Details of a Researcher - Obi, Shinnosuke

Presentations -

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回転積層円盤間流れの変動圧力計測

OBI SHINNOSUKE

日本流体力学会年会2012 (高知) ,

2012.09

Oral presentation (general), 日本流体力学会

Investigation of turbulent Couette-like behaviors in a rotating flow

SHIRAI KATSUAKI, SHIGA NOBUO, BUETTNER LARS, OBI SHINNOSUKE, CZARSKE JUERGEN

16th International Symposium on Applications of Laser Techniques to Fluid Mechanics (Lisbon, Portugal) ,

2012.07

Oral presentation (general)

Complex flow inside a hard-disk drive (HDD) was investigated using a simplified 3.5” model to clarify the mechanism causing flow-induced vibration. In contrast to most HDD studies in the past, our model had a non-axisymmetric geometry equipped with a shroud opening and a read/write arm (RWA). The model is designed to serve as a benchmark to study HDD flows both in experiments and in numerical simulations. The secondary flow behavior was likely caused by the shroud opening which wasn’t used in most of the models in the past. In experiment II, the
mean velocity and velocity variance were successfully measured through examination of the flow above and
below the RWA in the space between the rotating disks. The resulting velocity statistics show turbulent
Couette-like flow in the narrow 1 mm space between the disks and the RWA. In addition to the flow
measurements, deflections of components in the model were evaluated during operation, which will provide
precise boundary conditions for future numerical simulations.

Experimental investigation of the flow behavior near the read-and-write arm in a hard disk drive model with shroud opening

SHIRAI KATSUAKI, SHIGA NOBUO, BUETTNER LARS, CZARSKE JUERGEN, OBI SHINNOSUKE

2012 ASME-ISPS /JSME-IIP Joint International Conference on Micromechatronics for Information and Precision Equipment (Santa Clara, CA) ,

2012.06

Oral presentation (general), American Society of Mechanical Engineers

We report a detailed measurement of flow velocities in a simplified, transparent 3.5” hard-disk drive (HDD) model.The simplified geometry of the new model allows systematic flow investigation both in experiments and in numerical simulations. A focus is put on the flow behaviors in the disk-to-disk space with the RWA being inserted. The velocity statistics obtained in the narrow space of 500 μm by means of a novel laser Doppler velocity profile sensor are presented and discussed in this extended abstract.

LES Study of flow between shrouded co-rotating disks

WASHIZU TOMOYA, OBI SHINNOSUKE

9th International ERCOFTAC Symposium on Engineering Turbulence Modeling and Measurements (Thessaloniki, Greece) ,

2012.06

Oral presentation (general), European Research Community of Flow, Turbulence and Combustion

Large eddy simulations of the turbulent flow between shrouded co-rotating disks, representing a simplified model of hard disk drives, are performed.
The computation domain extended a region covering the both sides of a disk, so that the fluctuating pressure field surrounding the disk is simulated.
Besides, the influence of the shroud geometry is investigated by comparing the flat shroud wall and the one with the ribs.
In the case of flat shroud, the fluctuating pressure on the upper- and lower-surface of a disk indicated a strong correlation with the fluid motion travelling across the disk-tip clearance.
In the ribbed shroud case, however, the organized flow structure that is observed in the flat shroud case disappeared, and the fluctuating pressure acting on the surface of the disk is remarkably diminished.

PIV Measurement and force estimation of the flow induced by a heaving elastic plate

KATO KENTARO, OBI SHINNOSUKE

9th International ERCOFTAC Symposium on Engineering Turbulence Modeling and Measurements (Thessaloniki, Greece) ,

2012.06

Oral presentation (general), European Research Community of Flow, Turbulence and Combustion

The vortical uid motion caused by a heaving elastic
plate was experimentally investigated. The thin
plate was oscillated in the direction normal to its plane
in the water at rest. The vortices generated at the tip
of the plate were observed at the mid-span plane and
the velocity eld was measured by means of a particle
image velocimetry (PIV). The measurements were undertaken
at different frequencies of the oscillation relative
to the resonance frequency of the plate. As a result,
phase-averaged momentum ux through these control
surfaces illuminated the effect of relative frequency.

円筒容器内積層回転円盤間乱流のLES

WASHIZU TOMOYA, OBI SHINNOSUKE

第27回生研TSFDシンポジウム (東京) ,

2012.03

Oral presentation (general)

加速する平行平板間流れへの三次元渦法の適用

HIOKI FUMINORI, YOKOTA RIO, OBI SHINNOSUKE

日本流体力学会年会2011 (東京) ,

2011.09

Oral presentation (general), 日本流体力学会

渦度場の時間発展に着目する渦法では、渦度分布を有する渦要素の重ね合わせで渦度場を表現し、渦要素の運動をラグランジュ的に解析する。外部流れのように渦度が領域内の限られた範囲にだけ存在する場合に有利であるが、反面、領域全体が渦度で満たされる内部流れではその検証が十分になされていない。本研究では基礎的な問題として時間とともに発達するチャネル流れを取り上げ、渦度輸送方程式では取り扱うことのできない圧力勾配項を合理的に表現する手法について考察する。

容器内積層回転円盤間乱流のLES

WASHIZU TOMOYA, OBI SHINNOSUKE

日本流体力学会年会2011 (東京) ,

2011.09

Oral presentation (general), 日本流体力学会

過去の実験から得られた知見に基づき，シュ
ラウド壁面が平滑なものと，リブ付きシュラウドの2 つのモデ
ルについて積層回転円盤間に発達する乱流のLES を行い，流体
運動と圧力変動について知見を得ることを目的とする．その際，
1 枚のディスク上下の両面に発達する流れ場の相互干渉を再現
するため，計算領域を3 枚のディスクに囲まれた2 つの隣接す
る領域とした

ヒービング運動する弾性板が誘起する流れ場のPIV 計測

KATO KENTARO, OBI SHINNOSUKE

日本流体力学会年会2011 (東京) ,

2011.09

Oral presentation (general), 日本流体力学会

半円オリフィス乱流のPIV 計測と数値解析

OKUDA SEIYA, LEPEUT CHARLES-HENRI, OBI SHINNOSUKE

日本流体力学会年会2011 (東京) ,

2011.09

Oral presentation (general), 日本流体力学会

Investigation of complex flow behaviors in a hard disk drive model with read-and-write arm and shroud opening

SHIRAI KATSUAKI, SHIGA NOBUO, BÜTTNER LARS, CZARSKE JÜRGEN OBI SHINNOSUKE

Fachtagung “Lasermethoden in der Strömungsmesstechnik” (Ilmenau) ,

2011.09

Oral presentation (general)

Flow inside a hard-disk drive (HDD) is investigated using a simplified 3.5” HDD model with read-and-write arm (RWA) and shroud opening. The model was designed to serve as a benchmark of HDD flow investigation both in experiments and in numerical simulations. In the present study, complex flow behaviors in the narrow disk-to-disk space are focused with the RWA inserted into the space. Especially, the flow behavior near the RWA is of great interest. The velocity statistics are acquired at four different locations using a velocity profile sensor with a spatial resolution of 5 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 velocity profile sensor successfully resolved the velocities between the narrow areas without disturbing the flow.

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

HUI JING, OBI SHINNOSUKE, JAKIRLIC SUAD

7th International Symposium on Turbulence and Shear Flow Phenomena (Ottawa) ,

2011.07

Oral presentation (general)

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
zeta-f model. The presently reformulated model alternatively
solves the transport equations for the ratio of the Reynolds
stress components to turbulent kinetic energy zeta_ij = u_i u_j/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. zeta-f model, is the appearance of the Reynolds stress production rate (representing an exact formulation) in the zeta_ij equations instead of dissipation rate epsilon (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 Re_t = 2003 results in a good
agreement with available DNS database.

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

KAWATA TAKUYA, NAKA YOSHITSUGU, FUKAGATA KOJI, OBI SHINNOSUKE

7th International Symposium on Turbulence and Shear Flow Phenomena (Ottawa) ,

2011.07

Oral presentation (general)

An experimental investigation is conducted into the effect of the shape of a miniature static-pressure probe on the velocity-pressure correlation measurement.
Ten static-pressure probes, with systematically-changed 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.

Velocity measurements of gap flows at a computer hard disk model

SHIRAI KATSUAKI; BUETTNER LARS; CZARSKE JUERGEN, OBI SHINNOSUKE

SENSOR+TEST 2011 (Nuremberg, Germany) ,

2011.06

Oral presentation (general), Organizing Committee

The gap flow in the tip clearance of a hard disk drive model has been investigated with optical measurment techniques. The flow was driven by co-rotating disks inside a cylindrical enclosure in order to simulate a hard disk drive for data storage devices. The main focus of the investigation was the understanding of the complex flow behaviors in the narrow region between the disk tip and the
outer shroud wall, which is supposed to be one of the causes of flow induced vibrations of the disks.

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

KAWATA TAKUYA, NAKA YOSHITSUGU, FUKAGATA KOJI, OBI SHINNOSUKE

第60回理論応用力学講演会 (東京) ,

2011.03

Oral presentation (general), 第60回理論応用力学講演会実行委員会

ヒービング運動する弾性板周りのPIV計測

KATO KENTARO, OBI SHINNOSUKE

第60回理論応用力学講演会 (東京) ,

2011.03

Oral presentation (general), 第60回理論応用力学講演会実行委員会

Pressure estimation on the surface of a sinusoidally oscillating plate in quiescent fluid

SURYADI ALEXANDRE, OBI SHINNOSUKE

The 5th International Conference of Vortex Flows and Vortex Models (Caserta, Italy) ,

2010.11

Oral presentation (general)

This paper presents a method to calculate the pressure field from the far-field to the near-surface of a periodically moving plate. The flow around a simple sinusoidally flapping plate was measured to investigate the dynamics of flow separation and its connection to the production of force of a flapping wing. The flow was measured using stereo PIV at different (out-of-plane) positions relative to the plate to resolve the deformation tensor. Torque acting on the rotation axis was estimated from the velocity field data by solving the pressure equation expressed in the form of Poisson equation. The results were compared with torque measured with strain gauges that were applied on the axis of rotation. The result shows dissimilarity of the pressure field between Re = 1580 and Re = 3160. Torque estimated from the pressure field shows similarity with the torque measured with strain gauges. Although the method shows promising result, it requires further rigorous testing.

Investigation of three-dimensional tip clearance flow inside a hard disk drive model

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

15th Symposium on Application of Laser Techniques to Fluid Mechanics (Lisbon, Portugal) ,

2010.07

Oral presentation (general)

Flow in the tip clearance of a hard disk drive model has been investigated with laser Doppler techniques. The velocity measurements were carried out with two different types of laser Doppler sensors. One was a conventional
laser Doppler velocimetry and the other a novel 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 velocity statistics obtained with both sensors have good agreements in general, but those measured with the conventional velocimetry suffered from a spatial averaging effect.

Surface pressure calculation of flapping wing from three-dimensional velocity field acquired by PIV

SURYADI ALEXANDRE, OBI SHINNOSUKE

14th International Symposium on Flow Visualization (Daegu, Korea) ,

2010.06

Oral presentation (general)

Aerodynamics of a hard disk drive: Measurements of flow velocity, pressure fluctuation and disk vibration

KURASHIMA DAISUKE, NAKA YOSHITSUGU, FUKAGATA KOJI, OBI SHINNOSUKE

8th ERCOFTAC International Symposium on Engineering Turbulence Modelling and Measurements (Marseille) ,

2010.06

Oral presentation (general), ERCOFTAC

The complex feature inside a prototype hard disk drive is investigated both experimentally and computationally. The experiment focuses on both flow dynamics and the disk vibration, where measurements of fluctuating pressure and velocity are undertaken at some representative points. Certain correlation between the disk vibration and the fluctuating pressure in the turbulent flow between disks is found in the spectra of each signal. The computational approach by LES provides information on the whole flow field as complementary to the point measurements. The experimentally observed fluctuation of pressure and velocity are partly due to the disk vibration and its contribution could be estimated by comparing the experiment with the LES results.

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