Effect of Free-Stream Mach Number on the Base Thermal Environment of Launch Vehicle

Convective heating of the rocket base caused by high-temperature reverse flow has long been a focus of thermal protection research. With distinctive structural characteristics, the base thermal environment of a twin-nozzle engine proves more susceptible to the recirculation region than its multi-nozzle counterparts. During the transonic stage, significant alterations in the flow field structure at the rocket base strongly influence the recirculation region. This study investigated the thermal environment of the rocket base with a twin-nozzle configuration in freestream at Mach numbers of 0.6 to 3.0. Results indicate that the freestream Mach number significantly affects the thermal environment at the rocket base during the transonic stage. The increase of Mach number from 0.6 to 1.0 causes the convective heating of the rocket base to increase by 7.7 times. This phenomenon arises due to the plume-induced shock wave caused by the impact of the supersonic free shear layer and plume shear layer while the flight speed exceeds the sound speed. The interaction between the shock wave and the shear layer amplifies turbulence in the recirculation region and at the inflection point, resulting in a stronger high-temperature reverse flow. In addition, the cause of low-altitude base heating was analyzed, and it was found that the mechanism is different from the high-temperature countercurrent effect caused by plume interaction.