Frequency Domain Analysis on Primary Conversion Efficiency of a Floating OWC-type Wave Energy Converter

Abstract

In order to design a floating OWC-type wave energy converter such as Backward Bent Duct Buoy (BBDB) it is necessary to develop a numerical method to make clear an optimal hull shape which maximizes the generating electrical energy. In this paper, a two-dimensional numerical method to estimate the primary conversion efficiency of a floating OWC-type wave energy converter with arbitrary cross section in the frequency domain is proposed. The fluid force by water waves is calculated by using boundary element method based on velocity potential theory. For the air flow in the air chamber, an equation of state and the conservation of mass and energy with the assumption of air being a perfect gas are used. From these equations for the air flow, boundary integral equation for the velocity potential and equations of motion of the floating body, motions of floating body, air pressure in the air chamber, the transmission coefficient and reflection coefficient of water waves and primary conversion efficiency etc. are calculated. Wave tank tests for the primary conversion efficiency of BBDB in regular waves are also carried out and numerical results are compared with experimental result.