Phase-tuned wave focusing by dual-parabolic breakwaters with a submerged secondary element

Integrating wave energy converters with coastal breakwaters can reduce infrastructure costs and improve the use of nearshore wave energy. This study proposes a dual-parabolic breakwater confruration, coupling a surface-piercing primary parabolic concentrator with a submerged secondary parabolic structure, to realise phase-modulated wave focusing. A second-order three-dimensional higher-order boundary element model is used, with its mesh convergence verified numerically and the single-breakwater baseline validated against wave-basin experiments. The secondary wall produces delayed scattered waves that interact with the primary focused field. Consequently, focal amplification depends on multi-path superposition and exhibits clear frequency selectivity. Varying the distance between the two focal points alternates constructive and destructive interference and shifts the optimal confruration predictably. The secondary-wall chord length also has a non-monotonic effect because it changes the effective phase of the scattered waves. These findings establish a phase-based mechanism for tuning dual-breakwater focusing and provide guidance for integrating wave energy systems with coastal structures. Xiangyu Zhang and colleagues investigate phase-tuned wave focusing by a dual-parabolic breakwater using a second-order three-dimensional boundary-element model. The submerged secondary breakwater generates delayed scattered waves whose phase can be tuned to enhance focal amplification across target wave conditions.