Numerical investigation of flow dynamics and energy dissipation over irregular coastal beds using RANS–VOF modeling

This study investigates fluid–structure interactions over three distinct irregular seabed geometries: vertical, triangular and curved parabolic profiles through high-resolution numerical simulations. The incompressible, unsteady flow was modeled via the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the volume of fluid (VOF) method and the realizable k–Formula: see text turbulence model to capture free-surface evolution and turbulence dynamics. Results reveal that wave-induced pressure, force and energy dissipation are strongly influenced by seabed geometry. The vertical plate experienced the highest pressures and forces due to impulsive wave impact and reflection, while the triangular slope facilitated gradual energy dissipation, reducing hydrodynamic loading. The curved profile showed the lowest force and pressure magnitudes and the highest energy dissipation efficiency (67%), attributed to its smooth flow guidance and reduced reflection. Flow field analysis highlighted distinct vortex formation patterns, with the vertical step producing strong coherent vortices, the triangular slope exhibiting diffuse turbulence and the curved profile generating high surface vorticity and jet-induced run-up. Turbulent kinetic energy (TKE) distribution indicated that the curved seabed effectively minimized bed-level turbulence and potential scour, enhancing flow stability. Overall, the study provides comprehensive insights into the influence of seabed geometry on wave hydrodynamics and offers practical guidance for optimizing coastal and offshore structural designs to improve energy dissipation and reduce wave-induced loads.