The Effect of Hydrodynamics on the Power Efficiency of a Toroidal Oscillating Water Column Device

Abstract

This study tries to identify the effect of hydrodynamics on the absorbed wave power using a toroidal Oscillating Water Column (OWC) device. To this end, the fundamental hydrodynamic boundary value problem for an arbitrary shaped toroidal OWC device of revolution with vertical axis is solved. The described method is based on the discretization of the flow field around the device by means of ring-shaped macro-elements, in each of which axisymmetric eigenfunction expansions for the velocity potential is made. The solution sought for the corresponding diffraction and radiation velocity potentials is achieved using Galerkin’s method. The applied formulation is generic and can be employed for arbitrary configurations of toroidal OWCs. Therefore, the numerical results shown and discussed in the present paper, in terms of the hydrodynamic loads and the air volume flows inside the OWC chamber, concern different types of OWCs. From the present analysis, it is demonstrated that the absorbed wave power by the examined toroidal devices is strongly affected by the geometrical parameters of the device; thus, these should be properly considered towards the maximization of the device’s wave power efficiency.