Flow structure evolution and aerodynamic scaling of supersonic retropropulsion during hypersonic reentry

This study investigates the effects of Supersonic Retropropulsion (SRP) on flow structures and aerodynamic loads during the vertical landing of reusable launch vehicles. A combined approach utilizing hypersonic wind tunnel experiments and Reynolds-averaged Navier-Stokes simulations is employed to systematically analyze the evolution of SRP-induced flow interference under varying freestream and thrust conditions. The investigation focuses on the complex interaction mechanisms between the retropropulsive jet and the hypersonic freestream, the evolution characteristics of vortex ring structures and their modulation of flow unsteadiness, as well as the quantitative relationships between characteristic flow scales and thrust parameters. The results show that SRP significantly alters the aerodynamic loading and flowfield topology in the aft-body region. The introduction of angle of attack induces asymmetric vortex ring evolution and large-scale low-frequency disturbances, which further affect the dynamic stability of the triple-point, shock structures, and recirculation zones. Under asymmetric conditions, the angle between the vortex core line and the wind tunnel axis rapidly decreases from 90° to 72.13° within 300 μs, corresponding to a transverse expansion velocity of 73.3 m/s. These asymmetric dynamics exhibit markedly stronger evolution rates and flow modulation compared to symmetric cases. Both experimental and numerical results consistently show a linear relationship between the locations of key flow structures and the square root of the thrust coefficient ( C T ). Additionally, the maximum Mach number increases almost linearly from 5.77 to 6.73 with increasing C T , showing minimal sensitivity to angle of attack. These findings enhance the physical understanding of SRP flow interference and offer valuable guidance for the development of predictive aerodynamic models and control strategies.