A Reynolds-averaged methodology for simulating Langmuir cells in the coastal ocean *

Langmuir turbulence in the upper ocean is driven by winds and waves and is characterized by Langmuir cells (LCs), parallel counter rotating vortices roughly aligned in the wind direction. In the coastal ocean, the largest LCs can span the full depth of the water column becoming more coherent and persistent than LCs in the upper ocean mixed layer. Traditionally, flows with LCs are computed via either (1) large-eddy simulation (LES) in which a range of the Langmuir turbulence (or cells) is resolved or with (2) Reynolds averaging in which none of the Langmuir scales are resolved and the effect of the Langmuir turbulence is accounted for through the turbulence model. A new solution strategy based on Reynolds averaging is introduced, relying on the coherency and persistence of full-depth LCs. Here these cells are treated as a secondary component to the wind and/or pressure gradient-driven primary flow. As such, the Reynolds-averaged governing flow equations and the mesh are designed to resolve both the primary flow and the full-depth LCs with the turbulence model accounting for the smaller Langmuir scales. The resolved LCs and associated statistics will be compared with their counterparts in LES.