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-   -   Eddy Dissipation Rate for LES (http://www.cfd-online.com/Forums/cfx/77986-eddy-dissipation-rate-les.html)

rsin July 8, 2010 19:19

Eddy Dissipation Rate for LES
 
Hi,

I want to extract eddy dissipation rate for LES model. I do not understand how to do it. I have the required formula in front of me which says:

total edddy dissipation rate for LES = e = (Mut+Mu)/2*(du'/dy+dv'/dx)^2

I don't understand how to post process that?

I am using v12.1 of CFX. Any help will be appreciable.
Thanks

rsin July 15, 2010 03:17

Common guys! no-one has any idea? A little hint will be useful!

ghorrocks July 15, 2010 06:46

Do you want to evaluate it over the whole domain (ie create a field variable) or just at certain points or get a global value?

rsin July 15, 2010 21:07

i want to evaluate it both locally and globally.

ghorrocks July 16, 2010 08:33

Evaluating u' will be tricky. If you want fixed points you can get it by taking a moving time average of a monitor point but I can't see an easy way of doing it spatially. You will probably need user fortran to do this, and even then it will be tricky.

You may be able to determine a sort of bulk flow velocity by mapping the velocity field to an additional variable with some dissipation on it. If you adjust the dissipation to give an appropriate level of smoothing this can give you an smoothed velocity field which you can then evaluate u' from. This might work.

So it is easy to evaluate it a monitor points as a post processing operation.

rsin November 4, 2010 19:28

understood the method of obtaining the epsilon for LES
 
Please refer to the article
http://leskandepsilon.blogspot.com/2...y-for-les.html
This article is based on the understanding of how to obtain epsilon for LES.

Cheers


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