A Numerical Study of Swash Driven by a Plunging Solitary Wave Over a Permeable Sandy Beach

Swash zone flows are characterized by continuously varying free surface elevation and intermittent wetting and drying. These transient flow features induce upward/downward pore pressure gradients during uprush/backwash processes (Sumer et al., 2011, JGR) that may affect sediment stability. Understanding porous media hydrodynamics, infiltration/exfiltration processes, and resulting pressure responses is a crucial step toward improved coastal morphological modeling. A numerical model capable of resolving the entire water column including a permeable sand layer is essential. Recently, an open-source free surface resolving Reynolds-averaged Eulerian two-phase sediment transport model, SedWaveFoam (Kim et al., 2018, JGR: Oceans), was developed. SedWaveFoam concurrently resolves the free surface wave field, bottom boundary layer, and sediment transport processes in a unified numerical modeling framework based on OpenFOAM. The numerical model successfully reproduces sheet flow under monochromatic nonbreaking (Kim et al., 2018, JGR: Oceans) and breaking surface waves (Kim et al., 2019, Coast. Eng.). In this study, SedWaveFoam is modified with a fixed sediment bed and applied to a plunging solitary wave on a permeable sandy beach. Preliminary results show modeled free surface elevation agrees well with measured data (Sumer et al., 2011, JGR) while the upward pore pressure gradient imparted by bore arrival is accurate to within a factor of two. The modified SedWaveFoam is validated and used to systematically analyze the effects of pore pressure gradients and wave-breaking-induced turbulence on sediment transport.