Papers - Obi, Shinnosuke

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

　View Summary

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.

• Access to Document (DOI)

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

　View Summary

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

　View Summary

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.

• Access to Document (DOI)

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

　View Summary

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.

• Access to Document (DOI)

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

　View Summary

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.

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

　View Summary

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.

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

　View Summary

Airfoil fow separation control using plasma actuator driven by repetitive nanosecond pulse voltage was experimentally investigated. The pressure distribution on an airfoil
surface was measured by means of a liquid manometer, which is free from electromagnetic interference of the plasma. By integrating the pressure distribution, the lift coefficient was computed and the effects of the input voltage amplitude and repetitive frequency were evaluated.

• Access to Document (DOI)

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

　View Summary

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

• Access to Document (DOI)

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

　View Summary

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.

• Access to Document (DOI)

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

　View Summary

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.

• Access to Document (DOI)