Expansion characteristics of multiple wall jets in cylindrical observation chamber

Abstract

The objective of this study is to investigate the drag reduction effect of a new launch technology by utilizing propellant gases to drain off water in the front of the projectile inside the gunbarrel for submerged launch process of underwater gun. A static analogue visualized device was designed and the high-speed digital photographic system was adopted to investigate expansion processes of multiple wall jets in cylindrical observation chamber. The evolution laws of Taylor cavities can be obtained by dealing with the expansion sequence maps. Based on the experiments, a three-dimensional unsteady mathematical model is established to simulate the interaction process between the multiple wall jets and liquid medium, which can achieve the detailed distribution characteristics of phase, pressure, temperature and velocity in flow field. Results show that, by increasing four wall jets to eight wall jets, the decrease of the inlet turbulent kinetic energy of each jet leads to a decline in the initial axial velocity. However, the Taylor cavities achieve to converge more quickly for the case with more numbers of combustion-gas jets due to less nozzle interval distance. In addition, the convergence of Taylor cavities can enhance the drainage effect of the multiple wall jets and achieve excellent drag reduction effect for the underwater launching process, wherein the drainage effect for the case of six wall jets is the most outstanding.