Two-Dimensional Numerical Simulation of Underwater High-Speed Gas Jet and Complex Wave System

Aiming at the generation and development of underwater high-speed gas jet, based on the Euler two-fluid model and the space-time conservation element and solution element(CE/SE) method, a model of jet with high speed and high pressure in free water is established, and the gas-liquid two-phase numerical simulation of the external flow field of underwater nozzle is carried out to analyze the flow field characteristics of initial jet, as well as the complex wave systems and shapes in the process of underwater high-speed gas jet injection. And the phenomenon of “hitting back” inside the jet is preliminarily discussed. The results show that the flow field presents slow axial development and rapid radial expansion due to the blocking effect of water after the underwater gas jet injection at high speed. A complex wave system in which the leading shock wave, the reflected shock wave and the intercept shock wave cross each other is formed in the high pressure zone of the gas front. The interaction of complex wave systems makes the jet develop downstream continuously with an axial concave shape, and irregular shape of the main jet interface appears. The gas retrospecting phenomenon occurs in the process of jet propagation, which leads to the “diamond” shape in the jet. The complex change of the flow field pressure at nozzle outlet caused by propagation of wave systems and their interaction has an important effect on the propulsion performance of underwater engines.