Free surface wave generation and breaking induced by underwater explosion

This study investigates the interaction between a bubble and the free surface during an underwater explosion, focusing on its evolution under near-surface conditions (γ < 0.3). Using numerical simulations and electro-spark experiments, the research examines the post-fragmentation motion of the bubble and its relationship with the stand-off parameter γ and the buoyancy parameter δ. The results showed that during the bubble expansion phase, both bubble dynamics and free surface evolution are significantly influenced by the stand-off and buoyancy parameters. After the bubble breaks through the free surface, it either forms an “Exposed-bottom cavity” phenomenon or a closed cavity. The “Exposed-bottom cavity” is associated with bottom buoyancy and annular bubble rupture. Further analysis showed that the maximum bubble radius decreases as the stand-off parameter increases, while it remains positively correlated with the charge weight, with more pronounced variations for W < 20 kg. The maximum deviation between the numerical results and the mathematical model reaches 7.8%. In addition, the water lip height generally increases with charge weight and exhibits a turning point at approximately γ = 0.16, which shifts further as the charge weight increases. The maximum fitting error between the mathematical model and the numerical results reaches 11.2%.