Modal analysis of mixing characteristics in scramjet combustor with passive struts

The combustion occurs at supersonic velocities in a scramjet engine. Since the mixing and combustion take place at high velocities, analyzing the mixing of air and fuel in the engine is of great interest for many researchers. In the present study, two passive struts are placed at a short distance downstream of the fuel injection strut. The effect of these passive struts in the mixing of air/fuel are assessed. Hybrid RANS/LES simulation is conducted using an improved delayed detached eddy simulation (IDDES) turbulence model. The single strut configuration is compared with the different strut configurations. The mixing efficiency is highly affected by the placement of the strut. The mixing performance is found to be superior in the strut configuration having high back-pressure. The modal analysis found the different modes that were responsible for the mixing enhancement at different sections of the combustor. The modes have high intensity when close to shock-shear layer interaction (SSLI), this suggests that SSLI are important for mixing enhancement. The broadband noise are observed in all the configurations due to large-scale mixing. Dynamic mode decomposition (DMD) reveals the modes responsible for the peak amplitude in the noise.