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-   -   Question about eddy viscosity ratio limit (http://www.cfd-online.com/Forums/cfx/25062-question-about-eddy-viscosity-ratio-limit.html)

Piti January 17, 2008 14:43

Question about eddy viscosity ratio limit
 
I'm doing particle tracking in a fluid flow system. The particles are 1 micron in diameter. I came across the term turbulent dispersion force, which seems to be quite important for small particles. This force is governed by eddy viscosity ratio limit and its default value is 5. Can anyone tell me the physical meaning of eddy viscosity and why the default value is 5? Are there any criteria in choosing the eddy viscosity ratio limit for a particular situation?

Glenn Horrocks January 17, 2008 17:38

Re: Question about eddy viscosity ratio limit
 
Hi,

I don't think it is discussed in the documentation, but I think this factor limits the magnitude of the random "nudges" given to the particle by the turbulent field. You will need to do some study in this parameter to find out if it is important of not to your simulation. Try increasing and decreasing it by a factor of 10 (say) and see if it makes a difference.

Glenn Horrocks

Piti January 17, 2008 17:49

Re: Question about eddy viscosity ratio limit
 
Thank you for you reply. I'll try that.


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