Influences of wave resonance on hydrodynamic efficiency and loading of an OWC array under oblique waves

In this paper, a semi-analytical solution was derived from the linear potential flow theory using the matching eigenfunction method to investigate hydrodynamic characteristics of a rectangular oscillating water column (OWC) array under oblique waves. The theoretical results indicate that the sloshing resonance in the alongshore direction varies with the incident wave angle significantly. The presence of the along-shore sloshing resonance decreases the hydrodynamic efficiency and increases the wave reflection. The critical wavenumber kc at which the along-shore sloshing resonance occurs is identified as a key controlling factor of the performance of the OWC array. It is dependent on the chamber length in the along-shore direction. The peak efficiency occurs at the lower frequency for the larger incident wave angle. To our knowledge, this study provides the first theoretical evidence that the peak wave loading of the OWC array is triggered by the along-shore resonance under oblique wave action. Our theory confirms that the optimum coastal protection can be achieved by the peak efficiency of the OWC array in the frequency region of the piston resonance of the OWC.

Automated summary

This study derived a semi-analytical solution from linear potential flow theory to investigate hydrodynamic characteristics of a rectangular oscillating water column array under oblique waves. The presence of along-shore sloshing resonance was found to decrease hydrodynamic efficiency and increase wave reflection, with the critical wavenumber being dependent on chamber length. Peak efficiency was observed at lower frequencies for larger incident wave angles, indicating that optimum coastal protection can be achieved by maximizing efficiency in the piston resonance frequency region.