mesh resolution for DNS with high prandtl number

hnemati · January 10, 2014, 11:14

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

FMDenaro · January 10, 2014, 11:39

Quote:

Originally Posted by hnemati

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

beer · January 11, 2014, 00:40

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

January 10, 2014, 11:14	mesh resolution for DNS with high prandtl number	#1
hnemati Member SAM Join Date: Apr 2012 Posts: 74 Rep Power: 14	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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January 11, 2014, 00:40		#3
beer Member Join Date: Dec 2012 Posts: 92 Rep Power: 14	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