Numerical evidence of contrasting hydrodynamic responses of concave and convex breakwaters

This study numerically investigates the interaction of solitary waves with arc-shaped breakwaters using the non-hydrostatic shallow water equation model REEF3D::SFLOW. Large-domain simulations are conducted to compare the hydrodynamic responses of concave arc-shaped breakwater (CC-ASBW) and convex arc-shaped breakwater (CX-ASBW) with those of a straight vertical-wall breakwater (VBW). Model validation was carried out using analytical solutions, laboratory measurements, and previously published numerical data, confirming its predictive accuracy. The simulations resolve free-surface evolution, diffraction patterns, and vortex dynamics, supported by detailed analyses of circulation, core vorticity, vortex radius, and trajectory. The results show that the concave geometry concentrates energy toward the central region, generating strong wave focusing, higher normalized free-surface elevation, and pronounced reflection along the centerline. Conversely, the convex geometry disperses energy laterally, lowering reflection near the center and providing improved sheltering behind the structure. The VBW exhibits nearly uniform reflection along its face but limited energy dissipation in the lee. Quantitative analysis confirms that geometric curvature critically governs energy redistribution and vortex behavior, with concave curvature intensifying local reflection and coherent vortices, while convex curvature weakens circulation and reduces transmission. These findings establish the contrasting hydrodynamic behavior of concave and convex geometries and provide practical guidance for curvature-aware breakwater design.