On the births of jet drops from bubbles bursting on water surfaces

Abstract

The parameters of the births of jet droplets originating from bubbles bursting on water surfaces are presented. Results are given for bubble sizes R b from 350‐ to 1500‐μm equivalent volume radius in both sea and fresh waters. The ejection speeds of the jet droplets generated by a collapsing bubble and the height above the surface, as well as the time, at which the top drop breaks off the ascending jet have been measured. The dependence of the average droplet speed s e on bubble size is shown to be an exponential for at least the top two drops. For the top drop this dependence is given by s e = 10.7 exp (−0.00127 R b) m s−1 for R b in micrometers which is a fit to measurements between 350‐ and 1500‐μm radius. Extrapolated to small bubble size, this equation projects that the maximum droplet speed of ejection will approach 10.7 m s−1 as bubble size vanishes. Extrapolated to larger bubbles, on the other hand, this equation projects that a bubble with R b = 3000 μm will emit a droplet with a speed of only 0.2 m s−1. The time t that the top drop separates from the rising jet is given by t = 2.45×10−5 R b1.65, where R b is in micrometers and t is in milliseconds.