Air-Water Interaction in Breaking Waves

The two-dimensional free surface flow generated by periodic wave trains of different amplitudes is investigated. The flow in air and water is simulated numerically through a two-fluids Navier-Stokes solver. The method makes use of an interface capturing technique for the modeling of the free surface dynamics. Depending on the initial steepness of the wave train, regular waves, spilling breaking waves or plunging breaking waves are found. The peculiar aspects of the free surface dynamics in the three regimes are analyzed and the differences in the flow field induced in air and water by breaking of growing strengths are discussed. A detailed study of the circulations and of the energy contents in the air and water domains is presented. According to well established experimental observations, it is shown that the wave breaking significantly enhances the energy dissipation. The role of wave breaking in the vorticity production is highlighted. It is found that the circulation increases significantly when the breaking changes from spilling to plunging whereas it is independent of the initial steepness in the plunging breaking regime.