# max courant/courant...velocity spikes?

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 September 1, 2010, 12:55 max courant/courant...velocity spikes? #1 New Member   Matt James Join Date: Jun 2010 Location: Marinette,WI, USA Posts: 25 Rep Power: 8 Hi all, I'm running a turbulent half-channel flow (dynSmag). I'm wondering why the max courant number is being reported in the neighborhood of 10-12 while the mean courant is around 0.3, where i calculated it based on expected mean flow. Where might these wild velocity fluctuations be coming from? Thanks very much for any help!

 September 17, 2010, 00:59 #2 Senior Member   Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,907 Rep Power: 27 Have you very refined cells somewhere in your domain? __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using.

 September 17, 2010, 13:08 #3 New Member   Matt James Join Date: Jun 2010 Location: Marinette,WI, USA Posts: 25 Rep Power: 8 Ah, yes. I have some near wall refinement but only in the wall normal direction. Eddy generation and therefore v and w velocities occurring I suppose?

 September 21, 2010, 15:06 #4 Senior Member   Steven van Haren Join Date: Aug 2010 Location: The Netherlands Posts: 149 Rep Power: 8 Have the same "problem" in my channel flow LES/DNS. If you are interested you can use the Co utility to determine where the high Courant number appears.

September 24, 2010, 03:32
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Hello,
i have two questions.

Quote:
 Originally Posted by mdjames Hi all, I'm running a turbulent half-channel flow (dynSmag). I'm wondering why the max courant number is being reported in the neighborhood of 10-12 while the mean courant is around 0.3, where i calculated it based on expected mean flow.
How can you find mean courant number? because in terminal min and max courant number is displaying only.

Quote:
 Originally Posted by stevenvanharen Have the same "problem" in my channel flow LES/DNS. If you are interested you can use the Co utility to determine where the high Courant number appears.
Is it possible to tell more about Co utility?

 September 24, 2010, 04:20 #6 Senior Member   Steven van Haren Join Date: Aug 2010 Location: The Netherlands Posts: 149 Rep Power: 8 Which solver are u using? I get mean and max Co in my terminal window using channelFoam/channelOodles. Co utility should be in your openfoam folder. Just use Co -help to see how it works.

September 24, 2010, 05:44
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Quote:
 Originally Posted by stevenvanharen Which solver are u using? I get mean and max Co in my terminal window using channelFoam/channelOodles. Co utility should be in your openfoam folder. Just use Co -help to see how it works.
i use pisoFoam. i want solve a rearward facing step with RAS and LES. my problem is i don't know how much can courant be large in solving process. do you know about it?

 September 24, 2010, 06:26 #8 Senior Member   Steven van Haren Join Date: Aug 2010 Location: The Netherlands Posts: 149 Rep Power: 8 RAS, no idea LES, max CFL ~ 0.5

September 24, 2010, 09:13
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Quote:
 Originally Posted by stevenvanharen RAS, no idea LES, max CFL ~ 0.5
is it a law for LES or it depends on cases? also please tell your reference.
Best regards.

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