The modelling of large individual waves for the computation of loads on ships and oshore structures in extreme weather conditions is still a challenging problem. Since the early 50's the predictions of loads on fixed offshore structures and motions of compliant or sailing structures due to surface waves are commonly made by computations on the basis of the statistical/spectral description of the sea elevation. This approach, based on the linear wave model, is now an almost common procedure and it has been recognised that it works reasonably well for the so-called operational conditions.

On the other hand, it is also recognised that the modelling of the waves in the so-called survival conditions, i.e. extreme wave conditions with very low occurrence probability, cannot recast a linear approach and the wave-wave interaction plays a fundamental role (energy transfer, down-shift, etc).

In this work the nonlinear aspects related to the energy exchange between Fourier components of steep focusing breaking and non-breaking waves are analysed
by means of numerical simulations and new experiments. The experiments are carried out in the wave flume of the Coastal Engineering Laboratory of the Dept. of Civil and Environmental Engineering of the University of Florence.
The computations are carried out at HyMOLab at the Dept. of Engineering and Architecture of the University of Trieste with OpenFOAM, adopting a VOF technique at the free surface.

This study is part of the research project "OpenViewSHIP - Development of an integrated computational ecosystem for the hydrodynamic design of the hull-propeller system",cofinanced by Friuli Venezia Giulia Region in the held of industrial application of
open-source CFD and High Performance Computing.