Flow topology and unsteady cavitation dynamics in the wake of a backward facing step was investigated using high speed videography and time-resolved X-ray densitometry, along with static and dynamic pressure measurements. The measurements are used to inform the understanding of underlying mechanisms of observed flow dynamics as they are related to shock wave induced instabilities. The differences in cavity topology and behavior at different cavitation numbers are examined to highlight flow features such as the pair of cavitating spanwise vortices in the shear layer and propagating bubbly shock front. The shock speeds at different cavitation conditions are estimated based on void-fraction measurements using the X-T diagram and compared to those computed using the one-dimensional Rankine Hugoniot jump condition. The two speeds(computed and measured) are found to be comparable. The effect of compressibility of the bubbly mixture is determined by estimating the local speed of sound using homogeneous ‘frozen model’ and homogeneous ‘equilibrium model’. The current estimation of sound speed suggests that expression used to determine the local speed of sound is closer to the classic ‘frozen model’ than the ‘equilibrium model’ of speed of sound.

使用高速摄像和时间分辨X射线光密度法，以及静态和动态压力测量，研究了向后走步之后的流动拓扑结构和非定常空化动力学。由于与冲击波引起的不稳定性有关，因此这些测量值可用来帮助您了解所观察到的流体动力学的基本机理。检查了在不同空化次数下腔拓扑和行为的差异，以突出流动特征，例如剪切层中的一对空化展向涡旋和传播的气泡状激波锋。使用XT图根据空隙率测量值估算不同空化条件下的冲击速度，并将其与使用一维兰金·霍根尼奥特跳跃条件计算的冲击速度进行比较。发现两个速度（计算的和测量的）是可比较的。通过使用均质的“冻结模型”和均质的“平衡模型”估计声音的局部速度，来确定气泡混合物的可压缩性的影响。当前对声速的估计表明，用于确定声速的局部表达式比声速的“平衡模型”更接近经典的“冻结模型”。