Numerical Study of Supersonic Retro-Propulsion Flow Characteristics based on Low-Altitude Descending Flight Mach Numbers

This study presents a comprehensive investigation of SRP (Supersonic Retro-Propulsion) flow characteristics of a small launch vehicle equipped with a rocket engine.CFD (Computational Fluid Dynamics) simulations were conducted under free-fall conditions to examine the influence of descending flight Mach number and MFR (Mass Flow Ratio) on the flow field surrounding the base rocket body and nozzle.When SRP is applied, the flow behavior is strongly dependent on MFR.At lower MFR values, direct interaction between the bow shock and exhaust plume causes the high-temperature jet to envelop the base body, with wall temperatures exceeding 2000 K.In the intermediate MFR regime (7.8-9.3), the exhaust plume becomes the dominant factor, while Mach disk formation promotes turbulence and heating within the plume wake, leading to reduced wall temperatures on the base body.For MFR values exceeding 10, the flow undergoes a transition from SPM (Short Penetration Mode) to LPM (Long Penetration Mode).This LPM is characterized by an elongated exhaust jet, a weak downstream bow shock, and extensive recirculation zones.Overall, the results demonstrate that low MFR values induce strong plume-shock interactions and high thermal loads on the rocket body, whereas higher MFR values shift the flow dominance to the exhaust plume, mitigating heating effects.