On the evolution of supercavity geometry and unsteady behavior of supercavitation flow during the development of a twin-vortex supercavity

Abstract

To investigate the evolution of supercavity geometry and the unsteady characteristics of the supercavitation flow from the initial generation to full development. A three-dimensional numerical model with the inhomogeneous multiphase model and SST k−ω turbulence model was established. The numerical model was validated by experimental results. The ventilated supercavitation flow was performed under the different gas entrainment coefficients and Froude numbers. The results show that the initial supercavity closure mode is the re-entrant jet, then the closure mode changes to the twin-vortex induced by the gravitational effect. For the fully developed twin-vortex supercavity, a flow structure with gas recirculation exists inside the supercavity, which includes the reverse flow region and downstream flow region. Compared to the supercavity with the twin-vortex closure mode, the increment in the supercavity dimension with the re-entrant jet closure mode increases drastically, and the oscillation characteristic of internal pressure increases, leading to the significant supercavity deformation and gas shedding. The difference of the supercavity dimension is revealed by analyzing the gas leakage behavior. Further, a theoretical model describing the strength of re-entrant jet is established to reveal the transition mechanism of the supercavity closure mode and analyze the unsteady flow characteristics during the supercavity development.