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在采用直接数值模拟(DNS)方法计算得到来流马赫数为4.5的带局部凸起的可压缩平板边界层基本流的基础上,基于线性稳定性理论(LST)进行稳定性分析,通过求解扰动方程研究了不同频率的扰动波与不同高度的局部凸起的相互作用,定义了穿透系数来研究局部凸起对流动稳定性的影响.研究结果表明:当局部凸起高度小于0.2个边界层厚度时局部凸起对来流的影响是局部的;局部凸起使频率小于最不稳定波频率的扰动波更不稳定,对频率大于最不稳定波频率的扰动波有稳定作用,其中最不稳定波频率是指局部凸起中心位置处平板边界层中第2模态最不稳定波的频率;穿透系数定量刻画了局部凸起对稳定性的影响,高度为0.2个边界层厚度的局部凸起引起e-N方法中N值的修正量达到0.8,接近转捩位置处N值的10%,在转捩预测中必须考虑.
Based on the principle of linear stability theory (LST), the stability of compressible slab boundary layer with local Mach number 4.5 was calculated by direct numerical simulation (DNS) The influence of local bumps on the flow stability is studied by using the equations to study the interaction between disturbance waves of different frequencies and local bumps with different heights. The results show that when the local bump height is less than 0.2 boundary layers The influence of local bulge on the incoming flow is local when the thickness is local. The local bulge stabilizes the disturbance wave whose frequency is less than the most unstable one and stabilizes the disturbance wave whose frequency is greater than the most unstable one. Stabilized wave frequency refers to the frequency of the second modest unstable wave in the slab boundary layer at the center of the local bulge; the penetration coefficient quantitatively depicts the effect of local bulge on the stability, and the height is 0.2 part of the boundary layer thickness The protrusion causes the correction of the N value in the eN method to reach 0.8, close to 10% of the N value at the transitional position, which must be considered in the transition prediction.