周期性扰动在平板湍流边界层传播的实验研究

Research on Propagation and Decay Characteristics of Periodic Disturbance along Longitudinal Direction in a Turbulent Boundary Layer

对不同频率的扰动波在湍流边界层内沿流向的传播进行了实验研究,研究发现,内层的周期扰动使边界层外层产生了扰动波响应,近壁区域的周期扰动在外区引起的扰动波响应振幅远大于内区,边界层内层猝发与边界层外层流动状态之间具有感受性的联系,内层猝发的生成与边界层外层流动状况密切相关。湍流是一个稳定的状态,湍流边界层不存在整体失稳,各种频率的扰动波沿流向的幅值总体上都是衰减的,衰减趋势越来越弱。但扰动波波幅沿流向并不总是单调减小的,有些时候出现局部的波幅增长。

In this paper,the disturbance waves of different frequencies in the turbulent boundary layer along the flow of communication are studied.From the experimental investigation,it is found that the periodic disturbance wave introduced in the near wall regions can cause responding waves in the outer region.The responding wave amplitude in the outer region is much larger than that of the disturbing wave in the near wall region.The coherent structure burst in the near wall region is related receptively to the flow state in the outer region.The occurrence of burst in the near wall region is tied up with the flow state in the outer region.The turbulence is a stable state and there is not global instability in turbulent boundary layer.The global evolution tendency of the disturbing wave with all frequencies is generally damping along the longitudinal direction while the decaying tendency becomes weaker and weaker.But the disturbing wave amplitude does not always decrease monotonously in the downstream direction,although in some cases there is a local momentary increase in particular vertical positions.