Hydrodynamic and energy-harvesting performance of a BBDB-OWC device in irregular waves: An experimental study

The back-bent duct buoy (BBDB) can be used as a floating oscillating water column (OWC) wave energy converter, showing its potential and reliability in most previous prototype sea trials. In this study, an experimental test on a generic BBDB OWC model was conducted in a wave flume using irregular wave scenarios. By using a specific mechanism, the degree-of-freedom (DOF) of the model can be preset in four modes: the ZDOF (the model is fixed with zero DOF) mode, the TDOFs mode (the model conducts the pitching and heaving motions with two DOFs), the SDOF-P mode (the model conducts the pitching motion with the single DOF), and the SDOF-H mode (the model conducts the heaving motion with the single DOF). The kinematic, hydrodynamic, and aerodynamic responses and energy-harvesting performances of the BBDB model were presented and analyzed. It was found that the pitching and heaving motions made positive and negative contributions to wave power capturing of the model, resulting in a moderate energy-harvesting performance for the TDOFs mode. Furthermore, the analysis indicated that strengthening the pitching motion and restraining the heaving motion will benefit the wave energy conversion of the BBDB device.