Impact of Crownwall Shape on Wave Forces and Overtopping at Vertical Breakwaters

Overhanging parapets are commonly adopted in vertical breakwaters to reduce wave overtopping. However, previous studies have shown that these structures may also be subjected to significant impulsive loads associated with the Confined-Crest Impact (C-CI) phenomenon. While the loading mechanisms of conventional recurved parapets have been extensively investigated, the influence of alternative overhanging geometries on both wave loading and overtopping reduction remains poorly understood. This study investigates the hydraulic efficiency and wave loading on rectilinear, recurved, and recurved crownwall under non-breaking wave conditions by means of Reynolds-Averaged Navier-Stokes (RANS) simulations coupled with a Volume of Fluid (VOF) approach. The results show that parapet geometry strongly influences both dynamic/impulsive wave loading and overtopping volumes. The recurved crownwall achieves the greatest overtopping reduction but also the highest force amplification. Conversely, the recurved parapet produces the lowest impulsive loads among the tested overhanging geometries, at the expense of hydraulic efficiency, although these loads remain higher than those experienced by the reference vertical parapet. These findings reveal a trade-off between overtopping mitigation and structural loading, indicating that the most hydraulically effective geometry is not necessarily the most structurally advantageous.