Wave interaction with two-dimensional submerged perforated thin-plate structures: Effects of structure shape

Perforated thin-plate structures, which can effectively dissipate wave energy and also serve as base structures for growing corals in nature-based solutions to shore protection problems, can be promising alternatives to traditional rubble-mound breakwaters for shore protection. The growth of corals may be affected by the geometrical shapes of the base structures. This study investigates wave interaction with one or multiple submerged perforated thin-plate structures, emphasizing effects of structure's shapes on wave transmission and wave loading. Using a multi-domain boundary element method (BEM) and a parameterization of the pressure drop across a perforated thin plate, six cross-sectional shapes that belong to the following four types are considered for different ratios of structure height to water depth: rectangular, trapezoidal, triangular, and semi-circular shapes. For the purpose of verifying the BEM codes, an analytical solution was also developed for a single structure with a rectangular shape. The results show that for a given number of structures, the rectangular and trapezoidal shapes are more effective in reducing wave energy transmission, providing protection across a range of wave periods. The reduction of wave energy in the transmitted waves is controlled mainly by the energy dissipation into turbulence. Resonant reflection, found when multiple structures are used, can only slightly affect wave transmission in the frequency range of practical relevance. The wave loading on the structures for promising designs is studied. The results reported here are useful for marine biologists and coastal engineers to choose a suitable shape for the base structures for reducing wave energy and growing corals and geotechnical engineers to design foundations and anchoring schemes.