Two-dimensional numerical modelling of a novel heaving wave energy converter-perforated breakwater integrated system

Abstract

Through numerical modelling, the hydrodynamic performance of a novel wave energy converter-breakwater integrated system, consisting of a perforated breakwater and a heaving wave energy converter (HWEC) in the wave absorption chamber, is investigated. A method for modelling the Coulomb damping force (CDF) provided by the power take-off system is established to address the instability problem caused by the sudden change of the CDF when the motion direction of the HWEC changes. Under the representative wave condition ($kd$ = 1.76, where $k$ is wave number and $d$ is water depth), the working mechanism of the integrated system is clarified, the preferable HWEC hull shape is found, and the nondimensional relationships for determining the geometric parameters are obtained. In addition, by performing the simulation with the waves of $kd$ = 2.52 and $kd$ = 1.11, the limits of the geometric parameters are proposed. It is found that the asymmetric HWEC having a seaward straight corner and leeward curved corner is preferable to minimize wave reflection and capture appreciable wave energy. Under the tested condition, when the nondimensional PTO damping force ranges from 0.5 to 1.25 and the response amplitude operator of the HWEC is no less than 0.3, the capture width ratio of the integrated system will mostly exceed 0.3, and the reflected energy will be quite low.