On local boundary-layer receptivity to vortical disturbances in the free stream
On local boundary-layer receptivity to vortical disturbances in the free stream
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DOI：
10.1017/s0022112001006401
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发表时间：
2001-12
影响因子：
3.7
通讯作者：
Xuesong Wu
中科院分区：
文献类型：
--
作者：
Xuesong Wu
根据Dietz（1999）关于自由流中局部粗糙度与涡扰动相互作用引起的边界层感受性的最近实验，本文提出了一个基于三阶渐近理论。渐近的方法使我们能够处理涡扰动与一个相当普遍的垂直分布，并证实了迪茨的结论，对流周期性唤醒在他的实验中，感受性是独立的垂直结构，并可以充分的特点是在边界层的边缘滑移速度。在分布式涡感受性的情况下，产生Tollmien-Schlichting波的主要相互作用发生在上层以及位于边界层外部的所谓边缘层。激发的Tollmien-Schlichting波的初始振幅被确定为O（R−1/8）精度，其中R是全局雷诺数。对于多个粗糙元的情况，导出了一个合适的叠加公式。与Dietz的实验数据进行了全面比较，首次发现了良好的定量一致性，从而解决了该感受性机制的一些不确定性。
Prompted by the recent experiments of Dietz (1999) on boundary-layer receptivity due to a local roughness interacting with a vortical disturbance in the free stream, this paper undertakes to present a second-order asymptotic theory based on the tripledeck formulation. The asymptotic approach allows us to treat vortical perturbations with a fairly general vertical distribution, and confirms Dietz's conclusion that for the convecting periodic wake in his experiments, the receptivity is independent of its vertical structure and can be fully characterized by its slip velocity at the edge of the boundary layer. As in the case of distributed vortical receptivity, dominant interactions that generate Tollmien–Schlichting waves take place in the upper deck as well as in the so-called edge layer centred at the outer reach of the boundary layer. The initial amplitude of the excited Tollmien–Schlichting wave is determined to O(R−1/8) accuracy, where R is the global Reynolds number. An appropriate superposition formula is derived for the case of multiple roughness elements. A comprehensive comparison is made with Dietz's experimental data, and an excellent quantitative agreement has been found for the first time, thereby resolving some uncertainties about this receptivity mechanism.