Investigation of the dynamics of inner gas during bursting of a bubble at the free surface

TL;DR

This study uses simulations to analyze the dynamics of inner gas evacuation during bubble bursting at the free surface, focusing on vortex formation, gas jet behavior, and effects of cap perforation.

Contribution

It provides detailed insights into the inner gas dynamics, vortex ring characteristics, and effects of asymmetric bubble cap perforation during bursting, using Eulerian VOF simulations.

Findings

Inner gas evacuation is accompanied by vortex rings entraining surrounding air.

Axial growth and radial expansion of gas jets vary with Bond number and perforation symmetry.

Asymmetric perforation causes bent gas jets explained by velocity vector analysis.

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 over the free surface is evaluated by establishing the comparison of the same through various horizontal planes, lying at different altitudes above the unperturbed surface. 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 (< 1), after comparing the phase contours of evacuating inner gas from the bubble cavity, the consequences at the axial growth of gas jet and the radial expansion of the jet tip is discussed separately. Furthermore, under the respiration process, 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. At last, the effects of various possible asymmetric perforation of the bubble cap keeping the same Bo are studied. The cause of bent gas jet, as a consequence of perforation of the bubble cap, asymmetrically, is explained by plotting the velocity vectors.