Dynamics of inner gas during the bursting of a bubble at the free surface

Abstract

In the present study, simulations are directed to capture the dynamics of evacuating inner gas of a bubble bursting at the free surface, using Eulerian based volume of fluid (VOF) method. The rate by which surrounding air rushing inside the bubble cavity through the inner gas evacuation is estimated and compared by the collapsing bubble cavity during the sequential stages of the bubble bursting at the free surface. Further, the reachability of inner gas at different horizontal planes over the unperturbed free surface is estimated. The evacuating inner gas accompanies vortex rings, which entrains the surrounding gas-phase. During the successive stages of air entrainment, spatiotemporal characteristics of the vortex ring are obtained. At low Bond numbers (Bo < 1), the axial growth pattern of gas jet and the radial expansion of jet tip are studied with the phase contour of evacuating inner gas. Furthermore, the axial growth of rising inner gas over the free surface and the radial expansion of vortex rings of a bubble bursting at the free surface is compared with the quiescent surrounding air under the respiration process. At last, the effects of various possible asymmetric perforation of the bubble cap keeping the same Bo are studied. The cause of the bent gas jet, as a consequence of the perforation of the bubble cap, asymmetrically, is explained by plotting the velocity vectors. The effect of miscibility on the spreading dynamics of inner gas has been found to be minimal at the early stage of the bursting process.