CMS-Flow:Subgrid Turbulence Model: Difference between revisions

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== Subgrid Turbulence Model ==
== Subgrid Turbulence Model ==


In CMS-Flow eddy viscosity is calculated as <math> \nu_t = (1-\theta_m)\nu_{tc} + \theta_m \nu_m </math>  where <math>\theta_m</math>  is weighting factor equal to <math>\theta_m = (H_s/h)^3 </math>  in which <math>H_s</math>  is the significant wave height and <math>\nu_{tc}</math>  and <math>\nu_{tw}</math>  are the current- and wave-related eddy viscosity components respectively. The wave contribution is included using the equation of Kraus and Larson (1991)  <math> \nu_tw = \Lambda u_w h </math>, where  <math>\Lambda</math> is an empirical coefficient (default is 0.5), and  <math>u_w</math> is the wave bottom orbital velocity. The current-related eddy viscosity is calculated as a function of the flow gradients, and the bottom shear stress
In CMS-Flow eddy viscosity is calculated as  


       <math> \nu_{tc} = \nu_{t0} + \sqrt{ (c_0 u_* h)^2 + (c_{sm}^2 \Delta x \Delta y |S| )^2 } + k(D/\rho)^{1/3}</math>
       <math> \nu_{tc} = \nu_{t0} + \sqrt{ (c_0 u_* h)^2 + (c_{sm}^2 \Delta x \Delta y |S| )^2 } + k(D/\rho)^{1/3}</math>

Revision as of 21:39, 2 November 2009

Subgrid Turbulence Model

In CMS-Flow eddy viscosity is calculated as

where is a base value approximately equal to the dynamic viscosity, and is an empirical coefficient and is an empirical coefficient (Smagorinsky coefficient).

References

LARSON, M.; HANSON, H., and KRAUS, N. C., 2003. Numerical modeling of beach topography change. Advances in Coastal Modeling, V.C. Lakhan (eds.), Elsevier Oceanography Series, 67, Amsterdam, The Netherlands, 337-365.

CMS-Flow

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