Mechanisms of jet mixing in a supersonic crossflow: A study using large-eddy simulation

High-order compact differencing/filtering schemes are coupled with recently developed localized artificial diffusivity methodology in the context of large-eddy simulation (LES) to obtain insights into the physics of an under-expanded sonic jet injection into a supersonic crossflow. The flow conditions of the experiment by Santiago and Dutton [J. Prop. Power. 13 (1997) 264-273] are selected for detailed simulation. The present LES qualitatively reproduce the unsteady dynamics of both barrel shock and bow shock as observed in the experiment. It found that pressure fluctuation inside the upstream recirculation region induces unsteadiness of windward jet shear layer and causes large-scale dynamics of the barrel shock and front bow shock. Statistics obtained by the LES also show good agreement with the experiment. With regard to the processes controlling the jet mixing we studied the dynamics of vortex structures in the flow. Two regions of vortex formation which form hairpin-like structure are identified in the windward and leeward jet boundaries. These vortices play an important role in determining the behavior of jet fluid stirring and subsequent mixing. Also noted is the entrainment of rolled-up windward shear layer by the upstream recirculating flow.