Basic Studies on the Laminar Control of Wing

机翼层流控制的基础研究

基本信息

批准号：
03650054
负责人：
ASAI Masahito
金额：
$ 1.09万
依托单位：
Tokyo Metropolitan Institute of Technology (1992)Osaka Prefecture University (1991)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03650054/
关键词：
Boundary Layer Transition Turbulence Structure Laminar Flow Control Flow Instability Receptivity T-S waves Riblets 後退翼ヘアピン渦

项目摘要

The recent development of the NFL (natural laminar flow) and LFC (laminar flow control)airfoils for the reduction of friction drag heavily relies on our knowledge of the mechanism of laminar-turbulent transition. In this report, examined are the following problems closely related to the prediction and control of boundary layer transition.First, the receptivity, the process by which external disturbances are internalized as T-S waves, is investigated through direct Navier-Stokes simulations to understand the necessary condition for the occurrence of instability waves(T-S waves) and the coupling coefficient. A nonlinear receptivity process generating T-S waves is also examined through laboratory and numerical experiments. The results show that the external disturbance of frequency f can generate T-S wave of 2f (as well as decayed T-S wave of f) if the frequency f is much below the lower branch of the neutral stability curve.Second, we examined nonlinear response of boundary layer to high-intensity vortices at subcritical Reynolds numbers experimentally and numerically. Our knowledge of such nonlinear response is crucial for understanding the attachment-line contamination on a swept wing. The results show that when highly disturbed by energetic hairpin eddies convecting from the leading edge, the near wall flow develops hairpin eddies in succession to lead to the subcritical transition beyond the x-Reynolds number R_x=3.8x10^4. We also examined the effect of riblets on the development of wall turbulence structure in this transitional flow.

NFL（天然层流流）和LFC（层流控制）的最新发展使摩擦拖动的减少重大抗体取决于我们对层流溃疡过渡机制的了解。在本报告中，检查的是以下与边界层过渡的预测和控制密切相关的问题。首先，通过直接的Navier-Stokes模拟研究了接受外部干扰作为T-S波内部化的过程，以了解出现不稳定性波（T-S WAVE（T-S WAVES）的必要条件）和耦合系数。还通过实验室和数值实验检查了非线性接受过程产生T-S波。结果表明，频率F的外部干扰可以产生2F的T-S波（以及F的T-S波），如果频率F低于中性稳定性曲线的下部分支。我们对这种非线性响应的了解对于理解扫掠的机翼上的依恋线污染至关重要。结果表明，当受到前沿的对流的高度打扰，近壁流程会依次发展发夹涡流，从而导致X-Reynolds数字r_x = 3.8x10^4的亚临界过渡。我们还研究了开裂物对这种过渡流中壁湍流结构发展的影响。