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Implementation of an opposing jet in design of a hypersonic blunt body significantly modifies the extal flowfield and yields a considerable reduction in the aerodynamic drag. This study aims to investigate the effects of flowfield modeling parameters of injection and freestream on the flow structure and aerodynamics of a blunt body with an opposing jet in hypersonic flow. Reynolds-Averaged Navier-Stokes (RANS) equations with a Shear Stress Transport (SST) turbulence model are employed to simulate the intricate jet flow interaction. Through utilizing a Non-Intrusive Polynomial Chaos (NIPC) method to construct surrogates, a functional relation is established between input modeling parameters and output flowfield and aerodynamic quantities in conc. Sobol indices in sensitivity analysis are introduced to represent the relative contribution of each parameter. It is found that variations in modeling parameters produce large variations in the flow structure and aerodynamics. The jet-to-freestream total-pressure ratio, jet Mach number, and freestream Mach number are the major contributors to variation in surface pressure, demon-strating an evident location-dependent behavior. The penetration length of injection, reattachment angle of the shear layer, and aerodynamic drag are also most sensitive to the three crucial param-eters above. In comparison, the contributions of freestream temperature, freestream density, and jet total temperature are nearly negligible.