Direct numerical simulations of non-reacting and reacting sonic hydrogen jets injected into supersonic crossflows

In this study, direct numerical simulation was performed to investigate the shock and flow characteristics of a sonic hydrogen jet injected into a Mach 3.38 turbulent boundary layer without and with chemical reactions. It is found that the interaction between the shock waves and turbulence in the windward shear layer is intensive, with sharp compression leading to a temperature increase, resulting in a minimal difference of thermal and flow structures between the two cases. In the reacting case, combustion mainly occurs in the fuel-rich region, with a higher reaction intensity on the windward side that decays as the jet develops, while combustion is weaker on the leeward side. Quantitative analysis shows that combustion slightly reduces the streamwise velocity near the wall, increases the normal velocity, and influences both turbulent kinetic energy and Reynolds stresses. On the windward side, the maximum temperature increases by about 5% compared to the non-reacting case due to heat release, leading to a slight reduction in turbulence intensity, while on the leeward side, turbulence intensity near the wall is enhanced. Combustion also suppresses turbulence intensity near the bow shock. The vorticity dynamics was examined, showing that vortex stretching and volume expansion are the main contributors of vorticity generation in the windward side. Combustion slightly increases the volume expansion term in the upstream recirculation and shear layers, and significantly enhances the baroclinic term in the windward shear layer.