Influence of vertical breakwater wall roughness on wave-induced overtopping: A CFD-based study

In this study, we analyzed the wave dynamics in a nearshore region protected by a vertical breakwater through computational fluid dynamics (CFD) simulations. The focus was placed on evaluating the role of vertical wall roughness in influencing wave energy dissipation and overtopping behavior when waves encounter coastal structures. Four wall conditions were modeled with varying roughness coefficients: A smooth wall (NR = 0.0), and progressively rougher walls denoted as WR1 (0.5), WR2 (0.75), and WR3 (1.0). These cases were designed to systematically assess how increased surface roughness affects the hydrodynamic response of waves in front of and behind the breakwater. The simulation results demonstrated a clear trend: As wall roughness increased, the overtopping water depth consistently decreased. Specifically, the overtopping values were 0.083 m for the smooth wall (NR), followed by 0.082 m, 0.081 m, and 0.0719 m for WR1, WR2, and WR3, respectively. This suggests that increased wall roughness enhances wave energy dissipation, thereby reducing the volume of water overtopping the structure. These findings highlight the critical role of structural surface characteristics in coastal defense design. Incorporating surface roughness into vertical breakwater modeling can contribute to more effective wave energy attenuation, potentially improving the resilience and performance of coastal protection systems under wave impact.