Formation and dynamics of bubbles generated by turbulent breaking waves

Turbulent breaking waves in oceans entrain air pockets that break up and coalesce to form a polydisperse cloud of bubbles. The size distribution of super-Hinze scale bubbles is compatible with one due to the quasi-steady fragmentation of large air pockets by turbulent eddies in an inertial subrange, but the distribution of sub-Hinze scale bubbles, for which capillary stresses dominate turbulent stresses, remains a subject of active research. In this study, an ensemble of simulations of statistically-unsteady breaking waves is used to investigate the temporal evolution of these distributions. This requires the proper identification of bubbles in each ensemble member at individual time instances. Physical bubbles are distinguished from numerical bubbles by a grouping algorithm that identifies resolved bubbles without clipping their mass. The resulting ensemble-averaged distributions of bubble sizes momentarily exhibit power-law scalings that compare well with experimental findings. The power laws suggest a quasi-steady transfer of bubbles in radius space. A collision detection algorithm is employed to identify impacts between surfaces and investigate rates of breakup and coalescence, which contribute to changes in the relative proportions of bubble sizes over time.