Experimental study of the stabilization of Tollmien–Schlichting waves by finite amplitude streaks
Experimental study of the stabilization of Tollmien–Schlichting waves by finite amplitude streaks
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DOI：
10.1063/1.1897377
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发表时间：
2005-05
影响因子：
4.6
通讯作者：
J. Fransson;L. Brandt;A. Talamelli;C. Cossu
中科院分区：
文献类型：
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作者：
J. Fransson;L. Brandt;A. Talamelli;C. Cossu
最近，通过使用时间和空间数值模拟发现了它的稳定最佳条纹中等幅度的最佳条纹，即足够大但不超过拐点不稳定的临界幅度，能够减少Tollmien-Schlichting（TS）的增长（TS），从而完全抑制了其完全抑制。这项研究旨在通过产生稳定和对称的稳定效果，靠近正弦，中等振幅的条纹（类似于自由流速度的12％），通过跨度的圆柱形粗糙度元素来验证这种稳定效果。然后，将三维（3D）条纹基碱流通过板中的跨度插槽产生的二次不稳定性，通过调节的吹气和吸力。在这项研究中，这条条纹在TS波上的稳定作用是明确确认的，并且通过增加粗糙度元素的高度，从而诱导较大的幅度条纹，我们还能够证明对TS波的稳定作用随着条纹振幅而增加。这些结果是第一个确认早期工作中报道的数值预测的结果。完整的横流平面已经在不同的下游位置进行了测量，从而可以进行完整的评估和比较以前的实验工作中使用的不同振幅度量。此外，将理论脉冲响应分析和稳定性计算应用于当前的实验性曲折基流，从而可以对3D调制的TS波分布进行定性比较。
It has recently been found by using temporal and spatial numerical simulations that steady optimal streaks of moderate amplitude, i.e., sufficiently large but not exceeding the critical amplitude for the inflectional instability, are able to reduce the growth of Tollmien-Schlichting (TS) waves up to their complete suppression. This investigation aims at experimentally verifying this stabilizing effect by generating stable and symmetric, close to sinusoidal, streaks of moderate amplitudes (similar to 12% of the free-stream velocity) by means of a spanwise array of cylindrical roughness elements. The three-dimensional (3D) streaky base flow is then subjected to a secondary instability generated through a spanwise slot in the plate by means of regulated blowing and suction. In this study the stabilizing role of the streaks on TS waves is unambiguously confirmed and by increasing the height of the roughness elements, thus inducing larger amplitude streaks, we are also able to show that the stabilizing action on the TS waves increases with the streak amplitude. These results are the first to confirm the numerical predictions reported in earlier works. The full cross-stream plane has been measured at different downstream positions allowing a complete evaluation and comparison of the different amplitude measures used in previous experimental works. Furthermore, theoretical impulse response analysis and stability calculations are applied to the present experimental streaky base flow enabling a qualitative comparison of the 3D modulated TS wave distribution.