Studies on By-Pass Transition of Boundary Layr

边界层旁路转变研究

• 批准号: 08651090
• 负责人: ASAI Masahito
• 金额: $ 1.41万
• 依托单位: Tokyo Metropolitan Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08651090/
• 关键词: Fluid Mechanics; Boundary Layr; Laminar-Turbulent Transition; Turbulent Contamination; Hairpin Eddies; Critical Reynolds Number; 乱流; 境界層

In the present study, the so-called by-pass boundary-layr transition caused by high-intensity disturbances is examined experimentally. Our knowledge of the boundary-layr response to such high-intensity disturbances is crucial, for instance, for understanding the attachment-line contamination on a swept wing. In addition, it is expected that the results give much information on the mechanism of wall turbulence generation and the related critical flow condition.The whole experiment is carried out in a wind tunnel with open jet type. A boundary-layr plate is set in the open test section. Well-controlled hairpin eddies is introduced in Blasius boundary layr at subcritical Reynolds numbers (for linear instability) through a small wall orifice. The results obtained are summarized below.Local turbulent patch created by the orifice-generated hairpin vortices can develop only at Reynolds numbers above R_<rheta>=130 (based on the momentum thickness). In such low-Reynolds number transition, the l … More ateral growth of turbulent patch is very weak, i.e., the lateral spreading angle is less than 2 deg. With increasing the Reynolds number, the lateral spreading angle is rapidly increased towards the typical value (10 deg) at high Reynolds numbers. The dependency of the lateral spreading angle of turbulent patch on R_<rheta> is clearly demonstrated in the present experiment. It is also worth noting that the growth of turbulent patch is highly dependent on the intensity of initial hairpin vortices in this subcritical boundary-layr transition.A key event observed is found to be successive growth of wall shear layrs (lifted up on low-speed streaks) with streamwise vortices into hairpin vortices, which is almost the same as the near-wall phenomena observed in the late stage of the ribbon-induced transition in plane Poiseille flow. Below the critical station (R_<rheta>=130), even if highly disturbed and once the wall streaks with streamwise vortices are created, they eventually decay downstream. Less

在本研究中，通过实验检验了由高强度扰动引起的所谓旁路边界层转变。例如，我们对边界层对这种高强度扰动的响应的了解对于理解后掠翼上的附着线污染至关重要。此外，期望该结果能够提供有关壁面湍流产生机制和相关临界流动条件的更多信息。整个实验在开放射流式风洞中进行。在开放试验段设置边界层板。通过小壁孔在亚临界雷诺数（线性不稳定性）的 Blasius 边界层中引入良好控制的发夹涡流。所获得的结果总结如下。 由孔口产生的发夹涡产生的局部湍流斑块只能在雷诺数高于 R_<rheta>=130（基于动量厚度）时形成。在这种低雷诺数转变中，湍流斑块的横向扩展非常弱，即横向扩展角小于2°。随着雷诺数的增加，横向扩展角迅速增加到高雷诺数下的典型值（10 度）。本实验清楚地证明了湍流斑块横向扩展角对 R_<rheta> 的依赖性。还值得注意的是，湍流斑块的增长高度依赖于这种亚临界边界层转变中初始发夹涡的强度。观察到的一个关键事件是壁剪切层（在低速条纹上上升）的连续增长，流向涡变成发夹涡，这与在平面带引起的转变后期观察到的近壁现象几乎相同 泊瓦叶流。在临界站 (R_<rheta>=130) 以下，即使受到高度干扰，并且一旦产生具有流向涡流的壁条纹，它们最终会在下游衰减。较少的

项目成果

Masahito Asai: "Three-dimensional growth of Tollmien-Schlichting waves excited at two frequencies." Fluid Dynamics Research. 22-4. 215-230 (1998)

Masahito Asai：“在两个频率下激发的 Tollmien-Schlichting 波的三维增长。”

M.Asai: "Development of Wall Turbulence Structure in Transitional Flows" Theoretical and Applied Mechanics 1996,Elsevier. 121-138 (1997)

M.Asai：“过渡流中壁湍流结构的发展”理论与应用力学1996，爱思唯尔。

Masahito Asai: "Lateral Turbulent Contamination in Subcritical Boundary-Layer Transition" Memoirs of Tokyo Metropolitan Institute of Technology. 10. 109-115 (1996)

Masahito Asai：《亚临界边界层转变中的横向湍流污染》东京都工业大学回忆录。

Masahito Asai: "Development of wall turbulence structure in transitional flows." Theoretical and Applied Mechanics (eds.T.Tatsumi, E.Watanabe & T.Kambe), Elsevier. 121-138 (1997)

Masahito Asai：“过渡流中壁面湍流结构的发展。”

M.Asai: "Development of Wall Turbulence Structure in Transitional Flows" ICTAM Kyoto 1996, Elsevier. (1997)

M.Asai：“过渡流中壁湍流结构的发展”ICTAM 京都 1996 年，爱思唯尔。