Modeling of Freak Wave Generation In a 3D-NWT

Abstract

Freak waves are extreme ocean waves that are not predicted by traditional wave probability distributions. We study wave energy focusing, as a possible mechanism for freak wave formation, in a three-dimensional (3D) Numerical WaveTank (NWT) solving fully nonlinear potential flow equations. The NWT combines a higher-order 3D-BEM and a Mixed-Eulerian-Lagrangian time updating of the free surface, based on explicit second-order Taylor series expansions. Self-focusing of wave energy is achieved through modulating a periodic wave train in two orthogonal directions. This process is first carried out using a Higher Order Spectral method whose solution is then introduced in the NWT, in whichwe specify space periodicity conditions on lateral boundaries. Directional and frequency focusing of waveenergy are achieved through using a snakewavemaker to generate curved wave fronts at one extremity of the NWT, and specifying an actively absorbing open boundary condition at the other extremity of the NWT. Breaking and non-breaking freak waves are generated in the NWT and their shape and kinematics are studied.