Air entrainment and degassing process in breaking waves

The air entrainment and the degassing process in breaking waves is investigated. The ow generated by the breaking of free{surface waves of dierent initial steepnesses is simulated numerically, through a two- uids Navier-Stokes solver combined with a Level-Set technique for the interface capturing. The ow is assumed two-dimensional. The evolution of periodic wave trains of dierent initial steepness is considered. For large initial steepnesses the breaking is of the plunging type and leads to the entrappment of large air cavities, area of which is found to scale as the steepness to the power seven.The fragmentation process of the large air cavities is analysed and quantitative estimates of the amount of air entrapped by the breaking and of the degassing process are provided.