Bursting Droplets from Bubble Plumes: Influence of Subsurface Bubble Characteristics on Droplet Production

The bursting of surface bubbles plays a critical role in transporting small particles and contaminants from water to air. We experimentally studied droplets ejected by bursting bubbles from bubble plumes generated by either an air stone or a single nozzle, across a range of gas flow rates (0.1–0.8 L/min). High-speed imaging revealed that, compared to the single nozzle, the air stone produced up to 20 times more droplets, 8.6 times higher mass flow, and 1.8 times larger median size, demonstrating the strong influence of subsurface bubble characteristics. Both droplet size and velocity distributions followed log-normal trends across all conditions. We found that the median droplet size scales with bubble size as R_d~R_b^1.4, implying a Bond number scaling of Bo_d~Bo_b^1.4. Furthermore, a universal scaling relationship was identified: La_d~Ca_d^-1.4 for the characteristic length and velocity of droplets, and Fr_d~(Bo_bWe_b)^-0.3, providing predictive power for droplet dynamics from bursting bubble plumes.