Langmuir Circulation in Inner-Shelf Tidal Currents: A Reynolds-Averaged Navier-Stokes Approach

While field measurements and numerical simulations have previously demonstrated the presence of full-depth Langmuir Supercells (LS) in shallow coastal shelves, the computational demands of capturing LS through Large Eddy Simulation (LES) remain high, especially at the high Reynolds numbers characteristic of geophysical flows. In this study, we present a computationally efficient Reynolds-averaged Navier-Stokes (RANS) approach to model LS, incorporating the Craik-Leibovich (C-L) vortex force to parameterize the wave-current interaction responsible for Langmuir Circulation (LC). This method utilizes a modified k-epsilon turbulence closure model, adapted to account for the unique turbulent kinetic energy generation by Stokes drift shear and the non-local transport effects induced by LS. Additionally, it integrates tidal forcing into the RANS framework to explore how tidal flows, combined with misaligned wind and waves, influence LS strength and structure in coastal oceans. The proposed RANS methodology is validated against LES based studies and field observations, demonstrating its effectiveness in capturing the key dynamics of LS while significantly reducing computational costs. This approach provides a viable alternative for simulating LS in coastal ocean models, enabling broader exploration of their dynamics and impact on sediment transport, nutrient distribution, and other critical oceanic processes.