Experimental analysis of unsteady shock formation from interactions with turbulent features in a flat plate turbulent boundary layer

在高速工程应用中，激波-边界层相互作用（SWBLI）是指边界层与外超声速流动之间存在紧密耦合。SWBLI的一个显著特征是一个围绕平均位置振荡的非定常激波锋。冲击振荡会导致表面压力波动水平升高，当这种波动强度足够大时，可能会导致灾难性的失效，例如超音速飞行器的结构损坏。尽管非定常激波在高速空气动力学中具有临界性质，但我们对激波振荡控制机制的理解存在关键差距，这是本文提出的动机。在这里，我们进行了实验，采用最先进的基于图像的技术，如高速纹影可视化和粒子图像测速，来检查非定常SWBLI动力学。特别是，将对冲击强度如何影响非定常振幅和频率内容进行详细研究，以改进目前没有考虑冲击强度影响的模型，使其能够更好地预测实验观测结果。

Shock wave–boundary layer interaction (SWBLI) where a close coupling exists between the boundary layer and the outer supersonic flow occur frequently in high-speed engineering applications. One of the striking features of SWBLI is an unsteady shock front that oscillates about the mean position. The shock oscillation can lead to an elevated surface pressure fluctuation level, which when strong enough may lead to a catastrophic failure, e.g. structural damage in a supersonic vehicle.Despite the critical nature of unsteady shock in high-speed aerodynamics, critical gaps exist in our understanding of the mechanism that governs the shock oscillation, which serves as a motivation for the present proposal. Here, we conduct experiments that employ the state-of-the-art image-based technique, such as high-speed schlieren visualisation and particle image velocimetry, to examine the unsteady SWBLI dynamics. In particular, a detailed investigation of how the shock strength influences the amplitude and the frequency contents of the unsteadiness will be conducted to improve current models, which do not take into consideration the effects of the shock strength, such that they are better able to predict the experimental observations.