Jet development and impact load of underwater explosion bubble on solid wall

Abstract

The damage effects of an underwater explosion have always been a crucial problem in the ship mechanics. Notably, the bubble evolution and the jet impact load are one of the most difficult parts in the shock-resistance design of ship structures due to the discontinuities and significant nonlinear deformation. In this paper, the Eulerian finite-element method is introduced to continuously simulate the shock wave and non-spherical bubble evolution stages near a horizontal solid wall with the volume of fluid method and pressure balance technique used to resolve the multi-medium flow. The numerical model is established in a cylindrical coordinate system and validated by comparing the results with a spark-generated bubble experiment. After that, based on the present model, the shock wave propagation and the bubble evolution are simulated to study the characteristics of the impact loads of an underwater explosion. Besides, the influences of the wall location (upside or downside) and the stand-off distance from the wall are also analyzed. The results show that the features of the jet impact load are much more complicated than those of the shock wave. Nearby a downside wall, the buoyancy and Bjerknes force compete to dominate the bubble motion with opposite influences. By contrast, They enhance the effect of each other to develop a liquid jet towards the upside wall. The pressure peak, impact range, and duration time nonlinearly depend on the combination of the case parameters and are not monotonic to a single one. Within a proper range of the parameter combination, the jet impact load can reach its maximum and be more destructive than the shock wave because of a comparable pressure peak and a much longer duration.