[aspect-devel] Checkerboard at large scale

[Wolfgang Bangerth]

On 04/05/2018 10:20 PM, Lev Karatun wrote:
> One more thing that I forgot to mention in my original email: the model 
> works fine with free surface enabled, and only crashes with free slip at 
> the top.

As the others have already noticed, this points to the fact that you're 
putting more mass in than you're taking out via your boundary conditions 
(or the other way around), and that the equations don't allow this. You 
could observe this in two different ways:
* The pressure should then either get very large of very negative to 
account for the mass imbalance
* If you use a free surface, you should be able to see that it has a 
bulk motion up or down that accommodates the added/missing mass.

Either would be useful observations if you wanted to figure out whether 
the incompatibility of boundary conditions is the problem.

Best
  W.

-- 
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Wolfgang Bangerth          email:                 bangerth at colostate.edu
                            www: http://www.math.colostate.edu/~bangerth/