Study on the influence of incoming flow velocity on thrust stability of underwater solid rocket motor

Submerged supersonic gaseous jets are typically found in underwater rocket propulsion, forming a complex multiphase transient system which affect the performance of propulsion seriously. Numerous early studies are focus on gaseous jets injected into quiescent water, but in most exact application scenario of underwater propulsion, gaseous jets are injected into dynamic water flow. This paper studies the unsteady characteristic of submerged gaseous jets and the thrust stability of underwater rocket propulsion systems with focus on the influence of ambient incoming flow velocity. A two-dimensional axisymmetric geometric model and the Volume of Fluid (VOF) multi-phase flow model is adopted for simulation calculation. The simulation results, verified by relevant experiment, indicate that there is a significant difference between the flow structure of gaseous jets injected into dynamic water flow and that entering still water. As the incoming flow velocity increases, the amplitude of pressure oscillation near the exit of the nozzle decreases. To a certain extent, the stability of the thrust is enhanced with the increasing inflow velocity, correspondingly.