CMS-Flow:Subgrid Turbulence Model

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Eddy Viscosity

In CMS-Flow eddy viscosity is calculated as the sum of the kinematic viscosity νt0, the current-related eddy viscosity νc and the wave-related eddy viscosity νw

     νt=νt0+νc+νw

There are two options to calculate νc. The first is the Falconer (1980) equation given by


     νc=0.575Cb|U|h


where Cb is the bottom friction coefficient, U is the depth-averaged current velocity, and h is the total water depth.

The second option is a subgrid turbulence model given by

     νc=(c0u*h)2+(csm2ΔxΔy|S|)2

where c0 is an empirical coefficient approximately equal to 1/6, csm is an empirical coefficient between 0.25-0.5, Δx and Δy are the grid dimensions in the x and y directions, and |S| is equal to

     |S|=2(Ux)2+2(Vy)2+(Uy+Vx)2

The wave component of the eddy viscosity is calculated as

     νw=k(D/ρ)1/3

where k is an empirical coefficient, ρ is the water density, and D is the total wave dissipation.



CMS-Flow