Experimental and Numerical Studies of Underwater Explosions

摘要

The dynamics of bubbles formed during underwater explosions is numericallyinvestigated using an Arbitrary Lagrangian-Eulerian three-dimensional finite-element code. The expansion and the collapse of a vapor bubble in a water tank is first simulated to compare the predictions with data from a parallel experimental study. Experimental and numerical results show good qualitative and quantitative agreement and suggest that the excitation of Rayleigh-Taylor instability is a major cause of bubble interface instability. This observation is consistent with earlier data and confirms that interface instability plays a significant role in the loss of energy from the explosion. Simulations have also been carried out to investigate bubble-bubble and bubble-wall interactions. Results from the bubble-bubble interaction studies show the formation of a water jet as one bubble collapses into the other, in agreement with recent experimental observation. The collapse of a bubble near a rigid wall and the formation of high velocity re-entrant jet onto the wall has also been successfully simulated. The peak impact pressure and the fluid flow velocity agrees well with the experiments. In addition, the well known vortex ring bubble during the collapse process has been numerically captured. Application of the computational methodology to realistic deep sea explosions and to detonation cords used for mine destruction has also been carried. Results of these studies are also discussed in this report.