Breaking focused wave interaction with cylinder using HOS-OpenFOAM coupling

Extreme waves endanger offshore structures under severe environmental conditions. These large and steep waves are highly nonlinear, which can cause high-intensity and short-duration impact forces. It is vital to understand the impact created by such extreme events over any structure. The objective is to investigate wave impact forces on a vertical surface piercing cylinder subjected to breaking waves. The numerical simulation is carried out with a hybrid coupled solver named foamStar. It couples a High-Order Spectral (HOS) based nonlinear potential model and an OpenFOAM based CFD model.The HOS model describes accurately in a fully nonlinear potential flow framework the focused breaking wave without the structure. The CFD model is based on the incompressible Reynolds-averaged Navier-Stokes equations and the volume of fluid for the free surface. The coupled model is a CFD based numerical wave tank. First, the focused wave onset of breaking is validated in HOS-NWT and foamStar, and then its interaction with the cylinder is addressed. The experimental results used in this paper correspond to the experiments performed in Ludwig-Franzius-Institute, Germany[1]. The experimentally measured main wave crest of the breaking focused wave group with its total forces and pressure over a cylinder is fairly well captured in the numerical simulation. Further, the evolution of focused breaking waves along the tank and their characteristics were examined. An overall good degree of agreement is reported, which denotes that the model can be a helpful tool to evaluate breaking wave forces on structures.