In order to design a floating OWC (Oscillating Water Column)-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 frequency domain is proposed. The fluid motion in water waves is calculated by using boundary element method based on velocity potential theory. For the air flow in air chamber, an equation of state,conservation of mass and energy with the assumption of air being the perfect gas are used. From these equations, motions of floating body, air pressure in air chamber, transmission and reflection coefficient of water waves and primary conversion efficiency etc. are calculated. Wave tank tests are also carried out for BBDB in regular waves. Numerical results are compared with experimental results.
