Bubble and free surface dynamics in shallow underwater explosion

In this study, the volume-acceleration model was introduced to determine the initial conditions for bubble motion during underwater explosions. Subroutines, which define the initial and boundary conditions of the fluid field, were developed based on the MSC.DYTRAN software. Numerical simulations were compared with the results of validated experimental data. The calculated shapes of the bubbles are in excellent agreement with the experimental results. Using the interaction between a bubble and a free surface as basis, we simulated and analyzed the dynamic behavior of a bubble near a free surface, including the ring rebound of the bubble and the spray dome of the free surface. The computed spray dome heights are consistent with the results from empirical formulas. The dynamic behavior of the bubble and the spray dome of the free surface were systematically studied and summarized in accordance with the principle that bubble motion and the spray dome are closely related to standoff distance. The results of this study may serve as reference for understanding bubbles formed by underwater explosions and those generated by laser. They also have valuable implications for correlative theory research and engineering calculations.

► We develop a subroutine based on MSC.DYTRAN to define the initial and boundary conditions of fluid field.
► We examine the interaction between a bubble and a free surface on underwater explosion.
► Direction of liquid jet depends on the standoff distance between bubble and free surface.
► A downward liquid jet is formed while the standoff distances within 1.5 times the value of maximum radius of bubble.
► Velocity of liquid jet increases as standoff distance decreases.