Bubbles bursting at contaminated water surfaces aerosolize oil, microplastics and bacteria, with consequences for public health and climate. The classical description, in which a draining cap ruptures at a single hole and the retracting rim fragments into film droplets, was established for clean or surfactant-laden liquids. How dispersed oil droplets, which may occur in dispersant-treated spills and industrial wastewater, reshape rupture topology and droplet yield has remained unclear.
In this seminar, after briefly outlining my laboratory and field multiphase-flow thrusts at GTIIT, I present our experiments on centimetric bubbles that (i) reveal multi-hole rupture, previously unreported on a bubble cap, in which oil droplets with a positive spreading coefficient, comparable in size to the cap thickness, excavate thin spots and up to 47 holes open in a single burst, (ii) show that bubble lifetime still sets the film thickness through capillary-viscous drainage, which oil accumulated at the bubble foot retards through Marangoni stress, and (iii) establish a drop-yield law, growing as the square root of the hole number through the active rim length, that collapses the multi-hole data onto one master curve. The first hole forms preferentially near the foot, a second about 2 ms later, and the rest cascade at intervals of order 0.1 ms, after which colliding rims form a convoluted ligament network that can generate an order of magnitude more droplets than the classical scaling predicts. I also discuss the surprising finding that a tenfold increase in oil fraction leaves the film thickness at a given lifetime unchanged yet raises the probability of multi-hole bursting from 2.3% to 40.1%, with this probability and the droplet yield both peaking within a lifetime window of 4 to 9 s, in which the film is thin enough to rupture yet persists long enough for further holes to form. I close with the open question of what triggers the sub-millisecond cascade.
