Numerical study on strong nonlinear interactions between spark-generated underwater explosion bubbles and a free surface

•Strong nonlinear interactions between one and two underwater explosion bubbles with a free surface are numerically studied.•Numerical method is based on axisymmetrical fully compressible three-phase homogeneous model coupled with two interface advection equations.•Numerical and experimental data agree well regarding the shape of bubbles and free surface.•Detailed pressure and velocity contours during the interaction process are obtained and can better reveal the mechanism underlying the dynamics between the bubbles and free surface.•Motion characteristics of the free surface and bubbles are investigated under different non-dimensional standoff parameters. In this study, strong nonlinear interactions of one and two underwater explosion bubbles with a free surface are numerically studied using an axisymmetrical fully compressible three-phase homogeneous model. The bubble interfaces and free surface are captured by solving two interface advection equations of vapor and air phases. The numerical results are validated via comparisons with the experimental results. The single-bubble case is validated first, and good quantitative and qualitative agreements are achieved. Special features of the interactions, such as jet impact, toroidal bubble, and primary and secondary water spike, are observed in our numerical model. The detailed pressure and velocity contours during the interaction process are obtained and can better reveal the mechanism underlying the bubbles and free surface dynamics. Afterward, the characteristics of the motion of the free surface and the bubbles are investigated considering different non-dimensional standoff parameters. Four distinct patterns of free surface motion are identified. Next, strong interactions between two bubbles and a free surface are simulated. The essential physical phenomena, such as coalesced bubble, annular residual, and bubble splitting, are reproduced well in the representative experiments. Finally, a parametric study reveals the dependence of the center water spike on the interaction between the bubbles and the free surface. Evolution of strong nonlinear interaction between a spark-genarated underwater explosion bubble with a free surface. Special characteristic motions including jet impact, toroidal bubble, center and secondary free surface spike are well captured with experimental images. [Display omitted]