The development of more efficient ramjet engines has motivated the study of enhanced mixing in compressible shear layers. Cavity-mixer is a widely used passive flow control tool, but its mixing enhancement mechanisms in compressible subsonic-supersonic shear layers has yet to be comprehensively explored. In this work, a cavity-mixer is used to increase mixing in a subsonic-supersonic shear layer, and the underlying flow control mechanisms are examined. Parametric experiments were performed on a laboratory-scale blowdown wind tunnel and an extraction wind tunnel. Numerical simulations were performed in a large eddy simulation framework. Schlieren and nanoparticle-based planar laser scattering techniques were adopted for mixing flow visualization. It is found that the growth rate of the cavity (length-to-depth ratio of 5) disturbed shear layer is 31% higher than the benchmark configuration at convective Mach number of 0.49∼0.56. It is demonstrated that the compressibility and length-to-depth ratio affect the cavity-mixer performance. High convective Mach number suppresses the cavity disturbance and weakens its mixing enhancement efficiency. Cavity-mixer with a length-to-depth ratio of 3 shows the highest experimental and numerical growth rate, compared to 5 and 7 under a convective Mach number around 0.49. Large-scale coherent vortices are confirmed in the subsonic-supersonic mixing process. Cavity disturbance promotes the three-dimensional characteristics of the flow field, increases the vorticity of large coherent structures, and advances the K-H instability position of shear layer, which plays a key contribution to mixing enhancement.

效率更高的冲压发动机的发展激发了对可压缩剪切层中增强混合的研究。空腔混合器是一种广泛使用的被动流动控制工具，但其在可压缩亚音速-超音速剪切层中的混合增强机理尚未得到全面探索。在这项工作中，使用腔混合器来增加亚音速-超音速剪切层中的混合，并研究了基本的流量控制机制。参数化实验是在实验室规模的排污风洞和抽风风洞上进行的。在大型涡流模拟框架中进行了数值模拟。采用Schlieren和基于纳米粒子的平面激光散射技术进行混合流可视化。研究发现，在对流马赫数为0.49〜0.56的情况下，受干扰的剪切层（长深比为5）的生长速率比基准构型高31％。结果表明，可压缩性和长深比影响腔混合器的性能。高对流马赫数抑制了空腔干扰并削弱了其混合增强效率。长径比为3的腔混合器显示出最高的实验和数值增长率，而在对流马赫数为0.49时，则为5和7。在亚音速-超音速混合过程中证实了大规模相干涡旋。空腔扰动促进了流场的三维特性，增加了大型相干结构的涡度，并提高了剪切层的KH不稳定性位置，