可压缩平板边界层的二次亚谐不稳定性

Secondary Subharmonic Instability of Compressible Boundary Layer on Flat Plate

用二次稳定性理论研究可压缩平板边界层中三维扰动的产生及其非线性演化过程,揭示可压缩边界层转捩的内在机制.结果表明,可压缩边界层在较宽的波数带内存在亚谐不稳定性,其特性与不可压缩边界层相似;二次亚谐波在很宽频率和雷诺数范围内不稳定,其增长率和幅值放大因子都远大于初始波,二次亚谐共振是可压缩边界层转捩的内在机制.

The process of emerging and evolution of 3D disturbances in a compressible boundary over an insulated flat plat are investigated basing on the secondary instability theory and the transition mechanism is revealed. It is found that the secondary subharmonic wave of the compressible boundary layer share a lot of feature with the incompressible case.The subharmonic instability can be found in a wide extent of the frequencies and Reynolds numbers and the growth rates and amplification factors of amplitude are much higher than that of the primary wave. The secondary subharmonic resonance may be an intrinsic transition mechanism of compressible boundary layer.