水下超声速气流流场非定常特性研究

The floating rocket mine experiences a large change of environment pressure during operation. In order to simulate the working process of the underwater rocket engines, utilizing the VOF multiphase model, an axisymmetric model describing gas jet in different working states (under-expansion, full-expansion, over-expansion) of underwater engine was established. By simulating the working states with 0m/s and 50m/s, the evolution of the gas jet and unsteady flow characteristics under different working conditions were studied. With velocity 0m/s, the positon of neck shrinkage is far away from the nozzle, and the pulsation of mass flow rate and pressure is not obvious in under-expansion condition. In addition, under full-expansion and over-expansion conditionsmass flow rate and pressure is not obvious in under-expansion condition. In addition, under full-expansion and over-expansion conditions, the positon of neck shrinkage is closer to the nozzle. The maximum pressure amplitudes at nozzle outlet are 5.5MPa, 7MPa, respectively. Correspondingly, oscillation amplitude of mass flow rate is 5.2%, 32.8%. With upstream velocity 50m/s, the positon of neck shrinkage, bulge and back-attack is far away from the nozzle. The maximum pressure amplitude at nozzle outlet under full-expansion is 2MPa, and the pulsation of mass flow rate disappears. The maximum pressure amplitude at nozzle outlet under over-expansion condition is 6.1MPa, correspondingly, and the oscillation amplitude of mass flow rate is 30.4%.