Numerical and experimental study of the hydrodynamic coefficients and power absorption of a two-body point absorber wave energy converter

Abstract

This study compares the hydrodynamic coefficients of a two-body point absorber wave energy converter (WEC) model obtained by three methods, namely the experimental method, the finite volume method (FVM), and the boundary element method (BEM). The BEM and FVM numerical simulations of the WEC motion are done using ANSYS AQWA and OpenFOAM, respectively. An experimental method for the accurate calculation of the added mass, damping coefficient, and wave excitation force for the WEC is introduced. The experiments are carried out in a wave tank with a scaled-down WEC model. A comparison of the results shows that – although the BEM is computationally fast, inexpensive, and able to estimate the added mass of the WEC with a reasonable accuracy – it is not able to accurately calculate the damping coefficients. The power absorbed by the WEC is calculated using the hydrodynamic coefficients obtained by all methods. The results show that the viscous damping dramatically decreases the absorbed power. A practical range of dimensionless damping coefficients is proposed to estimate the viscous damping of a two-body point absorber WEC, based on the experimental and FVM results. The upper bound of the absorbed power is also discussed in this paper.