論文 - 小尾　晋之介

Measurement of the fluctuating pressure on the shroud wall of a hard-disk drive model

Sonoda Y., Sanada K., Obi S.

TURBULENCE HEAT AND MASS TRANSFER 9 (THMT-18) （Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer）  2018-July   689 - 698 2018年

ISSN  2377-2816

　概要を見る

The present study aims at clarifying the turbulent structure developing in a hard disk drive through the measurement of fluctuating pressure on the shroud wall. The measurements have been conducted in two different models, with and without read-write arms, and the results are compared to characterize the effect of the internal structure of turbulent flow on the device. The effect of read-write arms is found to be of primary importance, as it changes the flow structure drastically, with the increasing the arm insertion angle. The most pronounced effect has been found in the gradual change of the characteristic frequency in the power spectrum density of the pressure fluctuation: Both qualitative and quantitative changes are observed.

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Development of a Mechanical Engineering Test Item Bank to promote learning outcomes-based education in Japanese and Indonesian higher education institutions

Jeffrey S. Cross, Estiyanti Ekawati, Satoko Fukahori, Shinnosuke Obi, Yugo Saito, Nathanael P. Tandian, and Farid Triawan

Tuning Journal for Higher Education （University of Deusto）  5 （ 1 ） 41 - 73 2017年11月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  2340-8170

　概要を見る

Following on the 2008-2012 OECD Assessment of Higher Education Learning Outcomes (AHELO) feasibility study of civil engineering, in Japan a mechanical engineering learning outcomes assessment working group was established within the National Institute of Education Research (NIER), which became the Tuning National Center for Japan. The purpose of the project is to develop among engineering faculty members, common understandings of engineering learning outcomes, through the collaborative process of test item development, scoring, and sharing of results. By substantiating abstract level learning outcomes into concrete level learning outcomes that are attainable and assessable, and through measuring and comparing the students’ achievement of learning outcomes, it is anticipated that faculty members will be able to draw practical implications for educational improvement at the program and course levels. The development of a mechanical engineering test item bank began with testscale test implementation in 2016 of 348 first semester master’s students in 9
institutions in Japan, using both multiple choice questions designed to measure the
mastery of basic and engineering sciences, and a constructive response task designed
to measure “how well students can think like an engineer.” The same set of test items
were translated from Japanese into to English and Indonesian, and used to measure
achievement of learning outcomes at Indonesia’s Institut Teknologi Bandung (ITB)
on 37 rising fourth year undergraduate students. This paper highlights how learning
outcomes assessment can effectively facilitate learning outcomes-based education, by
documenting the experience of Japanese and Indonesian mechanical engineering
faculty members engaged in the NIER Test Item Bank project.

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A smooth partition of unity finite element method for vortex particle regularization

Kirchhart M., Obi S.

SIAM Journal on Scientific Computing （SIAM Journal on Scientific Computing）  39 （ 5 ） A2345 - A2364 2017年10月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  10648275

　概要を見る

We present a new class of C∞-smooth finite element spaces on Cartesian grids, based on a partition of unity approach. We use these spaces to construct smooth approximations of particle fields, i.e., finite sums of weighted Dirac deltas. In order to use the spaces on general domains, we propose a fictitious domain formulation, together with a new high-order accurate stabilization. Stability, convergence, and conservation properties of the scheme are established. Numerical experiments confirm the analysis and show that the Cartesian grid-size σ should be taken proportional to the square-root of the particle spacing h, resulting in significant speed-ups in vortex methods.

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A splitting-free vorticity redistribution method

Kirchhart M., Obi S.

Journal of Computational Physics （Journal of Computational Physics）  330   282 - 295 2017年02月

研究論文（学術雑誌）, 共著,  ISSN  0021--9991

　概要を見る

We present a splitting-free variant of the vorticity redistribution method. Spatial consistency 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.

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国際化を推進する学内制度

小尾 晋之介

SFCジャーナル （慶應義塾大学湘南藤沢学会）  17 （ 2 ） 6 - 11 2017年

単著

　概要を見る

大学の国際化を促進するためには留学生の受入れと派遣をスムーズに行えるような学内制度の整備が求められる。EBA コンソーシアムを通じた活動では従来の学期ごとの学生受け入れや派遣の制度では対応できない場面が多々あり、その対応のための「協定学生」を全学的に学則として定めるに至った。一方、学生派遣の充実のためにはカリキュラムとの統合が重要だが、現状では4 学期制の部分的な導入にとどまっている。制度設計においては局所的な最適化だけでなく、コンソーシアムとしての学生の流動性を確保する全体像に常に気を配る必要がある。

Flow control over swept wings using nanosecond-pulse plasma actuator

Kato K., Breitsamter C., Obi S.

International Journal of Heat and Fluid Flow （International Journal of Heat and Fluid Flow）  61, PartA   58 - 67 2016年10月

研究論文（学術雑誌）, 共著,  ISSN  0142-727X

　概要を見る

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. Wind-tunnel tests using a full-span wing model were conducted for various angles of attack α at a Reynolds number Re≡CmU∞/ν=6.0×105, which was based on the effective chord length Cm and freestream velocity U∞. The repetitive frequency of plasma excitation f was also varied from 20 Hz to 1000 Hz. The aerodynamic forces and moments were obtained as a function of α and f by means of a six component balance. The forces and moments were also compared from asymmetric and symmetric actuation configurations point of view: actuations on one side and on both sides of the leading edges. The increase of the time-averaged lift coefficient CL¯ from 0.807 to 0.842 was observed when the symmetric actuation was applied at the reduced frequency of F+≡fCm/U∞≈0.86. The increase of the lift coefficient was strongly correlated with the increase of drag and pitch-up. The frequency dependency of the lift increase was affected by α. Also, the frequency dependency was changed if asymmetric actuation on a leading edge was applied. 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.

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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年

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年

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年

PIV速度データに基づく圧力場の推定方法

小尾 晋之介

ターボ機械 （一般社団法人ターボ機械学会）  43 （ 11 ） 686 - 691 2015年11月

研究論文（学術雑誌）, 単著

Space-time pressure-velocity correlations in a turbulent boundary layer

中 吉嗣、ミシェル・スタニスラス、ジャン マルク・フーコー、セバスチャン・クーデル、ジャンフィリップ・ラヴァル、小尾 晋之介

Journal of Fluid Mechanics （Cambridge University Press）  771   624 - 675 2015年04月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00221120

　概要を見る

The spatio-temporal pressure-velocity correlation in a turbulent boundary layer is investigated so as to understand the link between pressure fluctuations and turbulent coherent structures. A new experimental set-up is developed to measure the pressure fluctuations at the wall and in the field and, simultaneously, the velocity field by stereoscopic particle image velocimetry. The present measurement area covers the whole boundary layer thickness, and the spatial resolution of the measurement is good enough to assess the representative length scales of the flow. The Reynolds number effect is quantified from the data at Re<inf>θ</inf>=7300, 10 000, 18 000. The spatio-temporal three-dimensional structures of the pressure-velocity correlations, R<inf>pu</inf>, R<inf>pv</inf> and R<inf>pw</inf>, are evaluated. The wall pressure fluctuations are closely coupled with coherent structures which occupy a large region of the boundary layer in the wall-normal and spanwise directions and up to 10δ/U<inf>e</inf> in time, where δ and U<inf>e</inf> denote the boundary layer thickness and the free stream velocity. Reynolds number effects are mainly observed on the size and intensity of the pressure-velocity correlations. Conditioning the correlations on the pressure signal sign shows different types of flow phenomena linked to the positive and negative pressure events. For the wall pressure, positive pressure fluctuations appear to be correlated with the leading edge of a large sweeping motion of splatting type followed by a large ejection. The negative pressure fluctuations are linked to a localized ejection upstream, followed by a large sweeping motion downstream. For the pressure fluctuations in the field, in addition to the structures observed with the wall pressure, the pressure-velocity correlations exhibit a significant correlation in a region very extended in time. Such long structures appear to be independent of the one observed at the wall and to grow significantly in time with the Reynolds number when scaling with external variables. When conditioned by the pressure sign, clear ejection and sweeping motions are observed with associated streamwise vortical structures at a scale of the order of 0.2δ. These structures can be linked to the large-scale motion and very-large-scale motion previously observed by different authors and seem to organize in a scheme analogous to the near-wall cycle, but at a much larger scale.

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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年

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年

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年

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年

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年

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年

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年

ISSN  26425629

　概要を見る

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.

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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年

ISSN  26425629

　概要を見る

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.

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Flow separation control over a Gö 387 airfoil by nanosecond pulse-periodic discharge

加藤 賢太郎，Christian Breitsamter, 小尾 晋之介

Experiments in Fluids （Experiments in Fluids）  55 （ 8 ） 1795 2014年08月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  07234864

　概要を見る

Airfoil flow 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. The results show two different manners of the lift increment depending on the angle of attack. At the pre-stall and stall angle, the flow is steady and the lift increment does not depend on the frequency. A strong hysteresis effect is also observed, i.e., once the lift increases due to the plasma actuation, it is still increased even after the actuation stops. At the post-stall angle, the flow is unsteady and the lift increment becomes significant with actuation at frequencies related to inherent flow instabilities for the shear layer and wake, which are determined by the spectrum analysis based on hot-wire measurements. At the preference frequency ranges, there is a certain voltage amplitude depending on the angle of attack, at which the extended plasma layer results in an optimum increase of lift. © 2014 Springer-Verlag Berlin Heidelberg.

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