Papers - Obi, Shinnosuke

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

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<p>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.</p>

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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

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<p>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.</p>

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

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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

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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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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. Measurements
were conducted with two flapping frequencies to compare the
flow structure. The non-dimensional phase-averaged momentum
flux was similar for both flapping frequencies.

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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

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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

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The fast multipole method (FMM) for periodic boundary conditions is extended to periodic boundary conditions with shear. Using this shear periodic FMM, the pure Lagrangian vortex method is applied to the calculation of a homogeneous shear turbulence, and compared with a finite difference code using identical calculation conditions. The isosurface plots and the anisotropy tensors reflect the ability of the present vortex method to handle strongly sheared turbulence.

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

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<p>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.</p>

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

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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

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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

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<p>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.</p>

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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

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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    27-230 2009.09

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