Effects of splitter plate geometric configurations on mixing layer behavior in supersonic reacting flows

Mixing layers are key flow structures and canonical models for investigating supersonic combustion. This study investigates four distinct splitter plate configurations: sp, sp-cavity, sp-strut, and sp-step, via computational fluid dynamics (CFD) simulation. Validation of the CFD results against experimental data confirms its accuracy in simulating supersonic combustion processes. Key findings reveal significant differences in growth mechanisms between the sp-cavity configuration and the others. Specifically, case sp-cavity exhibits a distinct “vortex–cavity-excitation resonance-driven” mechanism, while the remaining cases follow a “shock-mixing layer interaction-driven” mode. In particular, the resonance between the vortex structures and the high-frequency excitation associated with the cavity self-sustained oscillations influences burning patterns, resulting in more regular combustion zones in the sp-cavity case compared with the other cases. The maximum thickness occurs at tunnel exit, with case sp-step reaching 29 mm (the highest value) and case sp-cavity achieving 21 mm (the lowest), representing a 38% increase in mixing layer thickness for sp-step. Total pressure loss distributions are similar among configurations, with case sp-step experiencing the largest total pressure loss of 0.205.