研究者詳細 - 小尾　晋之介

論文 - 小尾　晋之介

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

小尾晋之介

Experiments in Fluids （Experiments in Fluids） 50 （ 3 ） 573-586 - 586 2011年03月

研究論文（学術雑誌）, 共著, 査読有り, 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. The flow behaviors are investigated for four different conditions with two different gap widths and two different shapes of the shroud walls with and without ribs. The velocity measurements were taken both with conventional laser Doppler velocimetry and using a laser Doppler velocity profile sensor with a spatial resolution in the micrometer range. The circumferential velocity component was measured along the axial and radial directions. The steep gradients of the circumferential mean velocity in both directions were successfully captured with a high spatial resolution, which was achieved by the velocity profile sensor. From the supplementary investigations, the existence of vortex structures in the tip clearance region was confirmed with a dependence on the shroud gap width and the shroud shape. The interactions of the two boundary layers seem to be the source of the complex three-dimensional behaviors of the flow in this region. © 2010 Springer-Verlag.

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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

河田卓也、中吉嗣、深潟康二、小尾晋之介

Flow, Turbulence and Combustion （Springer） 86 （ 3-4 ） 419-437 2011年03月

研究論文（学術雑誌）, 共著

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

横田理央、小尾晋之介

Journal of Flow Science and Technology （Japan Society of Mechanical Engineers） 6 （ 1 ） 14-29 2011年01月

研究論文（学術雑誌）, 共著, 査読有り

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 K., Büttner L., Czarske J., Shiga N., Obi S.

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年

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 Red=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 A., Miyata S., Saito M., Komotori J., Obi S., Naiviba Y., Koyaivia T.

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年

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年

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年

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年

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年

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年

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年

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

小尾晋之介

Experiments in Fluids （Experiments in Fluids） 49 （ 2 ） 447-460 - 460 2010年08月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 07234864

Qualitative and quantitative flow visualizations were performed on a flapping rigid plate to establish a quantitative method for flow observation and evaluation of the force in the near field of a flapping wing. Flow visualization was performed qualitatively with dye visualization and quantitatively with velocity measurements using stereo particle image velocimetry (PIV) on three planes near the tip of the plate along its chord and oriented normally. By ensemble averaging the velocity fields of the same phase angles, they represent a portion of the volume near the tip. Measurements were conducted with two flapping frequencies to compare the flow structure. The second invariant of the deformation tensor visualized the leading edge and mid-chord vortices around the plate appearing due to flow separation behind the plate while other vortical structures were visualized by streamlines. These structures appear to be related to the dynamics of the leading edge vortex. Force analysis by integrating the phase-averaged velocity field within a chosen control volume showed increases in the maxima of the magnitudes of the non-dimensional unsteady force terms on the edge of the plate at the angles after the end of each stroke. The nondimensional phase-averaged momentum flux was similar for both flapping frequencies. © 2010 Springer-Verlag.

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Numerical investigations on leakage performance of the rotating labyrinth honeycomb seal

小尾晋之介

Journal of Engineering for Gas Turbines and Power （Journal of Engineering for Gas Turbines and Power） 132 （ 6 ） 062501 - 1 2010年06月

研究論文（学術雑誌）, 共著, 査読有り, 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. The computed leakage flow rate increased with increasing sealing clearance and pressure ratios. Furthermore, the results show that the studied labyrinth honeycomb seal has the optimum sealing performance in the case of honeycomb cell diameter equals labyrinth step width, and the ratio of the honeycomb cell depth to honeycomb cell diameter is 0.93 under the designed condition. The flow pattern of each case is also illustrated to describe the leakage flow characteristics in labyrinth honeycomb seals. © 2010 by ASME.

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

横田理央、小尾晋之介

International Journal for Numerical Methods in Fluids （John Wiley and Sons Ltd.） 63 （ 7 ） 828-846 2010年05月

研究論文（学術雑誌）, 共著, 査読有り

Acceleration of bluff body calculation using MDGRAPE-2

Sheel T., Obi S.

International Journal of Engineering, Transactions A: Basics （International Journal of Engineering, Transactions A: Basics） 23 （ 2 ） 169 - 176 2010年04月

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

小尾晋之介

Journal of Fluid Science and Technology （JSME） 5 （ 2 ） 156-168 2010年03月

研究論文（学術雑誌）, 共著, 査読有り

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

小尾晋之介

Theoretical and Computational Fluid Dynamics （Theoretical and Computational Fluid Dynamics） 24 （ 1-4 ） 175-179 - 179 2010年03月

研究論文（学術雑誌）, 共著, 査読有り, 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 = 10 6. The simultaneous use of the fast multipole method, Pseudo-particle 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. © 2009 Springer-Verlag.

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Duct water current turbine and extremely low head helical turbine

Phommachanh S., Sutikno P., Shinnosuke O.

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

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年

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年

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