The hydrodynamic performance of the wave power extraction of an innovative modified breakwater-integrated Oscillating Water Column (OWC) wave energy converter is both numerically and experimentally presented in this study. The modified OWC device comprises a non-conventional perforated wall in front of a typical OWC chamber. The air-water two-fluid model, considering the fluid compressibility involved in FLOW-3D solver, is employed for the numerical simulations of the hydrodynamic characteristics of the OWC devices. The numerical simulations of the hydrodynamic performance of the OWC device are first validated by the experimental measurements with a scaled model. The effects of the geometry of the OWC chamber on the hydrodynamic efficiency are then discussed by numerical simulations using a full-scale OWC device under regular waves. The numerical and experimental results show that the present modified device can form a U-type flow pattern by the oscillating water column, thus developing better performance in extracting pneumatic power, when compared with the typical OWC device which does not have the perforated front wall. The results indicate that the present modified OWC device can not only promote the efficiency of the pneumatic power extraction, but can also reduce the wave force acting on the structure.

Detached breakwaters are widely used for shore protection. The planforms of tombolos or salients behind structures have also been used to provide a recreational and sustainable coastal environment. In this study, the comprehensive XBeach model was used to numerically simulate the evolution of wave transformation, nearshore current, and morphological changes in tombolo planforms behind detached breakwaters. Given various gap spacings between consecutive breakwaters, the numerical results indicated that both equilibrium bay-shaped shorelines and bottom profiles form in the lee of detached breakwaters after long-term persistent wave action. These equilibrium shorelines and bottom profiles were verified using well-known empirical formulas. Post-wave-action retreat displacement to the initial shoreline was analyzed, and an empirical relationship was proposed for predicting the equilibrium bay-shaped shoreline. By associating the empirical formula with a parabolic bay-shape equation, some actual beaches were evaluated to validate the predictions of equilibrium shorelines behind detached breakwaters. In conclusion, to appropriately plan the layouts of breakwaters, bay-shaped shorelines of tombolo planforms in the lee of detached breakwaters can be predicted at the design stage by using the proposed relationship.