Pressure characteristics of a nonspherical underwater explosion bubble in a compressible fluid

Abstract

The pressures produced by underwater explosions present serious threats to ships, submarines, and other marine structures. A significant part of underwater explosion pressure comes from the explosion bubble. Most computational studies on bubble pressure have considered the case of an incompressible fluid or have confined calculations to the time before the formation of a toroidal bubble, because of the complexity and strong nonlinearity of a compressible flow field with a doubly connected geometry. The few compressible models that are capable of calculating the pressure after jet impact suffer from computational difficulties. In this paper, we calculate the bubble pressure by constructing a new form for solving an auxiliary function based on a boundary integral method that takes account of the compressibility of the flow field. We verify out numerical algorithm by comparison with a classical theoretical model and a set of experimental results. We then compare the bubble pressure in a compressible flow field in both the first and second oscillation periods with that in an incompressible flow field. The results of this comparison confirm that it is necessary to consider the compressibility of the fluid and the multiperiod pulsations of a bubble in pressure calculations. We present a comprehensive discussion of the pressure characteristics in the central axial and circumferential directions induced by a nonspherical bubble in a free field. Finally, we obtain a critical bubble-wall distance r w > 1.8 for which the bubble is prevented from splitting after the first jet impact, and we investigate the pressure characteristics of a bubble near a rigid wall for both cases of r w < 1.8 and r w > 1.8.