A CFD simulation of a full-scale U-OWC breakwater

Many different concepts of marine renewable energy sources are currently being developed. Wide research efforts are focused on OWC systems, that are under study for onshore as well as floating applications. In this work, we carried out a CFD experiment on a full-scale U-OWC breakwater able to simulate both the flow field in front of breakwater and the flow field inside the OWC device, taking into account of the characteristics of the air turbine adopted as power take-off device. These simulations aim therefore to analyse the wave-structure interaction in terms of reflection and transmission coefficients and the overall performance of the system. The breakwater is supposed to be operated under regular waves generated by a piston type wave maker. In order to reduce the huge need of computational resources, CFD unsteady simulation have been carried out in a two dimensional (2D) reference frame by solving the Reynolds-Averaged Navier-Stokes (RANS) equations while the water-air interaction is taken into account by means of the Volume Of Fluid (VOF) model. In order to simulate the oscillating flow across the air turbine in 2D CFD simulations, a new method has been also proposed here. Considering that the air pressure is about uniform, the ceiling of the chamber has been modelled by means of a computational domain (porous zone) where analytical equations able to model the exchange of mass and energy across the air duct and the turbine are implemented. A further outcome of the work is the calibration of the analytical model used for performance analysis and control system design.