Numerical investigation on the flow structure of gaseous jet horizontally injected into water for underwater propulsion

The jet propulsion powered by a solid propellant rocket or hybrid aluminum combustor(HAC) is a new, promising underwater propulsion method which can be adopted in the high speed naval vehicles. The hot gaseous jet for underwater propulsion is a typical process with both gravity and buoyance, which will have a significant influence on the flow field structure and thrust of the motor. A numerical simulation for the horizontal gaseous jet effects in deep underwater has been presented in this paper, which mainly consists of three parts. Firstly, a 3-D numerical simulation using the volume of fluid (VOF) model was established to get the jet structure of underwater solid rocket motor induced by both the gravity and the buoyancy and the deep understand of the mechanism of thrust oscillation characteristics. Secondly, the analysis on flow field structure and the thrust oscillating characteristics in the initial period of working was conducted using the principle of momentum. Finally, the analysis on the length or slope of the straight jet related to the working conditions under the influence of gravity and buoyancy has been conducted. Comparing the trajectories in different conditions, it can be concluded that the length of jets increases while the thrust reduces, which is just opposite as what happened in a closed zone.