Air entrainment and bubble statistics in three-dimensional breaking waves

Abstract eng:
We investigate air entrainment and bubble statistics in three-dimensional breaking waves through novel direct numerical simulations of the two-phase air-water flow. The dissipation due to breaking is found to be in good agreement with previous experimental observations and inertial-scaling arguments. For radii r larger than the Hinze scale, the time-averaged bubble size distribution is consistent ¯ (r) ∝ r−10/3 scaling, as observed experimentally. Moreover, we find that the time dependent and time averaged bubble size with a N distribution scale linearly, respectively, with the time dependent and time averaged dissipation rate due to the breaking event. Based on these numerical results, existing laboratory data, earlier models, and the balance between mechanical dissipation and work done against buoyancy forces, we propose a phenomenological turbulent bubble break-up model, that describes both the bubble size distribution and the total volume of entrained air, as a function of the external wave parameters.

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