Numerical modelling of new flap-gate type breakwater in regular and solitary waves using one-fluid formulation

Breakwater is commonly used infrastructure for protecting coastal zones from waves and tsunamis. Computational modelling is frequently employed for prediction and validation of the breakwater design. Potential flow based models may not be ideal for such applications due to large energy dissipation. We apply the Computational Fluid Dynamics (CFD) to study the waves and breakwater interaction problem. In this work, we benchmark the performance of a new type of flap-gate breakwater in regular waves (airy wave theory and second order Stokes wave theory), where the multiphase Navier–Stokes equations are solved and the structure of breakwater is considered as one phase of fluid within the ‘one-fluid’ framework. In this way, the computational costs will be reduced to the same level as the numerical wave tank alone. We conduct a grid refinement study and compare results to experiments to investigate accuracy. The result shows a good agreement with the experimental data. Further, we use the validated model for sensitivity studies for different settings of flap-gate, and the solitary waves paradigm for tsunamis. The proposed novel numerical tool allows us to study large parametric spaces, impact of breaking waves, load and pressure producing process and interaction time.