Numerical Investigation of Still-Water Depth Effects on Tsunami-Like Bore Hydrodynamics and Loading on Structural Arrays Over Varying Bathymetry

Mirghafouri, S., and Farhadzadeh, A., 2026. Numerical investigation of still-water depth effects on tsunami-like bore hydrodynamics and loading on structural arrays over varying bathymetry. Journal of Coastal Research, 42(5), 826–852. Charlotte (North Carolina), ISSN 0749-0208. This study investigated the influence of downstream still-water depth on dam-break bore-induced local hydrodynamics and loading on an array of structures on a berm. Numerical simulations were conducted using OpenFOAM. The computational fluid dynamics (CFD) model employing a large eddy simulation turbulence closure scheme was validated against experimental data obtained from dam-break tests. These experiments involved two distinct structural configurations positioned on a berm at the end of a sloping beach. The validated CFD model was used to examine how variation in downstream still-water depth affects bore evolution, local hydrodynamics, and force on the structures. The results demonstrate that local hydrodynamics are highly sensitive to variations in downstream water depth, a factor that remains underexplored in literature. Under dry-berm conditions, where the downstream still-water levels were below the berm elevation, the bore exhibited peak velocities, intense vorticity, and maximum runup heights on the structures. Conversely, the highest pressure and total force on the front-row structures were observed under an intermediate-depth wet-berm scenario. Although forces on the back-row structures increased with greater downstream water depth, they remained significantly lower than those on the front-row structures. The study evaluated three force estimation methods, the convective momentum flux approach, the steady-state momentum flux approach, and the American Society of Civil Engineers (ASCE) 7-16 formulation, by comparing their predictions with the computed hydrodynamic forces acting on the front-row structures. While all three methods provided reasonable estimates of force magnitude, they showed limitations in accurately capturing the variation of forces with downstream water depth. Among the approaches, the convective momentum flux method more effectively reproduced the observed force trends across different tailwater conditions and resulted in lower average prediction errors. The ASCE 7-16 formulation yielded consistently more conservative force estimates and captured the overall trend more accurately than the steady-state momentum flux approach.