Reynolds-averaged Simulation of Langmuir Turbulence in the Costal Ocean

Langmuir turbulence in the costal ocean is driven by winds and waves and is characterized by Langmuir cells (LCs) that can span the full depth of unstratified water columns. A solution strategy based on Reynolds averaging is introduced, relying on the coherency and persistence of full-depth LCs. Here the full-depth cells are treated as a secondary component to the wind and/or pressure gradient-driven primary flow. The resolved LCs and associated statistics will be compared with their counterparts in large-eddy simulation (LES). The comparison shows that the Reynolds-averaged approach can reproduce cell meandering and merging (i.e. the so called Y junctions), a requisite for capturing the proper crosswind scales of the LCs. The merging occurs less frequently over time as the cells grow after being spun from rest. The Reynolds-averaged approach will be extended to simulations involving a coastal boundary through coupling with a wave model predicting the Stokes drift velocity of the surface waves. Studies based on this approach will be presented investigating the impact of the costal shore and wave direction on the structure and intensity of the LCs in a surf-shelf transition zone. The impact of LCs on cross-shore mass transport will be investigated via a passive tracer.