壁面振荡对边界层分离的影响

流动分离的控制是当今流体力学领域的一个十分重要的研究课题,本文研究外激发小扰动对基本定常分离流的二阶时均整流效应,结果表明:在合适的St/Re比值下,一个足够大振幅的激发扰动可以推迟甚至抑制分离的发生。

Streaming Effect of Wall Oscillation to Boundary Layer Separation

The flow separation control is an important problem in fluid dynamics.This paper is the first attempt in exploring the streaming effect of unsteady excitation on separation flow. We considered the forcing wave as a small perturbation of the basic steady triple-deck structure near separated point. From the perturbation method we acquired one order perturbated and two order streaming lineared equations, and calculated the timeaveraged streaming effect for different range of St and Re numbers. The velocity distribution of the basic steady flow-field is acquired by the numerical method according to the triple-deck theory. Our main result is that the strong up-welling velocity near separated point can cause a non-negligible streaming because of forcing wave. This streaming caused an appreciable modification of time-averaged velocity profile ( especially time-averaged wall friction ) and thus a shift of separation point. At proper ratio St and Re,a. forcing wave with sufficient amplitude may delay or even suppress the separation. These predictions are in qualitative agreement with varies previous analyses and experiments.