Supersonic flows past the morphing cavities with different ramp angles of the trailing wall are studied by the direct numerical simulation (DNS) method. As the ramp angle increases, the sound pressure level of the dominant mode and overall sound pressure level gradually decrease at the last monitor point. The number of the feedback shock waves and the size of the large-scale vortices also gradually decreases. The vortex wave moving downstream slowly disappears. When the ramp angle increases to 30 and 40 degrees, the dominant mode at the front of the cavity shifts from mode 3 to mode 1. In addition, the flow structures in the morphing cavities are analyzed using proper orthogonal decomposition (POD). Results indicate that the energy occupied by the POD modes, the size of the flow structures, and the amplitude of POD coefficients all decrease with the ramp angle increase. Compared with the fixed-geometry cavity with the ramp of the trailing wall, the results show that there is a better noise reduction effect and the flow structure is changed in the morphing cavity. In a word, the morphing cavity control method effectively suppresses cavity noise, greatly weakens the sensitivity of the shear layer, and obviously changes the flow structure in the cavity.

通过直接数值模拟（DNS）方法研究了超声速流过尾随壁的不同倾斜角度的变形腔的情况。随着倾斜角度的增加，主导模式的声压级和总体声压级在最后一个监听点处逐渐降低。反馈冲击波的数量和大型涡旋的大小也逐渐减小。向下游移动的涡旋波逐渐消失。当倾斜角度增加到30度和40度时，腔体前面的主导模式从模式3转变为模式1。此外，使用适当的正交分解（POD）分析变形腔体中的流动结构。结果表明，POD模式占用的能量，流动结构的大小，POD系数的幅值均随斜坡角的增加而减小。结果表明，与带有尾壁斜面的固定几何腔相比，变径腔具有更好的降噪效果，且流动结构发生了变化。总之，变型腔控制方法有效地抑制了腔噪声，大大削弱了剪切层的敏感性，明显改变了腔内的流动结构。