Numerical investigation of an underwater explosion bubble based on FVM and VOF

Dynamics of the underwater explosion (UNDEX) bubble in a free field is numerically investigated in the present paper using a compressible two-phase flow solver. The finite volume method (FVM) is adopted for discretization of the Navier-Stokes equations. The volume of fluid (VOF) method is utilized to capture the bubble-water interface. Validation is carried out against the Gilmore model for a spherical bubble and an experiment for the aspherical UNDEX bubble subjected to buoyancy. The bubble expansion, collapse, high-speed liquid jet and the rebounding are well predicted. Meanwhile, the propagating pressure waves can be clearly captured. The pressure and velocity fields within and surrounding the bubble are described in detail. For the UNDEX bubble subjected to strong buoyancy effect, the jet impacts on the opposite side in a small region rather than at a single point. Splitting of some tiny bubbles can be observed in the jet impact area. The toroidal bubble undergoes splitting and coalescence subsequently. Additionally, non-uniform distribution of the velocity of the gas in the bubble could be observed almost in the entire bubble life while the pressure field inside the bubble is quite uniform. Lastly, the jet dynamics as well as the migrating behaviors of the bubble under the effect of buoyancy is carefully investigated.