Dilute Oil-in-water Emulsion Promotes Multiple Holes Formation During Bursting of Centimetric Bubble*

Bubble bursting and resulting aerosol generation have been extensively investigated due to their direct relevance in varying industrial and environmental settings. Most previous studies focus on water or surfactant-laden bubble, however, under real-world conditions, particles or droplets are inevitably presented. The current experimental study concerns centimetric bubbles containing microscopic solid particles or oil droplets, with sizes relevant to the bubble cap film thickness at breakup. The oil droplets' spreading coefficient varied from 3.6 to 21.3 mN/m. A bubble column array setup has been designed to simultaneously measure bubble lifetime, bubble bursting dynamics, and aerosol formation using both high-speed imaging and digital inline holography. The results show that the dispersed phase in water can significantly affect the bubble lifetime and bubble cap retraction velocity. With the increase of the gas-liquid interfacial spreading coefficient, the average film retraction velocity decreases and the average film thickness increases. In particular, a distinct phenomenon as multiple-hole formation on the bubble cap was documented for bubble bursting in oil-in-water emulsions, due to the perforation of the oil into the air-water interface. The results demonstrate the great impact on bubble bursting dynamics and resulting aerosol generation in real-world contaminated water containing microscopic impurities with varying sizes and concentration.