CMS-Flow:Subgrid Turbulence Model: Difference between revisions

From CIRPwiki
Jump to navigation Jump to search
Line 20: Line 20:
The mixing length is calculated here as   
The mixing length is calculated here as   


       <math>l_h = \kappa \textrm{min}( \sqrt{\Delta x \Delta y}, c_{sm} h )  </math>  
       <math>l_h = c_{sm} \textrm{min}( \sqrt{\Delta x \Delta y}, h )  </math>  


where <math>c_{sm}</math>  is an empirical coefficient (Smagorinsky coefficient).
where <math>c_{sm}</math>  is an empirical coefficient (Smagorinsky coefficient).

Revision as of 21:52, 25 November 2009

Subgrid Turbulence Model

In CMS-Flow eddy viscosity is calculated as

       

where is weighting factor equal to in which is the significant wave height and and are the current- and wave-related eddy viscosity components respectively. The wave contribution is included using the equation of Kraus and Larson (1991)

     

where is an empirical coefficient (default is 0.5), and is the wave bottom orbital velocity and is the water depth. The current-related eddy viscosity is calculated as a function of the flow gradients, and the bottom shear stress

     

where is a base value approximately equal to the kinematic viscosity, is an empirical coefficient, is the subgrid mixing length, and is equal to

     

The mixing length is calculated here as

      

where 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