Deping Cao

Wave overtopping over coastal structures involves highly transient shallow flows characterized by strong free-surface deformation and intense turbulence generation. Although considerable research has focused on overtopping discharge and volume, the detailed kinematics and turbulence characteristics of overtopping flows remain insufficiently understood. In the present study, a two-phase wall-modeled large-eddy simulation approach implemented in OpenFOAM is applied to investigate wave overtopping flow over a seawall under regular wave conditions. The numerical model is rigorously validated against laboratory measurements, including overtopping layer thickness and high-speed particle image velocimetry velocity fields, demonstrating good agreement in terms of free-surface evolution and overtopping flow kinematics. The results reveal that the overtopping flow is strongly phase-dependent and dominated by the streamwise velocity component, with pronounced turbulent fluctuations concentrated near the free surface and the bed. The overtopping flow remains supercritical (Fr>1.5) near the leading edge of the seawall crest, while the Froude number gradually decreases downstream due to bed friction and turbulent energy dissipation. The bed shear stress is highly transient, with instantaneous peak values exceeding the time-averaged values by a factor of 3–7. The subgrid-scale turbulent kinetic energy (TKE) accounts for only 6.05% of the total TKE within the resolved flow domain, confirming that the dominant turbulent structures are well captured by the present mesh resolution. The TKE budget further reveals that production and turbulent transport are the dominant terms during the active overtopping phase, with peak production concentrated near the leading edge and within the bottom boundary layer.