A floating-type wave energy converter, Backward Bent Duct Buoy (BBDB) was analyzed its hydrodynamic performance by numerical and experimental methods. A two-dimensional time-domain, fully nonlinear numerical wave tank (NWT) technique based on potential theory and the mixed Eulerian-Lagrangian (MEL) approach was used to simulate the wave-body interaction of the BBDB system. The nonlinear freesurface inside the chamber was specially treated to represent the viscous effect of fluctuating water column due to the shape of body. The pneumatic pressure of the time-varying airflow velocity in the chamber was also considered. An experiment on the system was carried out to verify the numerical results. The NWT simulations with a tuned viscous damping coefficient were found to be correlated reasonably well with experimental values for various incident wave frequencies.
Ocean wave energy as one of the key renewable energy sources has been the interesting subject of researchers and scientists since the 19th century. Over 1000 patented wave energy converters have been developed and tested for last several decades. There are only nine basic ideas on which these techniques are based (McCormick, 2007). One of the most promising concepts is the oscillating water column (OWC), which based on the pneumatic power take-off achieved by using specially designed turbines such as the Wells turbine, Impulse turbine and Denniss-Auld turbine. The OWC concept as the first commercially available wave energy conversion system was first proposed by Masuda (1971), and was subsequently experimented through field tests by Hotta et al. (1988) and Washio et al. (2000). Several commercial-level fixed-type OWC plants have been constructed recently and successfully operated (e.g. Heath et al., 2000). For a floating-type OWC system, the Backward Bent Duct Buoy (BBDB) device with pneumatic air chamber is very famous device which was originally proposed and experimented by Masuda et al. (1987).
