Numerical study on the hydrodynamic performance of a coupled oscillating buoy-oscillating water column wave energy converter

This study proposes a novel hybrid wave energy converter (WEC) that integrates a system of counter-oscillating buoys (OBs) into a land-based oscillating water column chamber (OWC). This design specifically aims to enhance the power capture efficiency of the device for short-period waves, particularly those near the sloshing resonant period. A two-dimensional computational fluid dynamics model was developed using the software program OpenFOAM to investigate the effects of the buoy damping coefficient, buoy degrees of freedom motion, OB geometry, and front-wall draft on integrated system performance. The numerical model was comprehensively verified and validated through grid independence studies and experimental data comparisons. The results demonstrate significant hydrodynamic coupling between the buoys and the OWC; the buoys capture energy independently of the OWC and effectively enhance the chamber pressure response, overcoming the efficiency diminution of conventional OWCs at specific frequency bands. Different buoy geometries lead to distinct energy distribution characteristics. The hybrid wave energy converter incorporating wedge-shaped buoys achieves 38.2% higher efficiency than the stand-alone OWC. Nonlinear spectral analyses identify the physical mechanism behind an anomalous reflection coefficient reduction observed under specific wave conditions, attributing this effect to the trapping and dissipation of high-frequency harmonics within the chamber. • Novel hybrid OWC-OB system enhances wave energy capture in short-period waves. • Identical damping coefficients for dual buoys enable maximum overall system efficiency. • Different buoy geometries effectuate distinct energy distribution and vortex dynamics. • Trapped high-frequency harmonics in the chamber reduce wave reflection coefficient. • Hybrid system maintains superior performance over standalone OWC in irregular waves.