A direct simulation Monte Carlo (DSMC) method is utilized to numerically investigate rarefied hypersonic flows over a group of two-dimensional rectangular cavities with rounded separation/reattachment corner. The effects of the rounded separation/reattachment corner on flow characteristics are discussed. The sensitivities of aerodynamic surface quantities are hence assessed comprehensively. Flows over the cavity configurations specified in the study hold the “open-cavity” characteristics and do not show any unsteadiness. The rounded separation corner does not significantly alter the flow patterns, while the rounded reattachment corner has a remarkable effect. Rounding the separation and reattachment corners can weaken the baroclinic effect in the separation and reattachment regions, respectively. For the rounded separation corner, it is easier for external gas molecules to enter the cavity and hence promote the momentum and energy exchanges with gas molecules inside the cavity. The fluid density inside the cavity, peak density at the reattachment point, pressure on and heat fluxes to the cavity floor are augmented, compared to those in the rectangular cavity case. However, the rounded reattachment corner may enhance the escape of gas molecules from the cavity and weaken the exchanges of momentum and energy. This leads to a significant decrease in the gas density inside the cavity, peak gas density at the reattachment point, pressure on and heat fluxes to the cavity floor. It is concluded that the approach of rounding the reattachment corner can achieve the most dramatic drop in the peak pressure and heat flux at the reattachment point. The research is guidable to the aerodynamic design of local configuration of hypersonic vehicles.

利用直接模拟蒙特卡洛（DSMC）方法对一组具有圆形分离/重新连接角的二维矩形腔体上稀疏的高超音速流动进行数值研究。讨论了圆形分离/重新连接角对流动特性的影响。因此，对空气动力学表面量的敏感性进行了全面评估。研究中指定的腔体构造上的流动具有“开放腔”特征，并且不会显示任何不稳定情况。倒圆角的分离角不会明显改变流型，而倒圆角的重新连接角则具有显着效果。使分离角和重新连接角变圆可以分别减弱分离和重新连接区域中的斜压效应。对于分离的圆角，外部气体分子更容易进入空腔，从而促进与空腔内部气体分子的动量和能量交换。与矩形腔体情况相比，腔体内部的流体密度，重新连接点的峰值密度，腔体底部的压力和通向腔体底板的热通量都增加了。但是，圆形的重新连接角可能会增强气体分子从腔中逸出并削弱动量和能量的交换。这会导致空腔内部的气体密度，重新连接点的峰值气体密度，空腔底部的压力和热通量显着降低。得出的结论是，使重新连接角变圆的方法可以在重新连接点实现最大的峰值压力和热通量下降。