The bursting of a toroidal bubble at a free surface

This paper is concerned with the bursting of a large bubble at a free surface. The numerical modelling is based on the boundary integral method. To validate the numerical model, experiments are carried out for the bursting of a spark generated bubble at a free surface in a low pressure tank, captured by using a high speed camera. Our numerical results agree qualitatively with the experiments. We further carry out numerical analysis for the bursting of an underwater explosion bubble at a free surface. We have considered the bursting of singly connected bubbles as well as toroidal bubbles. When a bubble is initiated very close to a free surface, the bursting occurs during the expansion phase, thus, resulting in a cone shaped spike at the free surface. However, when the bubble is initiated away from the free surface, it expands and collapses below the free surface and rises to the free surface due to buoyancy. An upward liquid jet forms during the later stage of collapse, which subsequently penetrates through the bubble. The toroidal bubble rises and bursts at the free surface, which results in a much higher water column due to the high speed bubble jet.