Outflow of a supersonic overexpanded air jet into a water

Abstract

Numerical simulation of the underwater outflow of a supersonic overexpanded air jet is considered. The calculations are carried out in an unsteady three-dimensional formulation with a hybrid approach using Reynolds-averaged Navier–Stokes equations for nozzle flow and large eddy-simulation for jet flow. The calculation of the interaction of a gas with a liquid is performed with a volume of fluid, which takes into account the surface tension and compressibility of water. The structural features of turbulence when a supersonic air jet exhausted into water are analyzed. An unsteady formation of a supersonic jet and a gas cavity in a water is obtained, the shock-wave structure of the flow is visualized and the level of pressure fluctuations in water is reported. A comparison of the flow pattern when an air jet exhausted into air and water is made on a qualitative level. The results of numerical simulation of the jet velocity field are used to analyze the Kelvin–Helmholtz and Rayleigh–Taylor instability mechanisms and to reveal the dominant instability mechanism in different jet propagation regions. The results obtained are compared with experimental high-speed photographic recording data and numerical calculations At a qualitative level in literature.