Numerical Investigation on the Hydrodynamics of Vertical Seawalls Defended by a Submerged Breakwater

Submerged breakwaters are emerging as a viable solution to mitigate the adverse effects of increased wave action on coastal structures such as seawalls. This study undertook a comprehensive and rigorous numerical investigation to illustrate the hydrodynamic performance of a nonporous submerged breakwater positioned at varying distances seaward of the seawall under various wave conditions. An open-source computational fluid dynamics-based numerical model, REEF3D, which solves the Reynolds-Averaged Navier–Stokes equations using the finite difference method, was used for the numerical modeling of wave–structure interaction. The numerical model was meticulously validated, ensuring its accuracy and reliability, with experiments conducted in a wave flume using the seawall model. The validated model was then applied to simulate wave interaction between the seawall and submerged breakwater for different pool lengths subjected to regular waves. The study primarily focused on assessing wave elevation in proximity to the seawall, wave reflection characteristics, and hydrodynamic pressures exerted on the seawall when the seawall is defended by a submerged breakwater. The numerical model also analyzed the spatial and temporal distribution of free surface elevation and generation of higher harmonics along the numerical wave tank. This thorough approach ensures a deeper understanding of the complex wave–structure interaction processes within the pool zone. This study found that incorporating a submerged breakwater seaward of the seawall may not consistently result in wave attenuation. The results showed that reduction in free surface elevations and pressures follows a nonmonotonic trend with variations in the pool length. Further, the influence of pool length is not significant when interpreting the maximum pressure reduction for varying pool lengths. These findings have significant implications for the design and implementation of coastal structures.