Backward Bent Duct Buoy (BBDB) which has a bent center-pipe opened to the lee side of the incident waves is a kind of moored floating OWC-type wave energy converter. In this paper, in order to make clear the fundamental characteristics of BBDB, three-dimensional experiments in waves for motions of five different BBDB models are carried out. Motions of 6 degrees of freedom of BBDB, pressure and water levels in the air chamber, etc. are measured. From the experiments, fundamental characteristics of BBDB such as the relationship between motions of BBDB and pressure in the air chamber according to the changes of the body shape of BBDB are obtained.
Many kinds of wave energy converters have been proposed in recent years. Backward Bent Duct Buoy (BBDB) is a wave energy converter of moored floating oscillating water column type which is composed of an air chamber, horizontal duct and buoyancy chamber and turbine as shown in Fig.1. The mouth of the horizontal duct in underwater is faced away from the waves. As BBDB has the advantage that the primary conversion performance is better than other floating type devises and mooring force is smaller than others because BBDB advances in the incident wave direction with slow-speed, BBDB is said to be one of the best type converter among proposed wave energy converters. Some researchers are investigating about BBDB in Japan, China, Denmark, Ireland, Korea and India. Masuda (1986) proposed BBDB and carried out the tank test. He showed that BBDB has the advantage that the primary conversion performance is better than other floating type devises, and the primary conversion efficiency of BBDB with the backward facing duct for the wave direction is larger than that with front facing duct for the wave direction in waves. Masuda et al. (1993) performed tank test for the various BBDB hull configuration to investigate of primary conversion performance.
