Explortion of the linear disturbance modes in a wall-bounded turbulent shear flow and bridging the gap between their structures and the turbulent statistics

在本研究中，利用小型扬声器将来自壁面的人工脉冲射流扰动引入平板湍流边界层，并利用热线风速法研究了扰动的发展。速度信号与初始扰动相集平均。这种平均可以提取与人工干扰相关的干扰分量。结果表明，它们的扰动结构不依赖于初始扰动的强度，扰动的幅值与初始扰动的幅值成正比。这是湍流边界层中存在线性扰动的证据。这种线性扰动不仅可以用于湍流射流的分析和预测，还可以用于范围广泛的湍流剪切流的分析和预测。

In this study, artificial pulse jet disturbance from to a wall surface is introduced to a flat-plate turbulent boundary layer using a small speaker and development of the disturbancewas investigated using hot wire anemometry. The velocity signals were ensemble-averaged with phase of the initial disturbance. This averaging enables extraction of disturbance components related to the artificial disturbance. The result shows that their disturbance structure does not depend on strength of the initial disturbance and that amplitude of these disturbances are proportional to that of the initial disturbance. This is evidence that there exist linear disturbances in a turbulent boundary layer. This linear disturbance would be greatly utilized in analysis and prediction of turbulence statistics in not only the turbulent jet but also wide-ranging turbulent shear flows.