- ホーム
- 機能創成セミナー
機能創成セミナー Seminar on Mechanical Science and Bioengineering
第70回 |
2011年11月21日 14:40～16:10
D棟（4階） 共用セミナー室 |
|---|---|
| 「On the growth and decay of patterns in transitional Plane Couette flow」 概要 In plane Couette flow (PCF), the transition to turbulence is characterized by a whole range [R_g,R_t] of Reynolds number where laminar and turbulent flow coexist in the form of alternating oblique bands. R_g is the global stability threshold below which laminar flow prevails in the long time limit, while above R_t turbulence is essentially space-filling. We report on the dynamics of PCF around R_g, studied using direct numerical simulations in systems extended enough for several bands to exist. We consider both how the bands break and decay as R is decreased slightly below R_g and how they grow out of a localized turbulent germ slightly above R_g. Decay involves a two-stage process involving the rupture of a band and next its slow shrinking. Growth is complicated by the fact that two orientations are permitted by the general symmetries of PCF. All these processes are attributed to the transient nature of chaos taking place at the scale of the Minimal Flow Unit in the range of R of interest, which generates a local stochastic process. Band opening during decay as well as nucleation of turbulent buds during growth are proposed to result from large deviations (rare events) depending sensitively on R. |
|
Laboratoire d'Hydrodynamique, Ecole Polytechnique |
|
世話人：河原源太 / 参加者：xxx 名 |
|
第69回 |
2011年11月18日 14:40～16:10
C棟（4階） 共用セミナー室 |
| 「On the transition to/from turbulence in channel flows」 概要 In this talk, we present a series of DNSs conducted in two types of plane channel flows, i.e., plane Poiseuille flow and plane Couette flows, considering the subcritical-transition regime with the use of large aspect-ratio computational domains. Both flows give rise to coexisting laminar and turbulent equilibrium regions in the form of oblique stripes, so-called the turbulent stripe. In addition through the long-term tracking of an isolated turbulent spot, we confirmed that the spot developed into the turbulent stripes in a channel flow at transitional Reynolds numbers. We have also found that, when subjected to stabilizing rotation, the Couette turbulence is locally quenched and exhibits the stripe pattern. In this context, the turbulence stripe can be seen as an intrinsic phenomenon for the transition and the reverse transition in a channel flow. |
|
TU Darmstadt, 東京理科大学 |
|
世話人：河原源太 / 参加者：xxx 名 |
|
第68回 |
2011年11月15日 14:40～16:10
B棟 B204講義室 |
| 「Inertial particles in turbulence: preferential concentration」 概要 Turbulent flows laden with inertial particles occur in many industrial and environmental situations (pollutant dispersion, plankton, engine optimization…). During the last forty years, many properties of these flows have been evidenced, nevertheless, a model equation describing them is still out of reach, particularly regarding the back reaction of the particles on the carrier fluid or regarding the possible collective effects on the particles dynamics. We show experimental results on the strong heterogeneities appearing in the concentration fields and try to identify possible collective effects leading to the existence of clusters that can live for times long compared to the large turbulent scales. We also review the various tools used to evidence and quantify preferential concentration. |
|
ENSTA-ParisTech |
|
世話人：河原源太 / 参加者：xxx 名 |
|
第67回 |
2011年11月11日 14：40～16：10
C棟（4階） 共用セミナー室 |
| 「Laminar-turbulent patterns in plane shear flows」 概要 In this talk we will focus on the large-scale laminar-turbulent patterns found at the onset of transition towards sustained turbulence in subcritical plane shear flows such as plane Couette flow and plane Poiseuille flow. Using high-performance computing we will demonstrate how this onset of turbulence can be delayed to larger values of the Reynolds number in the presence of stabilising forces such as rotation, stratification or Lorenz forces. The fate of these laminar-turbulent patterns in the high-Re case will be discussed. |
|
Laboratoire d'Informatique pour la Mecanique et les Sciences de l'Ingenieur, CNRS |
|
世話人：河原源太 / 参加者：xxx 名 |
|
第66回 |
2011年11月11日 13：00～14：00
A棟 A403講義室 |
| 「陽電子断層法を用いた生体機能の画像化 - 臨床応用に向けた工学的アプローチ -」 概要 陽電子断層法 (positron emission tomography; PET)は、 様々な生体機能を、例えば局所の糖代謝や神経受容体の濃度を 定量的な画像として測定するための医用画像手法である。 しかし、単に投与した放射性薬剤の体内での分布を PETで撮影するだけでは不十分であり、 組織における薬剤の挙動を記述するモデルを推定することで、 初めて生体機能画像が得られる。 そこで本講演では、実際の臨床データを交えつつ、 PET定量画像化に当っての工学的なアプローチを紹介する。 |
|
(独) 放射線医学総合研究所・分子イメージング研究センター |
|
世話人：大城 理 / 参加者：29 名 |
|
第65回 |
2011年11月7日 10：30～12：00
A棟 A403講義室 |
| 「Vortex Flows in the Wake of a Blunt Trailing Edge」 概要 Periodic vortex shedding, also known as Karman vortex shedding, is a common phenomenon that occurs in the wake of a nominally two dimensional blunt trailing edge due to interaction between two separated shears layers from opposite sides. We have employed numerous methods, both active and passive, to suppress this alternate vortex shedding in order to alleviate its detrimental effects such as high form drag, flow induced vibration and noise. In active control method, one of the shear layers at the trailing edge of a blunt based aerofoil was either sucked in or tangentially blown just before the separation. With increasing strength of the suction and blowing, a complete suppression of the vortex shedding could be achieved. The efficacy of the blowing technique was further improved significantly by making it from steady to pulsating. The pulsating blowing was applied in open-loop mode with two control parameters ? blowing strength and pulsating frequency. For the frequency of blowing being twice the unforced vortex shedding frequency and the active phase of the cycle being just 20%, not only a complete suppression of the vortex shedding was achieved but also the wake was found to gain momentum. In passive control method, the spanwise vortex dislocation was introduced by certain geometric cutouts provided at the model trailing edge. The serration shapes were found to introduce strong streamwise vortices in pairs of either co-rotating or contra-rotating by choice. The regular vortex shedding was effectively suppressed resulting in about 34% reduction in the form drag. Moreover, the pairs of contra-rotating vortices were found to generate lift even at zero angle of incidence due to wake vectoring (downwash) effect. |
|
Professor and Head, Aerospace Engineering Department,
Indian Institutes of Technology, Bombay, INDIA |
|
世話人：川野聡恭 / 参加者：xxx 名 |
|
|
|
2011年08月18日 17：30～18：00
A棟 機械科学会議室 |
| 「Electric motorsport: racing vehicle design as a means for innovation in zero emission transport and mobility」 | |
Brunel University London，UK |
|
世話人：和田成生 / 参加者：xxx 名 |
|
第63回 |
2011年06月27日 15：00～16：00
A棟 A403講義室 |
| 「Talbot干渉計の発明と現状」 | |
九州工業大学 |
|
世話人：荒木勉 / 参加者：xxx 名 |
|
第62回 |
2011年06月21日 16：00～
J棟 3Fセミナー室 |
| 「生体信号ゆらぎへの情報論的アプローチとシステム論的アプローチ」 | |
日本大学工学部 |
|
世話人：野村泰伸 / 参加者：xxx 名 |
|
第61回 |
2011年06月07日 16：00～17：00
健康体育研究棟2階セミナー室（豊中キャンパス） |
| 「複数運動スキルの同時学習」 | |
東京大学大学院 教育学研究科身体教育学コース |
|
世話人：野村泰伸 木下 博 / 参加者：xxx 名 |
