Numerical study for nonlinear hydrodynamic coefficients of an asymmetric wave energy converter

Abstract

In this study, the nonlinear dynamic behavior of an asymmetric Wave Energy Converter (WEC) was studied on a 1/11-scale model based on a numerical and experimental method in a regular wave field. The numerical analysis involved both frequency-domain and time-domain solutions. The frequency-domain solution was based on linear potential flow theory using the WAMIT® model whereas the time-domain solution was based on the Reynolds-Averaged Navier-Stokes (RANS) equation using the OpenFOAM® model. The pitch response amplitude operators obtained from the numerical results were compared with experimental data. Additionally, the nonlinear dynamic behavior of the asymmetric WEC due to various wave heights and periods obtained through the experiments were compared with the OpenFOAM results. Wave excitation moments and hydrodynamic coefficients based on the linear solution approach were separately obtained for the fixed asymmetric WEC induced by waves and the forced oscillating motion with OpenFOAM. Moreover, frequency-domain solutions based on linear potential flow theory were obtained in order to ascertain the nonlinear effects observed in the OpenFOAM results. It was found that a higher motion amplitude could be attributed to nonlinear hydrodynamic coefficients on the asymmetric WEC calculated by the forced oscillation motion of the RANS-based solution.