Receptivity of compressible boundary layers over porous surfaces
Receptivity of compressible boundary layers over porous surfaces
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DOI：
10.1103/physrevfluids.8.073903
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发表时间：
2023-06
影响因子：
2.7
通讯作者：
P. Ricco;Ludovico Fossa
中科院分区：
文献类型：
--
作者：
P. Ricco;Ludovico Fossa
用数值方法和渐近方法研究了超音速过渡前边界层在多孔平面和凹面上的流动。多孔壁由薄的等间距圆柱形微腔组成。气流受到对流阵风类型的小幅度自由流涡扰动的扰动。这些外部作用物从前沿附近产生可压缩的Klebanoff模，即沿代数向下游发展的运动学和热学类型的低频扰动。对于展向波长与边界层厚度相当的Klebanoff模，多孔表面对其生长的影响可以忽略不计。当跨向波长大于边界层厚度时，这些扰动被多孔表面有效地衰减。对于一组特定的频率和波长，Klebanoff模通过前沿调节接收机制演化成倾斜的Tollmien-Schlichting波。这些波的波数在多孔表面上只有轻微的改变，而增长速率增加，从而证实了先前的实验结果。基于三层理论的渐近分析证实了这些数值结果。当壁面为凹面时，Klebanoff模的幅值随壁曲率的增大而增大，但在发展初期随壁面孔隙率的增大而减弱。
Supersonic pre-transitional boundary layers flowing over porous flat and concave surfaces are studied using numerical and asymptotic methods. The porous wall is composed of thin equally-spaced cylindrical microcavities. The flow is perturbed by small-amplitude, free-stream vortical disturbances of the convected gust type. From the proximity of the leading edge, these external agents generate the compressible Klebanoff modes, i.e. low-frequency disturbances of the kinematic and thermal kind that grow algebraically downstream. For Klebanoff modes with a spanwise wavelength comparable with the boundary-layer thickness, the porous surface has a negligible effect on their growth. When the spanwise wavelength is instead larger than the boundary-layer thickness, these disturbances are effectively attenuated by the porous surface. For a specified set of frequency and wavelengths, the Klebanoff modes evolve into oblique Tollmien-Schlichting waves through a leading-edge-adjustment receptivity mechanism. The wavenumber of these waves is only slightly modified over the porous surface, while the growth rate increases, thus confirming previous experimental results. An asymptotic analysis based on the triple-deck theory confirms these numerical findings. When the wall is concave, the amplitude of the Klebanoff modes is enhanced by the wall curvature and is attenuated by the wall porosity during the initial development.