Multi-phase simulation of gravel beach morphodynamics

This study applies an Eulerian–Eulerian multi-phase model to investigate sediment transport dynamics across a gravel beach subjected to regular waves. We numerically replicated a previously conducted full-scale experiment, achieving consistency between simulated and measured wave deformation, flow velocity, pore pressure, and morphological changes. The multi-phase model successfully reproduced observed phenomena, demonstrating berm formation for smaller waves and beach erosion for larger waves, aligning with findings from prior field studies. A sensitivity analysis reveals the substantial influence of the nonlinear drag component on berm formation, primarily through infiltration and exfiltration processes. Two dominant forces acting on sediment, namely drag and buoyancy, are studied. Drag emerges as the primary force governing sediment transport, exhibiting a strong correlation with depth-averaged flow velocity. The buoyancy, generated by plunging flow impacting the beach face, propels sediment landward in the bore front, coinciding with peak flow acceleration. Previous sediment transport models have empirically considered flow acceleration for gravel beach morphological evolution under waves. This study establishes a linkage between buoyancy, flow acceleration, and sediment transport rate in the bore front, offering valuable insights into the intricate interactions governing gravel beach dynamics. The findings contribute to our understanding of sediment transport mechanisms and hold implications for coastal engineering.