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 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 air chamber, an equation of state and the conservation of mass and energy with the assumption of air being the 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 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 results.
The Many types of wave energy converters (WEC) that are based on various concepts have been proposed in recent years (Cruz (2008)). Methods evaluating energy absorbed from the waves by such converters were also shown (Falnes(2002)). This device has some advantages, that is,
the primary conversion efficiency is higher than other floating OWCs,
as the wavelength for which primary conversion efficiency is maximum is about four times the length of the BBDB, a longer floating structure is not required, iii) as BBDB slowly advances against wave propagation direction in particular wave frequency band, the mooring force and mooring cost are deduced in irregular waves.
