The influence of flow separation mode on side-loads in a rocket nozzle

Side-loads in nozzle can cause serious structural damage. Owing to the presence of side-loads of a rocket nozzle in the actual environmental situation, the unsteady flow field of the nozzle, which is based on dynamic mesh technology, has been simulated by taking VOLVO S1 nozzle. The study calculates the flow field and side-load in the nozzle when the pressure ratio is from 4 to 16, and comprehensively studies the generation and evolution of the shock wave shape, so as to analyze the influence of the internal flow separation on the side-load under different conditions of the nozzle. The results show that the nozzle flow separation mode will significantly affect the side-load, mainly in the following: when the nozzle is in the free shock separation mode, the airflow in the nozzle passes through the shock wave, occurs separation and then no longer adheres to the wall surface, while the side-load is obvious. As the pressure ratio increases, the asymmetry of flow separation occurs inside the nozzle and the side-load gradually increases with it. The nozzle flow is close to the critical state of the conversion of the shock separation until NPR=7.The severe pressure asymmetry of the upper and lower walls occurs inside the nozzle, accompanied by serious side-load. Subsequently, the nozzle flow transforms into the restricted shock separation, which is uniform and stable, and the side-load tends to a small amount in value.