> The mesh has over 100000 cells in it, it is super refined. And oddly, when
> the refinement level is less, it doesn't blow up. It's only after a
> certain point.
> it is an even global refinement, starting from a hyper divided rectangle.
> no fancy refinement.
>
> I only realised this as I wasn't getting the right convergence rates for v
> at the lower refinement levels so I just kept going up to see if it
> eventually did and it blew up.
> Until this point, at the refinement levels that work, the pressure
> converges correctly at two consecutive degrees, and so does v at the
> higher degree. but at the lower degree, the convergence rates for v were
> decreasing with refinement.
> That;s why I continued to refine then came across this situation.
>
> Seeing that it is only at the bottom, and noticing that if I used
> Dirichlet condition on that boundary, then the solution doesn't blow up
> and converges correctly, I can only assume it's to do with the normal flux
> condition there, which i think I'm imposing correctly.
Jane -- I don't think anyone other than you is in a position to figure this
out. I've learned to debug problems with a mind set of assuming that
everything I believe is correct may in fact not. So when you say
"I can only assume it's to do with the normal flux condition there, which
i think I'm imposing correctly"
then my approach is to assume that they are not imposed correctly, and to
write code that helps me to *verify* that it is.
As an example, even though you think that you've set the boundary indicators
correctly at all cells on the bottom, this may not be the case for whatever
reason. Write a loop over all cells and all boundary faces and *output*
location and boundary indicator, to make sure it is. Go through this sort of
procedure for everything you *believe* should be true to make sure that it
*is* true.
I'm sorry I have no other suggestions for what to do. We've all been in your
situation where stuff doesn't work for reasons that seem completely
mysterious. The successful among us are the ones who have built the mental and
computer skills to figure out what the cause is. Among the mental skills is
the ability to assume that what one believes to be true (because one has
written the code) may not be so. The computer skills is then to use a debugger
or print statements in the right places to verify that something is indeed the
case or not, and to narrow down the possible root causes.
Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google Groups
"deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
