3D numerical simulation of wave transmission for low-crested and submerged breakwaters

Low-crested and submerged breakwaters, serving as one of the coastal defensive structures, are usually used to dissipate wave energy and help reduce wave impacts on coastal infrastructures and communities especially during extreme weather events, such as hurricanes or tsunamis. Many recent post disaster surveys indicated that breakwaters did not perform as designed during some extreme weather events. The performance of the breakwaters subjected to strong waves is still not clear especially when the breakwaters turn into the submerged condition. Meanwhile, many researches on the breakwaters are usually carried out in a two-dimensional wave flume either experimentally or numerically. However, the incident wave could impact the breakwaters from any directions instead of only from the head-on direction, which should be a three-dimensional physical process of wave and breakwater interactions. Therefore, it is essential to conduct a three-dimensional numerical study to investigate the breakwater performance in reducing the transmitted wave energy behind it and compare the results with those from a two-dimensional study. This study is to investigate the effect of three-dimensional interactions of obliquely incident waves and breakwaters on wave potential energy reduction based on the proposed energy transmission coefficient. Computational fluid dynamics (CFD) simulations are carried out in OpenFOAM to simulate the interactions between the wave and breakwater using a three-dimensional Reynolds averaged Navier-Stokes (BANS) model together with the k-omega SST turbulence model. Two validation studies are performed to validate the applicability of the proposed numerical model in two-dimensional and three-dimensional numerical simulations. Sensitivity analyses are performed to investigate the effect of different parameters associated with breakwater geometries and incident wave properties on a two-dimensional submerged breakwater performance in reducing the transmitted wave height. The effects of incident wave angle on the transmitted wave energy reduction for a three-dimensional submerged and surface breakwater are then investigated and compared with the two-dimensional simulation results. The numerical studies indicate that a three-dimensional simulation is more appropriate to describe a breakwater behavior in the real-world scenario.