Breaking wave impact on perforated caisson breakwaters: A numerical investigation

Abstract

With the use of a pressure-based compressible flow solver, the issue of breaking wave impact on perforated caisson breakwaters (PCBs) is comprehensively investigated. The wave profile at the moment of impact, the pressure induced by breaking waves, and the wave−structure interaction process, are detailed. Three key findings are concluded: (i) air is inevitably trapped in the impact process because the water inside the wave absorption chamber (WAC) leaks through the perforated wall and then drops into the water in front of the PCB, causing water aeration; (ii) the upward pressure inside the opening above the still water level is close or even greater than the pressure on the perforated wall, and this upward pressure might be directly scaled as per the Froude law because no air is trapped; (iii) most of the commonly used empirical formulae fail to provide a reasonable prediction of the maximum pressure and force on the PCB induced by breaking waves. Finally, a comparatively large wall porosity, such as 0.4, is recommended in the design of PCBs because it is beneficial to diminishing the maximum pressure on the perforated wall and inside the opening, as well as the maximum horizontal force on the PCB.