Hydrodynamic analysis of a multi-chamber OWC array over coral reef bathymetry

The oscillating water column (OWC) technology presents a promising solution for wave energy capture. Multi-chamber OWCs have gained attention due to their excellent energy capture performance. This paper evaluates the hydrodynamic performance of a shore-based multi-chamber OWC array over coral reef bathymetry. A semi-analytical model is developed based on linear potential flow theory, using the matched eigenfunction expansion method to solve the interaction between water waves and the multi-chamber OWC array over variable bathymetry. The Haskind relation and the wave energy flux conservation law are used to validate the semi-analytical model. Furthermore, the semi-analytical model is validated against published numerical data. Parametrical investigations are conducted to explore the hydrodynamic performance of the OWC array in the presence of coral reef bathymetry. Results show that multi-chamber OWCs broaden the effective bandwidth compared to single-chamber OWCs. Moreover, the overall hydrodynamic efficiency converges when the number of OWC chambers increases to eight. An OWC configuration with a gradually increasing wall draft along the wave propagation direction provides better wave energy extraction performance. The strong wave reflection phenomena (see Fig. 17) triggered by the caisson array results in a sharp drop in hydrodynamic efficiency and a narrowing of the effective frequency bandwidth. This bandwidth narrows further with an increase in the incident wave angle. In addition, wave resonance (see Fig. 19) over variable bathymetry (e.g., reef flat) and its influence on wave power extraction performance of multi-chamber OWC array are illustrated.