[aspect-devel] ASPECT question

[Rene Gassmoeller]

Hi all,

>>> 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.
>>

The limit indeed is only there, to prevent 'huge' viscosity jumps
accidentally inputted by the user. The actual values are somewhat
arbitrary (comparable to what I used before in CitcomS). Maybe we should
loosen the bounds anyway, so that anyone, who wants to recreate such
benchmarks does not need to change the code.

>>> 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.

Strange, if it really seems to hurt the codes stability, then feel free
to change or remove them. They were intended to increase stability, when
we first implemented this temperature dependency, but I did not look
into the behaviour of this material model for a while.

Cheers,
Rene