Effect of expansion waves on cowl shock wave and boundary layer interaction in hypersonic inlet

The interaction of cowl shock wave and boundary layer has a crucial effect on the stability, operability and performance of hypersonic inlets. Many studies on inhibiting the separation and managing the strength of the interaction of the shock wave and boundary layer with expansion corner have been conducted. However, the expansion waves near the circular arc shoulder to effectively control the interaction and cowl shock arrangement is little investigated. Therefore, the interaction of the cowl shock wave and boundary layer under the fluence of the expansion waves is studied by inviscid and viscous numerical simulations. The results reveal that the expansion waves have an important impact on the interaction between the cowl shock wave and boundary layer and the strength of shock wave, and that there are four types of interaction processes with the change of the relative impingement positions of cowl shock wave. The expansion waves have a different influence on the shock wave and boundary layer interaction at different incident points. When the incident point of the cowl shock wave goes far downstream from the end of the circular arc shoulder, the influence of expansion waves is weakened, and the magnitude of separation zone increases. However, when the expansion waves are applied to the interaction of the cowl shock wave and boundary layer on the circular arc shoulder, the separation can be effectively controlled. In particular, while the expansion waves interact with the shock wave and boundary layer in the back half of the circular arc shoulder, the separation is best inhibited. Compared with the upstream and downstream incident points, the scale of separation area in the optimal control region is reduced by 65.3% at most. Furthermore, the total pressure recovery coefficient first increases and then decreases when the cowl moves from upstream to downstream, and the total pressure recovery coefficient reaches the maximum value of 68.36% at the incident position of cowl shock wave d = 8.09δ₀.