[aspect-devel] ASPECT question

[Thomas Geenen]

hi Erik,

i experimented with that in the past and it helps a bit but do not expect
miracles.
there are other "tricks" to make it converge but those are kind of hacks.
otherwise you might want to experiment with your solver settings.
increasing the accuracy of the velocity subsystem solve and increasing the
value for the threshold (Amg_data.aggregation_threshold in assembly.cc)
 could improve the convergence in these cases.
of course increasing the resolution at the velocity jump would not harm you
either.

best
Thomas



On Thu, Apr 24, 2014 at 2:50 PM, Timo Heister <heister at clemson.edu> wrote:

> (sending to the mailing list)
>
> > I had a quick question about ASPECT.  I’m working on recreating the 2008
> Zhong spherical shell benchmarks which involve temperature dependent
> viscosity jumps up to the order of 1e7.  I notice in the simple material
> model there is an upper and lower bound on viscosity temperature dependence
> of 1e2 and 1e-2.  Is there a particular reason for this limit?
>
> This was introduced by Rene way back. I guess it makes sense to limit
> in in some way to make the model solvable.
>
> > If the limit is in the code then the solver fails to converge for large
> thermal viscosity exponents after a few hundred steps, but if I remove
> these bounds it appears to work fine.
>
> What is your viscosity range in that case? I haven't tested 'very
> large' viscosity contrasts yet. There might be stuff that needs
> changing in ASPECT to make it work. One thing you can try is using a
> constant viscosity per cell for example.
>
> --
> Timo Heister
> http://www.math.clemson.edu/~heister/
> _______________________________________________
> Aspect-devel mailing list
> Aspect-devel at geodynamics.org
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