Improving the hydrodynamic efficiency of an offshore OWC wave energy converter through changes to the submerged depth of the OWC front face

Offshore oscillating water column (OWC) device is a renewable wave energy conversion (WEC) device that is promising to extract ocean wave energy through the waves-OWC chamber hydrodynamic interactions. A good understanding of these interactions is essential for the design and optimization processes. This paper uses a 2D fully nonlinear Computational Fluid Dynamics (CFD) model solving the Reynolds–Averaged Navier–Stokes equations to investigate the hydrodynamics of an offshore OWC-WEC device. The model was previously validated in good agreement against experimental results. Utilizing the CFD model, an extensive campaign of numerical tests is performed in order to uncover the relation between a wide range of incoming wave heights and the OWC front wall draft (lip submergence). The resulting impact on the device overall hydrodynamic efficiency, reflection and transmission coefficients are analysed over eleven wave periods. The key finding is that the maximum overall hydrodynamic efficiency is achieved when the submergence of the OWC front lip is equal to the incoming wave height. Also, increasing wave height improves the device efficiency, provided the ratio of maximum wave height to lip submergence is around unity.