Effects of floaters' hydrodynamics on the performance of tightly moored wave energy converters

This study investigates the effect that several different floaters' geometries have on the performance characteristics of tightly moored vertical axisymmetric wave energy converters (WECs) A cylindrical buoy with and without vertical and horizontal skirts mounted at its bottom, a cone, as well as two piston-like arrangements, consisting of an internal floater (cone or cylinder) and an exterior torus, have been examined and comparatively assessed The WEC's first-order hydrodynamic characteristics are evaluated using a linearised diffraction-radiation semi-analytical method Axisymmetric eigenfunction expansions of the velocity potential are introduced into properly defined ring-shaped fluid regions surrounding the bodies and the potential solutions are matched at the boundaries of adjacent fluid regions by enforcing continuity of the hydrodynamic pressures and radial velocities A dynamical model for the floaters' performance in time domain is developed that properly accounts for the floater's hydrodynamic behaviour, the coupling terms between the different modes of motion and of the power take-off mechanism Numerical results are presented and discussed, in terms of the expected power production The results show parametrically the effect that the varying hydrodynamic characteristics of each particular floater's geometry have on the investigated WEC's performance characteristics