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-   -   time steps in LES (http://www.cfd-online.com/Forums/fluent/30392-time-steps-les.html)

Jimmy October 14, 2002 09:41

time steps in LES
 
could someone give me a good method to set a correct time step in LES simulations. The only infos given by the manual says : "under 20 iteration to converge"

i'm not sure this is a good argument to put in a scientific work :)

I've tried using a CFL condition witch could be interpreted as : "the information cannot jump to the next cell during one time step" but the CFL conditions given in the manual refers to the coupled solver and i use the segregated one.

any idea ?

fb October 14, 2002 10:07

Re: time steps in LES
 
You can just consider the max. streamwise velocity and the smallest cell size in the same direction to evaluate a time step (this will be cfl~1).

For exemple channel flow with streamwise x direction with vmoy ~1 and DeltaX =0.01 => Delta t= 0.01 ....

Jimmy October 14, 2002 10:44

Re: time steps in LES
 
that's what i'm actually using, while adapted after some readings to CFL=0.3

but this is true only for stability in explicit time integration, is there a good justification for this in an implicit second order time integration ?


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