Highly resolved simulations of of air-water interaction during the breaking of extreme waves

In this lecture, the air-water interaction phenomena occurring in the breaking of free surface waves are discussed. The studies are conducted by using numerical solvers of the Navier-Stokes equations for a variable density fluid. Interface capturing techniques are used to describe the complicated free surface topologies developing during the breaking process. The highly resolved simulations allow to examine many aspects of the flow which cannot be investigated experimentally. Two different mechanisms are adopted to induce the breaking: a first one representative of the breaking occurring nearby the coasts, and a second one closer to the open ocean conditions. Results are presented in terms of free surface dynamics, air entrainment and droplets ejection, velocity and vorticity fields, energy dissipation and momentum transfer in air and water. The changes operated by the breaking on the prebreaking spectrum are analyzed as well. The limits of the most relevant assumptions are discussed along with the ways in which the obtained results may be exploited in practice.