Large eddy simulation of film cooling mechanism in supersonic mainstream

Large eddy simulation was employed to investigate the interaction between a sonic jet and a supersonic mainstream within the context of compressible film cooling. A computational framework in OpenFOAM has been developed to efficiently capture shock waves, vortex structures, and boundary layer interactions, incorporating adaptive mesh refinement and dynamic load balancing to reduce computational costs. The approach was validated qualitatively with shock waves and vortex structures and quantitatively with velocity distribution. The hydrodynamic effects of jet separation and reattachment in crossflow were investigated, including the impact of shock waves, boundary layers, and vortex structures on cooling efficiency. The results show that, the cooling region appears an arrow-like shape when a sonic separation and reattachment jet enters a supersonic crossflow. As the Mach number increases, the shock wave system becomes more pronounced, altering the cooling film's surface attachment capability and affecting overall cooling performance. In the downstream of the jet, the formation and development of the vortex system play a decisive role on the cooling efficiency. Additionally, the initial vortex system at the leading edge of the jet hole not only controls upstream cooling but also plays a crucial role in the formation of the overall cooling structure through its entrainment and mixing capabilities. As the Mach number of the mainstream increases, the initial vortex system carries more cooling energy, thereby improving overall cooling efficiency. Moreover, the interaction between shock waves and vortex structures influences the angle between turbulent heat flux and the temperature gradient, a more accurate model is needed to analyze the turbulent heat flux.