Numerical study of underwater jet characteristics of an annular conical aerospike nozzle

Abstract When a solid rocket engine ignites underwater, the tail jet undergoes periodic evolution. To study the underwater over-expansion and separation flow structure of the aerospike nozzle under different high backpressure environments, a numerical model of the underwater jet multiphase flow of a solid rocket engine was established based on the Volume of Fluid (VOF) model and Shear Stress Transport (SST) k - ω model. The validity of the model was verified by comparing it with the experimental data. Then, a numerical simulation study of the aerospike nozzle jet was conducted under different water depth environments. The results show that a solid rocket engine working underwater is different from one working in air. The oscillation of the underwater flow separation flow field of the aerospike nozzle is mainly affected by the jet oscillation process induced by the gas–water two-phase interaction. The larger the depth, the more intense the phenomenon of bulging, necking, and back-attack of the motor jet. The high-temperature aggregation area at the end of the jet gradually approaches the tail wall with the increase in depth. With the increase in engine ignition depth, the pressure distribution on the nozzle tail wall surface transitions from steady-state oscillation to intense oscillation, and the instant of violent pressure oscillation advances. The engine thrust first increases, then decreases, and subsequently increases again.