Hydraulic performance of oscillating water column structures as anti-reflection devices to reduce harbour agitation

This paper aims at assessing the effectiveness of an oscillating water column device, generally conceived and studied as a wave energy converter, as an anti-reflective system to be integrated into vertical wall harbour structures. The wave-structure interaction is studied with simulations carried out in a numerical wave tank, implemented in the computational fluid dynamics environment OpenFOAM®. Reflected and radiated wave components are decomposed and the interaction between these components is studied. A quasi-standing wave field is present in front of the structure. The effect of design parameters and hydrodynamic conditions on the reflection properties and on the wave field in front of the structure is discussed. Results are analysed in terms of dimensionless parameters and original empirical formulae to predict the wave reflection are given. Minimum reflection coefficients (including both properly reflected and radiated waves) around 15% are found, suggesting that the OWC could efficiently be used to reduce wave agitation in front of vertical wall harbour structures. The reflection coefficient is primarily influenced by the ratio of the camber length W to the incident wavelength L, with minimum values for W/L = 0.1–0.17. Minimum values of the ratio of the quasi-antinode height to the incident wave height around 1.1 are found.