一种利用分离区自身能量控制分离的方法

本文用实验方法探讨了非定常扰动对前台阶湍流分离的影响。研究表明采用钢丝为非定常扰源,则不用外加机械能就可达到控制分离的目的。该方法可行的关键在于将钢丝置于分离点后的一个邻域内,在该邻域所特有的自然非稳定涡结构的作用下,钢丝会产生共振,这种共振效应使下泻涡得以强化并形成大尺度的凝聚结构,进而给分离包的低能区补充了能量,使分离包大大缩短。

A METHOD OF CONTROLLING FLUID SEPARATION USING SELF-EXITED UNSTEADYNESS

The active control of separated flows in turbulent boundary layers was achieved experimentally using self-excited oscillations of a steel wire inside the separated zone of a forward facing step. The geo-metric location of steel wire is critical. The present study shows that the control of separation can only be achieved when the steel wire is placed near the point of separation about which the local natural vortex, inter-acts with the steel wire, would resonate it causing strong local vibrations under the inherent frequency of the wire. The shedding frequencies of the vortex will then adjust to that frequency, amplified by it, forming large coherent structures and resulting in dramatic shortenning of the separa-tion bubble.