Hydrodynamic performance of a multifunctional oscillating water column-breakwater system with a porous plate

Combining an oscillating water column (OWC) device with an offshore stationary breakwater presents a promising approach to balance wave energy conversion and wave attenuation. However, enhancing its safety while maintaining its original performance remains a key challenge. This study innovatively proposes a multifunctional OWC-breakwater system with a porous plate being mounted in front of the structure to dissipate high-frequency wave energy. The hydrodynamic performance of this integrated system is systematically investigated through physical experiments and numerical simulations. Its performance is compared against the conventional OWC- and box-type breakwaters. The results indicate that under all considered wave conditions, the integration of the porous plate significantly decreases the wave force on the seaward surface of the front wall, thereby reducing the overall structural load. This effect is particularly pronounced under strong nonlinear wave actions. Meanwhile, the hydrodynamic efficiency is slightly enhanced in low-frequency conditions. This improvement is attributed to the porous plate enabling more first-order wave energy in front of the breakwater to be absorbed by the chamber rather than being transferred to higher-order components. In the high-frequency region, the reflection coefficient is effectively reduced, and the dissipated energy ratio is evidently increased to twice its original level. These findings highlight the superiority of the integrated system in terms of the viability in energy conversion and the performance in wave dissipation. The study opens a new avenue for innovative designs of integrated wave renewable and offshore defense system that can potentially benefit other related engineering applications.