高超声速流场对自由流扰动波响应及边界层扰动波演化

采用高阶精度有限差分方法直接数值模拟了来流慢声波作用下的钝锥高超声速绕流瞬态流场,分析了自由流扰动波与流场的相互干扰,并应用Fourier频谱分析了边界层扰动波时域和空域演化.结果显示:弓形激波出现连续的“∽”变形,初始扰动被显著放大,边界层内外扰动模态存在明显差别.从空域(沿流线)演化来看,在球头附近低频扰动为主导模态,出了球头区,总扰动模态中的低频和高频成分比例迅速转变,高频模态成分显著地增大.至流场下游,大部分低频分量衰减,或者不再增长,边界层内仅存在特殊频率的不稳定波快速增长.从时域演化来看,比起其他模态,主导模态的发展对上游激励的依赖更大.无论时域还是空域演化,都存在模态竞争现象. 

Response of hypersonic flow field on disturbance wave in free-stream and boundary-layer disturbance wave evolution

To investigate the interaction between hypersonic flow field and disturbance wave in free-stream, a high-order accuracy finite difference method was used to conduct directly numerical simulation of hypersonic transient flow field over a blunt cone under the action of slow acoustic wave. And Fourier frequency spectral analysis was used to study the temporal and spatial evolution of disturbance wave modes in boundary-layer. Results show that consecutive ∽-deformation appeares in bow shock and initial disturbance is enlarged greatly. The disturbance modes outside and inside the boundary-layer differ a lot. For spatial evolution (along the flow direction), the low frequency perturbation modes are dominated within a nose radius; with the disturbance development from upstream to downstream, the high frequency components increase quickly and low frequency components are almost restrained from growth. The ratio between low frequency and high frequency components transforms quickly. In the downstream of the flow field, most of the low-frequency disturbance component are attenuated, or no longer increase; there only exists a special frequency range of unstable wave rapid growth in the boundary-layer. Viewed from the temporal evolution, the dependence of dominant mode on the excitation of upstream is bigger than that of the other mode. Mode competition exists in both the temporal and spatial evolution of disturbance wave modes in boundary-layer.