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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.

近年来，自然层流和层流控制翼型的发展在很大程度上依赖于层流-湍流转捩机理。本报告主要研究与边界层转捩的预测和控制密切相关的以下问题：首先，通过直接Navier-Stokes模拟，研究外部扰动内化为T-S波的过程--感受性，了解不稳定波（T-S波）发生的必要条件和耦合系数。还通过实验室和数值实验研究了产生T-S波的非线性感受性过程。结果表明，当频率f远低于中性稳定性曲线的下分支时，频率f的外部扰动可以产生2f的T-S波（以及f的衰减T-S波）。其次，我们研究了亚临界雷诺数下边界层对高强度涡的非线性响应。我们对这种非线性响应的了解对于理解后掠机翼上的附着线污染是至关重要的。结果表明，在前缘对流的高能量发夹涡扰动下，近壁流动相继发展出发夹涡，并在x雷诺数Rx =3.8x10^4以上发生亚临界转捩。我们还研究了脊的壁湍流结构的发展在这个过渡流的效果。