A comprehensive numerical study is performed to reveal influence of the upstream wall slope on aerodynamic properties as rarefied hypersonic flows pass through the two- and three-dimensional cavity configurations using the direct simulation Monte Carlo (DSMC) method. In this work, slope effect is obtained by the cavity upstream wall sloping upward and downward as well as bulging partially. Besides, cases of freestream with different velocities and altitudes are taken into account to examine the slope effect. It is found that cavity flow is transformed from the open type to the transitional and finally to the closed as the cavity upstream wall gradually slopes upward, promoting the heat energy exchange between gas molecules with the cavity floor, and meanwhile achieving a considerable rate of decrease of the peak heat flux on the reattachment corner. However, the upstream wall sloping downward or bulging partially seems to only have a slight effect on cavity flow and wall heat flux. It's worth noting that slope effect is closely related to velocity and altitude of the freestream, such as the greater the velocity and altitude, the stronger the slope effect. For the three-dimensional cavity configuration, influence of the upstream wall slope on cavity flow and wall heat flux is weaken considerably due to the three-dimensional effect. From the perspective of optimal design for the hypersonic thermal protection system, the cavity with an upward upstream wall is proposed because it not only reduces peak heat flux on the reattachment corner, but also decreases gas temperature inside the cavity.

使用直接模拟蒙特卡罗 (DSMC) 方法，进行了全面的数值研究，以揭示当稀薄的高超音速流通过二维和三维腔配置时上游壁坡度对空气动力学特性的影响。在这项工作中，通过向上和向下倾斜以及部分凸起的空腔上游壁获得斜坡效果。此外，考虑了具有不同速度和高度的自由流的情况来检查坡度效应。研究发现，随着腔体上游壁逐渐向上倾斜，腔体流动从开放型转变为过渡型，最后转变为封闭型，促进了气体分子与腔底的热能交换，同时实现了重接角处热通量峰值的大幅度降低。然而，向下倾斜或部分凸起的上游壁似乎对腔流和壁热通量只有轻微影响。值得注意的是，坡度效应与自由流的速度和高度密切相关，速度和高度越大，坡度效应越强。对于三维空腔配置，由于三维效应，上游壁面坡度对空腔流动和壁面热通量的影响大大减弱。从高超声速热防护系统优化设计的角度，提出了上游壁向上的空腔，因为它不仅减少了再附着角处的峰值热通量，