Internal Flow Aerodynamic Oscillation Characteristics of Launch Vehicle Configuration

A reusable launch vehicle (RLV) typically reenters with its base, resulting in flow penetration and oscillation inside the combustion chamber, which may potentially affect the aerodynamics. In the case of a hybrid RLV, because the body itself functions as the combustion chamber, the effect of the flow inside a chamber may be significant, and the shape of the chamber could vary depending on fuel consumption during ascent. This study examined the flow and aerodynamic characteristics of a hybrid RLV during reentry. The internal pressure measurements were analyzed, confirming that the internal flow oscillations were a result of Helmholtz resonance. Considering the shock standoff distance, the internal flow oscillations directly induced shock wave oscillations in the models with a chamber depth of 40 mm. However, for the model with a chamber depth of 90 mm, abrupt shock wave oscillations were observed, and this tendency was also found to affect the drag. This was attributed to the partial stagnation effect at the nozzle throat caused by the interference between the inflow and outflow in the chamber with a specific depth-to-diameter ratio. This may lead to flow recirculation at the nozzle throat, which, in turn, affects the shock wave and aerodynamic oscillation characteristics.