Energy absorption and wave blocking of hybrid system with a backward bent duct buoy and a floating breakwater

A hybrid system is proposed, where a floating breakwater (FB) is positioned downstream of the backward bent duct buoy (BBDB) oscillating water column (OWC) wave energy converter (WEC). The efficient wave energy absorption and wave blocking performance are achieved by the system. The coupling mathematical model of the BBDB device and FB is established based on the potential flow theory, which allows the BBDB device to move in the direction of surge, heave, and pitch. The results show that the FB downstream arrangement can improve the absorption performance of the BBDB device, and the wave period with an absorption efficiency exceeding 0.8 can be widened by 69 %. The transmission coefficient of the hybrid system is 60 % smaller than that of the isolated FB. By adjusting the distance between the BBDB device and FB, the transmission coefficient can be maintained below 0.1 when the period is less than 8.2 s. Increasing the stiffness of the mooring system in the pitch direction of the BBDB device can help in reducing the transmission coefficient when the wave period is between 9-10 s when the pitch motion is fully restricted, the transmission coefficient is less than 0.41 during this period.