  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.
