Muzzle flow field characteristics of underwater sealed launch system under different projectile shapes

Abstract

The underwater sealed launch is one of effective launch technologies for enhancing the velocity of underwater vehicle and also for achieving better interior ballistic performance. However, the underwater muzzle flow field based on this sealed technology is a major consideration as it decides initial kinetic stability and subsequent shooting accuracy. Hence, this study establishes a comprehensive model involving in a modified sealed interior ballistic model, muzzle multiphase turbulent flow model and supercavitation model due to high-velocity moving vehicle, and mainly investigates the effect of the vehicle shapes on the underwater sealed muzzle field. An experiment for the muzzle field of underwater sealed launch is also carried out using a 12.7 mm-caliber launch device and water tank. Comparisons on flow patterns of muzzle field and expansion displacements of Taylor cavity on computational results are done with experimental studies, and a reasonable match has been obtained in these comparisons. The results show that the gas sealed in the launch barrel firstly injects into the water forming an initial Taylor cavity once the sealed device is broken. Then, the propellant combustion-gas just with high pressure and high temperature injects into the water with the moving vehicle. Consequently, a complicated interaction effect between these two types of gases and high-density water takes place, generating complicated shock wave phenomena in the muzzle field. Different vehicle shapes can affect the formation of the shock waves and expansion characteristics of Taylor cavity in the water. Eventually, the diameter of the Mach disk is always the largest for the cylindrical underwater vehicle and the axial pressure fluctuation for the vehicle with a cavitator are most significant with a lowest temperature field due to strong gas-liquid interaction.