Heat and Mass transfer 755-762 2003.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Experimental study on velocity-pressure correlation in turbulent mixing layer

Omori, T., Obi, S. and Masuda, S.

4th Int. Symp. Turbulence, Heat and Mass transfer 253-260 2003.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Statistical Characteristics of vertical gravitational flow impinging onto horizontal ground

Nagata, T., Iyama, K., Obi, S. and Masuda, S.

4th Int. Symp. Turbulence, Heat and Mass transfer 829-836 2003.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Asymmetry and unsteadiness of incipient separation of nominally axisymmetric turbulent boundary layer

Masuda, S., Takagi, R., Okada, K. and Obi, S.

4th ASME-JSME Joint Fluids Engineering Conference 2003.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

On the correlation between instantaneous velocity and pressure-gradient in large-scale turbulence

Obi, S.

4th ASME-JSME Joint Fluids Engineering Conference 2003.07

Research paper (conference, symposium, etc.), Single Work, Accepted

Performance prediction for optical wall shear stress sensor using direct numerical simulation of fluid flow

Shirai, K., Tsuru, K. and Obi, S.

4th ASME-JSME Joint Fluids Engineering Conference (Proceedings of the ASME/JSME Joint Fluids Engineering Conference) 1 A 75 - 80 2003.07

Research paper (conference, symposium, etc.), Joint Work, Accepted, ISSN 9780791836965

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Novel measurement method for local wall shear stress in high Reynolds number flows by utilizing Fresnel's biprism

Shirai, K., Tsuru, K. and Obi, S.

3rd Int. Symp. Turbulent Shear Flow Phenomena 483-488 2003.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

Flow induced vibration of shrouded corotating disk systems in subcritical speed range

Kisaki, S., Yamamoto, W., Obi, S. and Masuda, S.

2003 JSME-IIP/ASME-ISPS Joint Conference on Micromechatronics for Information and Precision Equipment 203-204 2003.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

Microscopic observations of clathrate-hydrate films formed at liquid/liquid interfaces. II. Film thickness in steady water flow

Ito, Y., Kamakura, R., Obi, S. and Mori, Y. H.

Chemical Engineering Science (Chemical Engineering Science) 58 ( 1 ) 107-114 - 114 2003.01

Research paper (conference, symposium, etc.), Joint Work, Accepted, ISSN 00092509

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On the role of correlation between instantaneous velocity and pressure-gradient in large-scale turbulence

Obi Shinnosuke

Proceedings of the ASME/JSME Joint Fluids Engineering Conference (Proceedings of the ASME/JSME Joint Fluids Engineering Conference) 1 C 2059 - 2064 2003

ISSN 9780791836965

Turbulent transport of Reynolds stress by triple moment of fluctuating velocity and pressure-velocity correlation are evaluated from a DNS for wake of a rectangular cylinder located in a uniform flow. The turbulent diffusion transport of turbulent kinetic energy hardly correlates with its gradient vector, indicating that the generally accepted gradient diffusion model is inadequate. It is inferred that the separate modeling of the individual Reynolds stress component provides a better possibility for modeling the turbulent transport in this flow, because of the strong departure from the equilibrium state of turbulence. The possibility of the direct modeling of the pressure gradient-velocity correlation is discussed.

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球面波を用いた局所壁面せん断応力測定方法に関する理論的検討

白井克明，小尾晋之介，益田重明

理論応用力学講演会講演論文集第 52 回理論応用力学講演会講演論文集, 324-324 2003

E-123 地面に衝突する鉛直重力流の統計的性質

長田泰一，井山和人，小尾晋之介，益田重明

日本流体力学会年会講演論文集 2003, 150-151 2003

605 水面波を利用した渦輪の発生

深谷友詞，長田泰一，小尾晋之介，益田重明

流体工学部門講演会講演論文集 2003, 81 2003

1208 一様流中におかれた 2 つの鈍い物体周辺の乱流場

酒井圭太，外海憲彦，小尾晋之介

流体工学部門講演会講演論文集 2003, 146 2003

Evaluation of the pressure-velocity correlation in turbulent wake of a rectangular cylinder

Sakai, K., Maeda, T., and Obi, S.

5th JSME-KSME Fluids Engineering Conference 2002.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

乱流モデル（RANS、k-eモデル）

小尾晋之介

フルードバワーシステム 33 ( 7 ) 438-443 2002.11

Research paper (scientific journal), Single Work

Flow instability and elastic vibration of shrouded corotating disk systems

Fukaya, R., Obi, S., Masuda, S. and Tokuyama, M.

Experiments in Fluids (Experiments in Fluids) 33 ( 3 ) 369-373 - 373 2002.09

Research paper (conference, symposium, etc.), Joint Work, Accepted, ISSN 07234864

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Intratracheal instillation of perfluorocarbon rescued mice with primary pulmonary hypoplasia

Mori, K., Kurihara, N., Obi, S., Hayashida, S., Tokieda, K. and Ikeda, K.

Experimental Lung Research (Experimental Lung Research) 28 ( 6 ) 523-533 - 533 2002.08

Research paper (conference, symposium, etc.), Joint Work, Accepted, ISSN 01902148

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Measurement of wall shear stress by extended laser-Doppler method using dual spherical waves

Shirai, K., Obi, S. and Masuda, S.

The 11th Int. Symp. Appl. Laser Tech. Fluid Mechanics 2002.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

平板に衝突する渦輪の挙動(平板に垂直な面内の速度場)

長田　泰一, 小尾晋之介, 益田　重明

日本機械学会論文集 66 ( 667 ) 733-739 2002.03

Research paper (conference, symposium, etc.), Joint Work

The vortex ring impinging onto a flat plate (vertical cross section and the velocity field)

Nagata T., Obi S., Masuda S.

Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B (Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B) 68 ( 667 ) 733 - 739 2002.03

ISSN 03875016

As a part of the laboratory experiment on an isolated microburst, the instantaneous velocity fields of an impulse-driven vortex ring impinging onto a normal wall were investigated. Vortex rings were visualized by filling ethylene glycol smoke. In this paper, as the sequel of the previous paper (Nagata et al., 2000), by employing PIV, the vertical cross-section of the velocity fields was reported. It was shown that the central downward flow as well as the entrainment above the vortex ring agrees qualitatively with numerical simulation of atmospheric microburst (Proctor, 1984). The roles of vortex ring in the velocity field of microburst was discussed. The time evolution of the total circulation in vertical cross section could be fitted to the theoretical equation for that of incompressible viscous vortex.

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Heat transfer in transitional and turbulent boundary layers with system rotation

Yamawaki, D., Obi, S., and Masuda, S.

Int. J. Heat and Fluid Flow (International Journal of Heat and Fluid Flow) 23 ( 2 ) 186-193 - 193 2002.02

Research paper (conference, symposium, etc.), Joint Work, ISSN 0142727X

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平板に衝突する渦輪の挙動: 平板に垂直な面内の速度場 (流体工学, 流体機械)

長田泰一，小尾晋之介，益田重明

日本機械学会論文集 B 編 68 (667), 733-739 2002

周期的外乱によるバックステップ流れの制御

吉岡修哉，小尾晋之介，益田重明

航空宇宙技術研究所特別資料: 第 28 回境界層遷移の解明と制御研究会講演論文集 54 … 2002

地球流体力学入門地球流体力学入門 26, 2000

長田泰一，小尾晋之介，益田重明

日本機械学會論文集. B 編 68 (667), 733-739 2002

乱流モデル (RANS, k-ε モデル)

小尾晋之介

フルードパワーシステム: 日本フルードパワーシステム学会誌: journal of the Japan … 2002

B125 マイクロバーストの実験室モデル: 重力により駆動される渦輪の性質

長田泰一，小尾晋之介，益田重明

日本流体力学会年会講演論文集 2002, 78-79 2002

A313 回転円盤上の衝突噴流内乱流統計量

皆川佑介，小尾晋之介，益田重明

日本流体力学会年会講演論文集 2002, 390-391 2002

A142 角柱背後の瞬時速度-圧力勾配相関

小尾晋之介，前田卓二，酒井圭太

熱工学講演会講演論文集 2002, 29-30 2002

F231 軸対称乱流境界層の剥離挙動

岡田光平，高木玲，益田重明，小尾晋之介

日本流体力学会年会講演論文集 2002, 376-377 2002

RANS モデルの拡張への取り組み

小尾晋之介

東海支部総会講演会講演論文集 2002.51, 385-386 2002

はく離乱流制御に関するスケール則

吉岡修哉，小尾晋之介，益田重明

航空宇宙技術研究所特別資料: 境界層遷移の解明と制御研究会講演論文集第 29 回 … 2002

解説乱流モデル (RANS, K-ε モデル法)

小尾晋之介

フルードパワーシステム= Journal of the Japan Fluid Power System Society: 日本フ … 2002

Analysis of the homogeneous isotropic turbulence by a three dimensional vortex element method

Totsuka, Y., Obi, S.

Int. Conf. Vortex Methods 71-78 2001.09

Research paper (conference, symposium, etc.), Joint Work, Accepted

Turbulence statistics of periodically perturbed separated flow over backward-facing step

Yoshioka, S., Obi, S., and Masuda, S.

Int. J. Heat and Fluid Flow (International Journal of Heat and Fluid Flow) 22 ( 4 ) 393-401 - 401 2001.08

Research paper (conference, symposium, etc.), Joint Work, ISSN 0142727X

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Organized vortex motion in periodically perturbed turbulent separated flow over a backward- facing step

Yoshioka, S., Obi, S., and Masuda, S.

Int. J. Heat and Fluid Flow (International Journal of Heat and Fluid Flow) 22 ( 3 ) 302-307 - 307 2001.06

Research paper (scientific journal), Joint Work, ISSN 0142727X

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The vortex ring impinging onto a ground surface

Nagata, T., Obi, S., and Masuda, S.

2nd Int. Symp. Turbulent Shear Flow Phenomena 283-288 2001.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

DNS study on the measurement of turbulent wall shear stress using surface-mounted hot-film sensor

Kouno, T., Obi, S, and Masuda, S.

2nd Int. Symp. Turbulent Shear Flow Phenomena 141-146 2001.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

鈍い物体伴流の RANS モデリング

小尾晋之介

日本流体力学会年会講演論文集= Proceedings,... meeting of Japan Society of … 2001

円錐ディフューザにおける乱流剥離に伴う壁面静圧変動特性

高木玲，市川正明，益田重明，小尾晋之介

日本流体力学会年会講演論文集= Proceedings,... meeting of Japan Society of … 2001

周期的外乱によるバックステップ後流構造の変化について

吉岡修哉，小尾晋之介，益田重明

日本流体力学会年会講演論文集= Proceedings,... meeting of Japan Society of … 2001

回転積層円盤間の不安定流動と円盤振動

日下博之，小尾晋之介，益田重明

日本流体力学会年会講演論文集= Proceedings,... meeting of Japan Society of … 2001

土木学会論文集= Proceedings of JSCE 677, 205-213, 2001-05-21

沖永佳史，小尾晋之介，真壁利明，冲永佳史，平田信行，日野孝則

土木学会論文集 677, 205-213 2001

日本流体力学会年会講演論文集= Proceedings,... meeting of Japan Society of Fluid Mechanics 2001, 385-386, 2001-07-01

日下博之，小尾晋之介，益田重明

日本流体力学会年会講演論文集 385 (386) 2001

第 16 回生研 NST シンポジウム講演論文集第 16 回生研 NST シンポジウム講演論文集

小尾晋之介

日本流体力学会年会講演論文集 425 (426) 2001

マイクロバーストの実験室モデル

長田泰一，青木功，小尾晋之介，益田重明

大会講演予講集 80, 323 2001

1402 振動を伴うバックステップ乱流の RANS モデル計算 (OS 14-1 非定常性の強い乱流場の CFD)(OS 14 非定常性の強い乱流場の CFD)

小尾晋之介

流体工学部門講演会講演論文集 2001, 194 2001

WS2-2 RANS モデルの限界と可能性 (WS 2 第 9 回 CFD ワークショップ: どこへ向かうのか CFD (その 1))

小尾晋之介

流体工学部門講演会講演論文集 2001, 284 2001

マイクロバーストの実験室モデル

布施信行，長田泰一，小尾晋之介，益田重明

大会講演予講集 79, 388 2001

B322 鈍い物体伴流の RANS モデリング

小尾晋之介

日本流体力学会年会講演論文集 2001, 423-424 2001

Heat transfer experiments in rotating boundary layer flow

Edo, Y.、Obi, S. and Masuda, S.

Int. J. Heat and Fluid Flow (International Journal of Heat and Fluid Flow) 21 ( 6 ) 684 - 692 2000.12

Research paper (scientific journal), Joint Work, ISSN 0142727X

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容器内積層円盤間の流れ

雨宮健一郎、益田重明、小尾晋之介、徳山幹夫、今井郷充

日本機械学会論文集 66 ( 650 ) 2000.10

Research paper (conference, symposium, etc.), Joint Work

Effect of Near-Wall Treatments on the Prediction of Turbulent Separating Flows

Okinaga, Y. and Obi, S.

4th JSME-KSME Thermal Engineering Conference 479-484 2000.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Vortical structures and turbulence statistics of the periodically perturbed separated flow over the backward-facing step

Yoshioka, S.、Obi, S.　and Masuda, S.

4th JSME-KSME Thermal Engineering Conference 457-462 2000.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Flow between shrouded corotating disks

Amemiya K., Masuda S., Obi S., Tokuyama M., Imai S.

ISSN 03875016

As one of the important aerodynamic problems of magnetic disk drives for microcomputers, a flow between shrouded corotating disks and its instability have been investigated. The four-decker circular disk pack is enclosed in a cylindrical container to endure the axial symmetry. Mean and fluctuating velocity fields induced by the disk rotation has been obtained by employing fine scale multi-sensor hot-wire probes. First, the velocity distributions of 2D axisymmetric base flow field are reported. The occurrence of 3D non-axisymmetric flow will then be discussed, where the rotational speed as well as the number of cells will be discussed and compared with the existing data.

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Effect of periodic perturbation on the vortex structure of the turbulent separated flow over the backward-facing step

Yoshioka, S.、Obi, S.　and Masuda, S.

3rd International Symposium on Turbulence, Heat and Mass Transfer 605-612 2000.04

Research paper (conference, symposium, etc.), Joint Work, Accepted

平板に衝突する渦輪の挙動（平板面内の速度場）

（長田泰一、益田重明、小尾晋之介）

日本機械学会論文集B編第66巻 ( 644号 ) 2000.04

Research paper (conference, symposium, etc.), Joint Work

The vortex ring impinging onto a flat plate (horizontal cross section of the velocity field)

Nagata T., Masuda S., Obi S.

ISSN 03875016

As a part of the laboratory experiment on a microburst, the circumferential instability and the associated instantaneous velocity field of a vortex ring impinging onto a normal wall have been investigated. Vortex rings have been generated at the circular orifice by the impulsive motion of the speaker corn and have been visualized by filling ethylene glycol smoke. The instantaneous velocity fields induced by a vortex ring were measured by employing the PIV in which the cross correlation method was used. The wave number of the circumferential instability increases with an increase of the initial Reynolds number. The wave number at the same initial Reynolds number decreases as the distance from the orifice increases. It was shown that the development of induced secondary vortex ring influences the change of velocity vector fields.

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回転境界層内のゲルトラー渦と熱伝達特性

小宮山宏，江戸義博，益田重明，小尾晋之介

年会一般講演 17, 201-202 第66巻 ( 643号 ) 2000.03

Research paper (conference, symposium, etc.), Joint Work

Görtler vortices and their effect on heat transfer in rotating boundary layer

Komiyama H., Edo Y., Masuda S., Obi S.

ISSN 03875016

This paper reports on the influence of Coriolis force on the heat transfer characteristics in rotating laminar boundary layer. The experiments have been conducted for the mean flow velocity U8=4.0m/s and the angular velocity Ω=4.6 rad/s, and the heat flux has been applied uniformly over the plate. Liquid crystal method is applied to measuring the surface temperature distribution. The results indicate that heat transfer has been enhanced on the pressure surface. The velcity measurements show that Coriolis instability induces the counter-rotating longitudinal vortices which argument the heat transfer from the pressure surface. On the other hand, the heat transfer from the suction surface remains unchanged as compared to the no-rotating case, which is due to the Coriolis force that stabilizes the boundary layer. As a consequence, the averaged heat transfer coefficient is higher on the pressure surface than that on the suction surface and the stationary wall by approximately 40%.

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周期的外乱を受けるはく離せん断層における渦構造について

吉岡修哉，小尾晋之介，益田重明

年会一般講演 18, 175-176 第19巻 ( 1号 ) 2000.01

Research paper (scientific journal), Joint Work

電気通信研究所研究実用化報告電気通信研究所研究実用化報告 26-2, 563, 1977

雨宮健一郎，益田重明，小尾晋之介，徳山幹夫，今井郷充

日本機械学会論文集. B 編 66 (00650), 2559-2564 2000

周期的外乱を受けるバックステップ乱流の大規模構造について

吉岡修哉，小尾晋之介，益田重明

航空宇宙技術研究所特別資料 47, 65-66 2000

地面に衝突する渦輪の速度場

長田泰一，小尾晋之介，益田重明

航空宇宙技術研究所特別資料 47, 37-38 2000

容器内積層回転円盤間の流れ

雨宮健一郎，益田重明，小尾晋之介，徳山幹夫，今井郷充

日本機械学会論文集 B 編 66 (650), 2559-2564 2000

平板に衝突する渦輪の挙動: 平板面内の速度場 (< 小特集>: 渦)

長田泰一，益田重明，小尾晋之介

日本機械学会論文集 B 編 66 (644), 990-996 2000

日本機械学会論文集 (B) 日本機械学会論文集 (B) 66-650, 47, 2000

日下博之，小尾晋之介，益田重明

日本機械学会論文集 (B) 66 (650), 47 2000

第 29 回日本伝熱シンポジウム講演論文集第 29 回日本伝熱シンポジウム講演論文集, 694-696, 1992

小宮山宏，江戸義博，益田重明，小尾晋之介

日本機械学会論文集. B 編 66 (00643), 768-773 2000

マイクロバーストの実験シミュレーション

長田泰一，小尾晋之介，益田重明

年会一般講演 19, 199-200 2000

717 PIV 速度データに基づく瞬時圧力場の計測 (オーガナイズドセッション 7 流れの可視化応用解析)

本坊光朗，小尾晋之介，益田重明

日本機械学会関東支部総会講演会講演論文集 2000.6, 183-184 2000

402 周期的外乱を受けるバックステップ流れの大規模構造

吉岡修哉，小尾晋之介，益田重明

流体工学部門講演会講演論文集 2000, 58 2000

3 次元渦法解析における高速化手法に関する検討

戸塚義孝，小尾晋之介

年会一般講演 19, 569-570 2000

1908 周期的外乱によるバックステップ流れの制御

吉岡修哉，小尾晋之介，益田重明

年次大会講演論文集 2000.4, 83-84 2000

WS4-2 はく離乱流に及ぼす周期的外乱の影響

小尾晋之介

流体工学部門講演会講演論文集 2000, 299-302 2000

バックステップ乱流の瞬時圧力分布

小嶋洋太，吉岡修哉，小尾晋之介，益田重明

年会一般講演 19, 341-342 2000

E312 3 次元渦法解析における高速化手法に関する検討

戸塚，小尾晋之介

日本流体力学会年会講演論文集 2000, 569-570 2000

Large scale structure in periodically perturbed turbulent flow over a backward-facing step

吉岡修哉，小尾晋之介，益田重明

航空宇宙技術研究所特別資料 48, 55-56 2000

Momentum transfer in the periodically perturbed turbulent separated flow over the backward-facing step

Yoshioka, S., Obi, S., and Masuda, S.

1st Int. Symp. Turbulent Shear Flow Phenomena 1321-1326 1999.09

Research paper (conference, symposium, etc.), Joint Work, Accepted

Reynolds number effect on the turbulent separating flow in an asymmetric plane diffuser

Obi, S., Nikaido, H., and Masuda, S.

ASME/JSME Fluids Engineering Division Summer Meeting (Proceedings of the 1999 3rd ASME/JSME Joint Fluids Engineering Conference, FEDSM'99, San Francisco, California, USA, 18-23 July 1999 (CD-ROM)) 1999.07

Research paper (conference, symposium, etc.), Joint Work, Accepted, ISSN 0791819612

周期的外乱を受けるバックステップ流の乱流統計量について

吉岡修哉，枡川高久，小尾晋之介，益田重明

日本機械学会論文集 B 編 65 (629), 179-184 65巻 ( 629号 ) 179-184 1999.01

Research paper (conference, symposium, etc.), Joint Work

角柱から放出される渦中の圧力速度相関

本防光朗，小尾晋之介，益田重明

年会一般講演 18, 169-170 1999

回転ゲルトラー流れと熱伝達

益田重明，小尾晋之介，江戸義博

航空宇宙技術研究所特別資料 43, 113-114 1999

第 11 回生研 NST シンポジウム講演論文集第 11 回生研 NST シンポジウム講演論文集 9, 1996

姫木仲秋，小尾晋之介，益田重明，吉岡修哉，枡川高久，小尾晋之助

日本機械学会論文集. B 編 65 (00629), 179-184 1999

代数応力モデルによる二次元非対称ディフューザ内乱流はく離の数値予測

沖永佳史，小尾晋之介

年会一般講演 18, 421-422 1999

マイクロバーストの実験室モデル (平板に衝突する渦輪の速度場)

長田泰一，益田重明，小尾晋之介

大会講演予講集 76, 403 1999

乱流モデル応用研究会の活動について

藤原仁志，小尾晋之介，山本誠，半場藤弘，岡本正芳，秋山実，荒木和博， ...

航空宇宙技術研究所特別資料 44, 281-284 1999

Turbulent statistics of Backward-Facing step flow with periodic perturbations

Yoshioka S., Masukawa T., Obi S., Masuda S.

ISSN 03875016

The experimental study has been conducted on the influence of the periodic perturbation on the separated flow over a backward-facing step. In order to investigate the large-scale eddy motion, which is evolved from the step edge due to the periodic suction and injection, the Particle Image Velocimeter has been introduced. The effect of the perturbation is obvious in reduction of the reattachment length, providing at most the reduction by over 30% against that of the steady flow condition. The investigation on the turbulent transport term in the mean momentum equation reveals the increase in the individual components of Reynolds stress is responsible for the activated momentum transfer across the shear layer, which in turn results in the earlier flow reattachment. The general tendency is in good accordance with other studies in past, though the relative level of the turbulent shear stress is somewhat low. Further investigation on this point is necessary.

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Role of the vortex motion in the periodically perturbed turbulent separated flow over the backward-facing step

Yoshioka, S. Obi, S. and Masuda, S.

4th KSME-JSME Fluids Engineering Conference 585-588 1998.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

周期的外乱を受けるバックステップ流の運動量輸送について

吉岡修哉，小尾晋之介，益田重明

年会一般講演 17, 223-224 1998

単一傾斜型熱線風速計による二次元混合層の乱流計測

小形俊夫，前鶴昭徳，小尾晋之介，益田重明

年会一般講演 17, 183-184 1998

二次元非対称ディフューザ内乱流のはく離予測について

冲永佳史，小尾晋之介

年会一般講演 17, 179-180 1998

2・2 境界層 (2. 非圧縮性流れ)(流体工学機械工学年鑑 (1997 年))

小尾晋之介

日本機械学會論文集. B 編 64 (624), 2368 1998

チャネル乱流の壁面せん断応力統計量に関する実験的研究

小尾晋之介

日本流体力学会誌「ながれ」 17 (2), 74-79 1998

The mechanism of momemtum transfer enhancement in the periodically perturbed turbulent separated flow

Obi, S. Ishibashi, N. Masuda, S.

2nd Int. Symp. Turbulence, Heat and Mass Transfer 835-844 1997.06

Research paper (conference, symposium, etc.), Joint Work

周期的外乱によるディフューザ内乱流はく離流の制御 (制御効果と速度場の変化)

石橋信正、青木謙太、小尾晋之介、益田重明

日本機械学会論文集B編 63巻 ( 605号 ) 1997.01

Research paper (conference, symposium, etc.), Joint Work

Control of turbulent separated flow in a plane diffuser using periodic perturbation (control effects and response of velocity field)

Ishibashi N., Aoki K., Obi S., Masuda S.

ISSN 03875016

The effects of periodic perturbation on turbulent separated flow in a two-dimensional asymmetric diffuser were investigated. Measurements of velocity fields were undertaken using a LDV, and data reduction was conducted on a time-averaged as well as ensemble-averaged manner that made the mean-periodic-turbulent decomposition possible. Effects of imposed perturbation on the velocity field strongly depend on the frequency of the perturbation, and the optimum frequency ranges between 0.01≤St≤0.04, with St being the perturbation frequency normalized by the channel height at the diffuser inlet and the maximum inlet velocity. At the optimum frequency, the effect of perturbation appears as an organized velocity fluctuation along a separated shear flow, resulting in the enhancement of momentum transport, which is the primary effect of imposed perturbation. An increase in the turbulent Reynolds stress component in the recirculation region is also observed, indicating the secondary effect of the organized fluid motion due to periodic perturbation.

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周期的外乱に対するバックステップ流の応答特性

枡川高久，吉岡修哉，斎藤武，小尾晋之介，益田重明

年会一般講演 16, 281-282 1997

周期的外乱によるディフユーザ内乱流はく離流の制御

石橋信正，青木謙太，小尾晋之介，益田重明

日本機械学会論文集 B 編 63 (605), 62-68 1997

二次元混合層における乱流エネルギー収支の測定

小形俊夫，伊藤健二，小尾晋之介，益田重明

年会一般講演 16, 107-108 1997

周期的外乱によるディフユーザ内乱流はく離流の制御制御効果と速度場の変化

石橋信正，青木謙太，小尾晋之介，益田重明

日本機械学会論文集 B 編 63 (605), 62-68 1997

レイノルズ応力の乱流輸送モデル (速度変動三次モーメントの輸送方程式による検討)

原英統、小尾晋之介

日本機械学会論文集B編 62巻 ( 600号 ) 1996.08

Research paper (conference, symposium, etc.), Joint Work

Model of the turbulent transport of Reynolds stress (Study on the transport equation of triple velocity moment)

Hara H., Obi S.

ISSN 03875016

An algebraic model of the turbulent transport of Reynolds stress is proposed, based on an examination of the budget of the transport equation for the third-moment of fluctuating velocity. Combined with a basic version of the second-moment closure, the new model is applied to the calculation of a two-dimensional free mixing layer. The results show a slight modification of the conventional gradient transport model for the turbulent diffusion, and yield a better agreement with experimental results in terms of the amplitude of the third-moment. The inclusion of a simple model for the pressure diffusion term indicates the possibility of further improvement of the turbulent transfer process in free flows.

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二次元混合層における乱流エネルギ収支の測定 (第一報，局所等方性を仮定した乱流エネルギ消散率)

長谷川善行、小尾晋之介、益田重明

日本機械学会論文集B編 62巻 ( 598号 ) 1996.06

Research paper (conference, symposium, etc.), Joint Work

Experimental study on the statistics of wall shear stress in turbulent channel flows

Obi, S., Inoue, K., Furukawa, T., Masuda, S.

Int. J. Heat and Fluid Flow Vol. 17 1996.06

Joint Work

Measurement of turbulent energy budget of the two-dimensional mixing layer (1st report, evaluation of the dissipation rate assuming local isotropy)

Hasegawa Y., Obi S., Masuda S.

ISSN 03875016

Measurement of the turbulent velocity field have been performed in a newly designed low-speed two-dimensional mixing layer facility. Mean and fluctuating velocity in the streamwise direction are measured by an I-type hot-wire anemometer, and the dissipation rate is evaluated from the time derivative of the fluctuating velocity signal based on the Taylor hypothesis and under the assumption of local isotropy of turbulence. The moments of velocity fluctuation up to the third order agree well with previous experiments and DNS, when normalized by the local turbulence velocity scale; the region of self-similarity in terms of the relative turbulence structure is found to be larger than the conventional definition of the global self similarity region where the turbulence velocity scale no longer varies in the streamwise direction. The dissipation rate can also be well correlated with the recent DNS result, when the Taylor micro length scale and local turbulence velocity scale are chosen as the characteristic length and velocity scales, respectively.

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遠心羽根なしディフューザに発生する旋回失速の能動制御

廣瀬則仁，金井剛，小尾晋之介，有賀一郎

日本機械学会論文集 B 編 62 (593), 218-223 62巻 ( 593号 ) 1996.01

Research paper (conference, symposium, etc.), Joint Work

Active control of the rotating stall in a radial vaneless diffuser

Hirose N., Kanai T., Obi S., Ariga I.

ISSN 03875016

An active control method for suppression of the rotating stall in a radial vaneless diffuser is proposed. The activator is driven by the prestall pressure fluctuation detected at the shroud wall of the diffuser. In order to extract the characteristic frequency of the prestall signal, an analogue bandpass filter system as well as a digital signal processor (DSP) system based on an auto-regressive model are adopted and the results obtained using the two systems are compared. The latter realizes a real-time response to the varying frequency of the pressure fluctuation of the prestall. It is confirmed that the critical flow rate is decreased by 12% by the DSP method, yielding a further extension of the operation range of the vaneless diffuser as compared to that of the filter system. The phase angle is found to be an important parameter for the optimum operation of the present control system.

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第 23 回乱流シンポジウム講演論文集第 23 回乱流シンポジウム講演論文集, 254-260, 1991

長谷川善幸，小尾晋之介，益田重明

日本機械学会論文集. B 編 62 (00598), 2187-2193 1996

回転する積層ディスク間流れの乱流構造

小野孝朗，雨宮健一郎，小尾晋之介，益田重明

年会一般講演 15, 133-134 1996

慶應義塾大学におけるガスタービン関連研究

川口修，益田重明，小尾晋之介

日本ガスタービン学会誌 24 (93), 105-107 1996

二次元混合層における乱流エネルギ収支の測定: 第 1 報, 局所等方性を仮定した乱流エネルギ消散率

長谷川善幸，小尾晋之介，益田重明

日本機械学会論文集 B 編 62 (598), 2187-2193 1996

はく離せん断乱流の周期的外乱に対する応答性

姫木仲秋，小尾晋之介，益田重明

年会一般講演 15, 161-162 1996

レイノルズ応力の乱流輸送モデル: 速度変動三次モーメントの輸送方程式による検討

原英統，小尾晋之介

日本機械学会論文集 B 編 62 (600), 2986-2993 1996

主流中の点源攪乱による境界層遷移

浜田慎悟，柴田潔，小尾晋之介，益田重明

年会一般講演 15, 97-98 1996

二次元混合層における乱流エネルギー収支の傾斜型熱線による測定

伊藤健二，小尾晋之介，益田重明

年会一般講演 15, 101-102 1996

慶応義塾大学におけるガスタービン関連研究

川口修，益田重明，小尾晋之介

日本ガスタービン学会誌 24 (93), 105-108 1996

An algebraic model of turbulent diffusion

Obi, S. and Hara, H.

Int. Symp. Mathematical Modelling of Turbulence 1995.12

Joint Work

Experimental and computational study of turbulent heat transfer characteristics in serrated channel flow

Obi, S., Kobayashi, K. P., Bethancourt, A. M., Yoshida, H., Asano, T. and Echigo, R.

Int. J. Heat and Fluid Flow (International Journal of Heat and Fluid Flow) Vol. 16 ( 5 ) 398 - 404 1995.10

Joint Work, ISSN 0142727X

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Experimental study on the statistics of wall shear stress in turbulent channel flows

Obi, S. Inoue, K. Furukawa, T. and Masuda, S.

The Tenth Symposium on Turbulent Shear Flows 5.19-5.24 1995.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

非定常乱流のモデリングに関する研究

小尾晋之介

旭硝子財団助成研究成果報告, p517-523 1995

周期外乱を受ける乱流はく離流の三次元性

石橋信正，小尾晋之介，益田重明

年会一般講演 14, 77-80 1995

二次元混合層における乱流エネルギー収支の測定

長谷川善幸，小尾晋之介，益田重明

年会一般講演 14, 65-68 1995

だ円形方程式に基づく PTV 結果のポストプロセッシング (第 2 報, 非定常流への拡張・誤対応ベクトル除去法・応用実験)

王征成，田中洋一，藤野紳一，長谷川善幸，小尾晋之介，益田重明， ...

計測自動制御学会論文集 31 (3), 399-401 1995

レイノルズ応力の乱流輸送モデル

原英統，小尾晋之介

年会一般講演 14, 231-234 1995

Experimental and computational study on turbulent heat transfer characteristics in the serrated channel flow

Obi, S., Kobayashi, K., Yoshida, H., Asano, T. and Echigo, R.

International Symposium on Turbulence, Heat and Mass Transfer 5.5.1-5.5.6 1994.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Turbulence structure of skewed boundary layer flows in a model radial vaneless diffuser

Tanaka, K., Kanda, M., Obi, S. and Ariga, I.

The third JSME-KSME Fluids Engineering Conference 126-131 1994.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

Application of a multi-angle laser-2-focus velocimeter to unsteady flow measurements in a centrifugal compressor

Sugiyama, A., Obi, S., Maeda, M. and Ariga, I.

7th Int. Symposium on Application of Laser Techniques to Fluid Dynamics 3.3.1-3.3.6 1994.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

Measuring instantaneous local wall shear stress by a laser gradient meter

Inoue, K., Obi, S. and Masuda, S.

The third JSME-KSME Fluids Engineering Conference 141-145 1994.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

Control of turbulent separating and reattaching flow by periodic perturbations

Masuda, S., Obi, S. and Aoki, K.

ASME Fluids Engineering Division Summer Meeting, Turbulence Control (American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED) 193 55-61 - 61 1994.06

Research paper (conference, symposium, etc.), Joint Work, Accepted, ISSN 0791813762

日本流体力学会年会講演論文集= Proceedings,... meeting of Japan Society of Fluid Mechanics 2001, 449-450, 2001-07-01

高木玲，市川正明，益田重明，小尾晋之介

Trans. ASME 116 (4), 842-847 1994

Calculation of the turbulent separating flow in an asymmetric plane diffuser by a second-moment closure model

Obi, S. Masuda, S.

5th Int. Symp. on Computational Fluid Dynamics 381-387 1993.09

Research paper (conference, symposium, etc.), Joint Work

Experimental and computational study of turbulent separating flow in an asymmetric plane diffuser

Obi, S. Aoki, K. and Masuda, S.

Ninth Symp. on Turbulent Shear Flows P305.1-P305.4 1993.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Finite-volume computation of merging parallel channel flows by a second-moment turbulence closure model

Obi, S., Masuda, S.

J. Wind Engineering and Industrial Aerodynamics Vol. 46,47 1993.06

Joint Work

Prediction of strongly swirling flows in quarl expansions with a non-orthogonal finite-volume method and a second-moment turbulence closure

Wennerberg, D. and Obi, S.

2nd Int. Symp. on Engineering Turbulence Modelling and Measurements 197-206 1993.05

Research paper (conference, symposium, etc.), Joint Work, Accepted

Turbulent separation control in a plane asymmetric diffuser by periodic perturbation

Obi, S. Ohizumi, H. Aoki, K. and Masuda, S.

2nd Int. Symp. on Engineering Turbulence Modelling and Measurements 633-642 1993.05

Research paper (conference, symposium, etc.), Joint Work, Accepted

周期的吸込み吹出しによる乱流はく離の制御

大泉博文，小尾晋之介，益田重明

日本機械学会論文集 B 編 59 (557), 123-128 59号 ( 557巻 ) 1993.01

Research paper (conference, symposium, etc.), Joint Work

Control of Turbulent Separation by Periodic Suction and Injection

Ooizumi H., Obi S., Masuda S.

Transactions of the Japan Society of Mechanical Engineers Series B (Transactions of the Japan Society of Mechanical Engineers Series B) 59 ( 557 ) 123 - 128 1993

ISSN 03875016

Effects of periodic perturbation on the turbulent separating flows in a plane two-dimensional asymmetric diffuser have been experimentally investigated. The perturbation was accomplished by alternating injection and suction through a two-dimensional slit located upstream of the expected detachment point. The results indicate that the pressure recovery along the diffuser depends on the frequency as well as the amplitude of the injection/suction flow ; the maximum improvement was achieved at St∼0.03, the Strouhal number St being based on the channel width and channel center velocity at the inlet of the diffuser. The phase-averaged velocity distributions at each phase of the oscillation were evaluated by means of synchronized sampling of the velocity signal employing direction-sensible hot-wire anemometry. A wavy pattern of the instantaneous streamlines, obtained from the velocity profiles, extends throughout the entire region of the diffuser, confirming an enhanced momentum transport due to the organized oscillatory fluid motion. © 1993, The Japan Society of Mechanical Engineers. All rights reserved.

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正方形断面を有する二次元障害物周りの乱流数値解析

小尾晋之介

日本機械学会論文集 B 編 58 (555), 3305-3310 58巻 ( 555号 ) 1992.11

Research paper (conference, symposium, etc.), Joint Work

Finite-volume computation of merging parallel channel flows by a second-moment turbulence closure model

Obi, S. and Masuda, S.

First Int. Symp. on Computational Wind Engineering 225-230 1992.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Numerical Study on the Turbulent Flow around a Two-Dimensional Square-Sectioned Obstacle

Obi S., Perlc M., Scheuerer G.

Transactions of the Japan Society of Mechanical Engineers Series B (Transactions of the Japan Society of Mechanical Engineers Series B) 58 ( 555 ) 3305 - 3310 1992

ISSN 03875016

The assessment of turbulence models including a second-moment closure and the standard k-ε model has been performed for calculating a turbulent separated flow over a surface mounted obstacle. The results indicate more complex characteristics in this problem compared to backward facing step flow which is often used as the test case of turbulence models. Although the required computational effort is much higher than that of the k-ε model, the superior performance of the second-moment closure model is evident in representing the velocity field immediately above the obstacle as well as the pressure variation along the channel. It is indicated that the shortcomings of the k-ε model are attributable to the erroneous behaviour of the production rate of turbulent kinetic energy as calculated according to the eddy viscosity assumption. © 1992, The Japan Society of Mechanical Engineers. All rights reserved.

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A co-located finite-volume method for non-orthogonal grids with a second-moment turbulence closure

Obi, S. and Peric, M.

Proceedings of 4th Int. Symp. on Computational Fluid Dynamics 1991.09

Research paper (conference, symposium, etc.), Joint Work, Accepted

Second-moment calculation procedure for turbulent flows with collocated variable arrangement

Obi, S., Peric, M., Scheuerer, G.

AIAA Journal (AIAA Journal) Vol. 29 ( 4 ) 585 - 590 1991.04

Joint Work, ISSN 00011452

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Finite-volume computation of the flow over a square rib using a second-moment turbulence closure

Obi, S. Peric, M. and Scheuerer, G.

Engineering Turbulence Modelling and Experiments 185-194 1990.09

Research paper (conference, symposium, etc.), Joint Work, Accepted

A finite-volume calculation procedure for turbulent flows with second-order closure and colocated variable arrangement

Obi, S. Peric, M. and Scheuerer, G.

Seventh Symp. on turbulent Shear Flows 17.4.1-17.4.6 1989.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

Finite volume calculation of a high Reynolds number backward facing step flow employing a colocated variable arrangement

Obi, S., Peric, M., Scheuerer, G.

Transport Phenomena in Turbulent Flows, Theory, Experiment and Numerical Simulation 1988.10

Joint Work

Heat transfer characteristics from a flat plate to a gas-solid two-phase flow downstream of a slit injection

Obi, S., Hishida, K., Maeda, M.

Trans ASME, J. Heat Transfer (Journal of Heat Transfer) Vol. 110 ( 3 ) 687 - 694 1988.08

Joint Work, ISSN 00221481

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Experimental and computational investigation of the two-dimensional channel flow over two fences in tandem

Durst, F., Founti, M., Obi, S.

Trans ASME, J. Fluids Engineering, Vol. 110 1988.03

Joint Work

Finite volume calculations of a high Reynolds number backward facing step flow employing a colocated variable arrangement

Obi, S. Peric, M. and Scheuerer, G.

2nd Int. Symp. on Transport Phenomena in Turbulent flows 839-853 1987.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Experimental and computational investigation of the two-dimensional channel flow over two fences in tandem

Durst, F. Founti, M. and Obi, S.

3rd Int. Symposium on Application of Laser Anemometry to Fluid Mechanics 1986.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

Measurements of turbulent recirculating flow in a cylindrical reactor vessel

Obi, S., Hishida, K., Maeda, M., Yokobori, S.

Laser Anemometry in Fluid Mechanics II (Ladoan - Institute Superior Tecnico) 1986.07

Joint Work

大きな再循環流を伴う円筒容器内の乱流特性

小尾晋之介, 菱田公一, 前田昌信, 横堀誠一

日本機械学会論文集B編 51 ( 469 ) 1985.09

Research paper (conference, symposium, etc.), Joint Work

Characteristcs of turbulence in a cylindrical vessel with large scale recirculating flows

Obi S., Hishida K., Maeda M., Yokobori S.

ISSN 03875016

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Measurements of turbulent recirculating flow in a cylindrical reactor vessel

Obi, S. Hishida, K. Maeda, M. and Yokobori, S.

2nd Int. Symposium on Applications of Laser Anemometry to Fluid Mechanics 3.4.1-3.4.6 1984.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

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