Enhancing wave power focus with periodic wave-guiding walls in a three-unit oscillating water column array integrated with a vertical breakwater

Maximizing the utilization of marine infrastructure, while optimizing its form and arrangement, facilitates the deep integration and innovative development of the marine engineering sector and wave energy generation field. This study demonstrates the proof-of-concept of a linear arrayed structure composed of three identical cylindrical oscillating water column (OWC) sub-units integrated into a vertical breakwater with periodic wave-guiding walls. Acting as wave focusing structures, these walls enhance complex wave reflection and interference phenomena, leading to concentrated wave energy transmission. The hydrodynamic efficiency of an isolated OWC and a three-unit OWC arrayed structure, both embedded into a vertical breakwater with and without the wave-guiding walls, was compared. The effects of transverse spacing - which influences the geometrical scale of the periodic wave-guiding walls - and wave nonlinearity on wave power extraction performance were investigated. The results indicate several key findings. Firstly, for an isolated OWC with the wave-guiding walls, the maximum hydrodynamic efficiency at the resonant frequency increased from 82.8% to 189.78%, with significant enhancement in the short-wave regime and a shift in the resonance frequency. Secondly, for the three-unit OWC arrayed structure, wave-guiding walls significantly improved wave energy conversion efficiency, with the overall efficiency growth rate exceeding 25% across all tested wave conditions. Furthermore, adjusting the transverse spacing to three times the width of the OWC chambers resulted in up to a 400% increase in overall hydrodynamic efficiency, with peak efficiency reaching 650%. Additionally, wave height minimally affected the resonant frequency and hydrodynamic efficiency curves, but increasing wave height decreased efficiency for each sub-unit across all wave frequencies. Finally, compared to parabolic reflector walls, the wave-guiding walls broadened the efficient frequency band, with average hydrodynamic efficiency exceeding 0.5 across the entire tested range. These results highlight the potential of wave-guiding walls in enhancing wave energy capture efficiency in OWC structures integrated into vertical breakwaters.