Outflow of a supersonic overexpanded air jet into a water

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.