Experimental study on a back-bent duct buoy oscillating water column device in various degrees of freedom.

The back-bent duct buoy (BBDB) is a floating oscillating water column wave energy converter, which has good environmental suitability, survivability, energy-harvesting capability, and smaller mooring forces. In this study, a BBDB OWC model with a generic shape was designed and tested using regular wave scenarios in a wave flume. Four combinations of the degree of freedom (DOF) were employed in the experimental tests: the zero DOF (fixed, ZDOF) mode, the two DOFs (heaving and pitching, TDOFs) mode, and the single DOF (only pitching or heaving, SDOF-P and SDOF-H) modes. The time histories of key performance parameters, kinematic responses, hydrodynamic, aerodynamic, and energy-harvesting performances were reported and analyzed. The resonance migrations of the air pressure and pneumatic power were observed for different DOF conditions. In addition, the pitching and heaving motions are found to have positive and negative effects on the energy-harvesting performance of the BBDB model. The peak values of capture width ratios for the ZDOF, SDOF-P, SDOF-H and TDOFs conditions are 0.57, 0.51, 0.10, and 0.26, while the average values are 0.19, 0.19, 0.03, and 0.11, respectively. [ABSTRACT FROM AUTHOR]