Theoretical investigation of hydrodynamic performance of multi-resonant OWC breakwater array

Abstract

In this paper, we theoretically investigate a multi-resonant oscillating water column (OWC) breakwater array. Based on linear potential flow theory, an extension of semi-analytical solution for wave interaction with periodic OWCs was developed for periodic OWCs with arbitrary chamber number. Both the diffraction and radiation problem for periodic multi-chamber OWCs are solved and verified using Haskind relation and wave energy flux conservation law. Parametrical analysis was conducted to examine the hydrodynamic characteristics of the present OWC breakwater system. Results indicate that multiple resonance of OWCs in piston mode led to multiple peaks of hydrodynamic efficiency, therefore broaden the effective frequency bandwidth with significant wave power absorption and coastal protection capability. However, the resonance of OWCs in sloshing mode in along-shore direction significantly weakens the wave power extraction. The triggering of the sloshing mode resonance mainly depends on the along-shore length of OWC unit and the incident wave angle. For larger along-shore OWC unit length (2l > h, within the present calculations), the effective frequency bandwidth is significantly influenced by the incident wave angle. Notably, when the incident wave angle exceeds π/4, the effective bandwidth decreases by half approximately. However, for narrower lengths (2l < h), the hydrodynamic performance of the OWC array demonstrates reduced sensitivity to the variations of the incident wave angle.