Fully nonlinear simulation of wave interaction with a cylindrical wave energy converter in a numerical wave tank

Convergence and accuracy of fully nonlinear time-domain simulation of wave interaction with a submerged cylindrical wave energy converter oscillating about an off-center axis which was conducted using a two-dimensional numerical wave tank are examined in this study. A high-order boundary element method is used to compute the fluid flow in the Eulerian frame. Fully nonlinear boundary conditions are applied to achieve the unique solution of the boundary value problem. Hence, kinematics of the fluid particles on the exact free surface boundary is calculated using the material node approach in the Lagrangian frame. Runge-Kutta time integration is employed to update the boundary values and the computational control volume. To implement the body condition, the time derivative of the velocity potential is computed implicitly using the acceleration potential. An artificial wave maker and two artificial sponge layers are provided to retain the open water condition. The power absorption efficiency of the submerged Bristol cylinder is compared with experimental data and numerical solutions for different incident waves to verify the present numerical model and the accuracy of the solution is also investigated. The convergence of the present fully nonlinear model in the simulation of the freely rotating cylinder about the off-centered axis as a wave energy converter is evaluated for different submergence depths, off-center distances, and a robust nonlinear incident wave.