Dynamics of an Underwater Explosion Bubble near a Rigid Wall: Effect of Slenderness Ratio, Installation, and Distance Parameter

Structural damage of maritime construction (e.g., dams, warships, etc.) has received considerable international attention in recent years because of underwater explosions from accidental events and terrorist bombing attacks. Therefore, research studies on underwater explosion load characteristics will have a great influence on the future of coastal and maritime engineering. Here, level set-direct ghost fluid-Runge Kutta discontinuous Galerkin method and boundary element method are combined to establish a model of underwater explosion near a rigid wall. First, the hybrid algorithm is used to simulate the process of underwater explosion in free field; the results agree well with experimental data, proving the effectiveness of the algorithm. Second, the process of underwater explosion near a rigid wall is simulated by the presented method. Finally, effects of parameters - slenderness ratio, installation (horizontal and vertical), and distance from the center of the explosive to the rigid wall - are investigated on shock waves and bubble dynamics. It is found that during the detonation process, the ellipsoidal bubble gradually turns into a spherical one. The radial pressure peak value is higher than the axial one. During the collapse phase, the slenderness ratio and the installation have little effect on bubble shape, maximum radius, and pulsation cycle. During the bubble-jet process, a high-speed jet penetrates the bubble toward the rigid wall and generates a high-pressure region on the bubble wall. For the charge placed vertically, the jet velocity rises while the jet width decreases as the slenderness ratio increases; results for horizontal cases are opposite. The jet velocity in the vertical case is lower than that in the horizontal case; on the contrary, the jet width is larger. With the increase of the distance parameter, the pressure on the upper surface of the bubble and the jet velocity are higher, whereas the jet width is smaller.