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-   -   Question on Courant no in userguide (http://www.cfd-online.com/Forums/openfoam-solving/59155-question-courant-no-userguide.html)

lakeat February 9, 2008 02:15

It is said on ferziger's book,
 
It is said on ferziger's book, that Courant number should be less than one if explicit scheme is used. (Correct me if i am wrong).

I see from icoFoam or turbFoam or oodles that the discretization schemes of temporal and convective and viscous terms are implicit, but pressure terms are explicit.

But in userguide, Co<1 is demanded for reason of "accuracy" and "stability".

So, my questions are:

1. do I still need to think for courant no. since many terms are discretized implicitly?

2. I want to be clear, whether my result is "correct" once my courant number was larger than one during calculation? What I believe is the word "correct" is more important than "accuracy" and "stability".

3. What's the relationship between "stable" and "correct"? I mean what if my courant no. is, say 2 or 3, of which it is said to be unstable, can i believe my result to be correct? Must I be concerned for stability all the way?

Thanks for your patience.

And finally, Happy new year to you all. (I 'm from China)

Daniel


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