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mesh resolution for DNS with high prandtl number

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Old   January 10, 2014, 11:14
Default mesh resolution for DNS with high prandtl number
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Hassan Nemati
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Dears
I am doing DNS with high prandtle number fluid (Pr=15).
1- Could someone tell me the best resolution for DNS.
2- For high Pr number I should go finer mesh, Could someone tell me what is the relation between Pr and factor of mesh resolution.
Bests
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Old   January 10, 2014, 11:39
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Filippo Maria Denaro
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Originally Posted by hnemati View Post
Dears
I am doing DNS with high prandtle number fluid (Pr=15).
1- Could someone tell me the best resolution for DNS.
2- For high Pr number I should go finer mesh, Could someone tell me what is the relation between Pr and factor of mesh resolution.
Bests

Just consider the Peclet number = Re*Pr in the energy equation as the same way as you consider only the Re number in the momentum
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Old   January 11, 2014, 00:40
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I think I remember from University that the resolution should be the kolmogorov length.

http://en.wikipedia.org/wiki/Kolmogorov_microscales

It is not alway ease to find the right epsilon. You can try to estimate it due to Reynolds number and boundary condition or run a coarse grid simulation with k-e turbulence.
How do you want to run a DNS anyway. I remember running some LES-code at University for several weeks on clusters (and DNS can be factors of magnitude more expensive).

Anyway, good luck and fun
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