Hydrodynamic performance of dual-chamber Oscillating Water Column array under oblique waves

A multiple Oscillating Water Column (OWC) device may provide better wave absorption over a wider frequency bandwidth than a single-chamber OWC due to multiple resonances. The scattering and radiation of three-dimensional oblique waves by an array of periodic dual-chamber OWCs are considered here along a coastal cliff. A semi-analytical model was developed based on potential flow theory and matching eigenfunction method to investigate the oblique wave interaction with a dual-chamber OWC array system. The velocity singularity at the tip of a chamber wall is resolved by introducing the Galerkin technique to accelerate the convergence. The semi-analytical solution is verified by the Haskind relation and energy conservation law. Hydrodynamics of the proposed system and the influence of wave and geometric parameters were investigated. Theoretical results indicate that a dual-chamber OWC array has a broader capture bandwidth than a single-chamber OWC array for both normal and oblique waves. The presence of the along-shore and cross-shore sloshing resonance is theoretically confirmed in each subchamber of OWC unit, which decreases the hydrodynamic efficiency and increases the wave reflection drastically. Although the wave loading on the chamber wall decreases with increasing incident wave angle theta, the wave loading on chamber/partition wall may increase sharply due to sloshing resonance at critical frequency k(c). To our knowledge, this is the first attempt to investigate the hydrodynamics of dual-chamber OWC array under oblique waves. The present theoretical results indicate the potential risks of structural damage and total wave reflection due to sloshing resonance, which should be an important design consideration. Published under an exclusive license by AIP Publishing.

Automated summary

A multiple Oscillating Water Column (OWC) device can absorb waves over a wider frequency range than a single-chamber OWC due to multiple resonances. In this study, a semi-analytical model based on potential flow theory and matching eigenfunction method was developed to investigate the interaction between oblique waves and a dual-chamber OWC array system. The theoretical results reveal that a dual-chamber OWC array has a broader capture bandwidth than a single-chamber OWC array for both normal and oblique waves. Additionally, the presence of along-shore and cross-shore sloshing resonance in each subchamber of the OWC unit is confirmed, which decreases the hydrodynamic efficiency and increases wave reflection.