Details of a Researcher - Obi, Shinnosuke

Papers - Obi, Shinnosuke

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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

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

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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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

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

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

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

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

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

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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