Analysis of Bubble Coalescence Dynamics and Postrupture Oscillation of Capillary-Held Bubbles in Water

This paper presents a three-dimensional computational study of coalescence dynamics of two capillary-held air bubbles in water using the volume of fluid (VOF) method. The interface motion of the newly formed bubble indicated that smaller initial separation distances resulted in a slightly faster expansion of the neck. The velocity vectors showed that the inward motion of the air at the contact point of the two bubbles favors the generation of small eddies at the top and bottom part of the neck at the early stage of coalescence and bulges at the edges of the bubble at a later stage. The release of free-surface energy drove the bubble contraction and expansion and consequently the oscillation motion, which created differences in pressure across the bubble interface. The computationally simulated bubbles followed the oscillatory motion observed experimentally, but with a lower damping constant and lower angular frequency.