With the rapid development of technologies for scramjet and combined-cycle engines, the efficient mixing of supersonic airflow and fuel within the combustor has become a key factor limiting engine performance improvement. Existing research has predominantly focused on Mach number and compressibility effects, while systematic analysis of the influence of Reynolds number remains scarce. In this study, the large eddy simulation (LES) method is employed to investigate the effects of inflow Reynolds number on the flow structures, growth characteristics, and modal evolution of a supersonic mixing layer. By adjusting the inlet pressure, three different Reynolds number conditions are established, and the evolution of vortex structures, development of mixing layer thickness, turbulence statistics, and dynamic mode decomposition (DMD) characteristics are analyzed. The results indicate that under high Reynolds numbers, the transition in the mixing layer occurs earlier, vortex breakdown intensifies, three-dimensional features become more pronounced, and the mixing layer centerline shifts significantly toward the low-speed side. The energy spectrum in the self-similar region exhibits approximate isotropy, and the inertial subrange expands with increasing Reynolds number. Moreover, DMD analysis reveals that flow field reconstruction at high Reynolds numbers requires higher-order modes, reflecting richer dynamic scales. Our study elucidates the influence of Reynolds number on the multi-scale evolution mechanisms of supersonic mixing layers, providing a theoretical basis for the prediction and control of mixing processes in high-speed propulsion systems.
Chen et al. (Fri,) studied this question.