Numerical Study of Local Boundary Layer Receptivity to Freestream Vortical Disturbances
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摘要: 用直接数值模拟的方法研究平板二维边界层对自由流中涡扰动的感受性．在自由流涡扰动与壁面凸起物的相互作用下，在边界层内找到了激发出来的Tollmein-Schlichting(T-S)波，证实了感受性现象及其中波长转变机制的存在．数值模拟得到的T-S波幅值与自由流扰动幅值、凸起高度及矩形凸起物长度的关系，与实验测量所得一致．则由此确定的感受性线性关系式的适用范围亦与实验所得相符．Abstract: Method of direct numerical simulation was used for the investigation of the local receptivity of a 2-D boundary layer of a flat plate to harmonic vortical disturbances in the freestream. Under the interaction of the vortical disturbances in the freestream and the roughness element on the wall, Tollmein-Schlichting (T-S) waves were generated and detected in the boundary layer, thus confirming that the wavelength conversion mechanism and the local receptivity exist. Numerical simulations were performed to obtain the relations between the amplitude of the generated T-S wave and the amplitude of freestream disturbance, the roughness height, and the width of rectangular roughness elements, which agree with those obtained from experiments. Then the range of validity of the linear receptivity formula, which was determined by these relations, also agrees with that determined by experimental results.
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Key words:
- boundary layer /
- receptivity /
- T-S wave /
- wavelength conversion mechanism
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