CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM (http://www.cfd-online.com/Forums/openfoam/)
-   -   max courant/courant...velocity spikes? (http://www.cfd-online.com/Forums/openfoam/79724-max-courant-courant-velocity-spikes.html)

mdjames September 1, 2010 12:55

max courant/courant...velocity spikes?
 
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!

alberto September 17, 2010 00:59

Have you very refined cells somewhere in your domain?

mdjames September 17, 2010 13:08

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?

stevenvanharen September 21, 2010 15:06

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.

maysmech September 24, 2010 03:32

Hello,
i have two questions.

Quote:

Originally Posted by mdjames (Post 273635)
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 (Post 276040)
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?

stevenvanharen September 24, 2010 04:20

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.

maysmech September 24, 2010 05:44

Quote:

Originally Posted by stevenvanharen (Post 276456)
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?

stevenvanharen September 24, 2010 06:26

RAS, no idea
LES, max CFL ~ 0.5

maysmech September 24, 2010 09:13

Quote:

Originally Posted by stevenvanharen (Post 276484)
RAS, no idea
LES, max CFL ~ 0.5

Thanks for your reply.
is it a law for LES or it depends on cases? also please tell your reference.
Best regards.


All times are GMT -4. The time now is 01:03.