[CIG-SHORT] Gravity on Large/Heterogeneous Meshes

[Brad Aagaard]

Scott,

There are a couple of issues to consider:
(1) If you have nonuniform density, then the initial stresses as a 
function of depth are more complicated than a constant linear increase 
with depth. You need to calculate the lithostatic stress as a function 
of depth and use that for the initial stresses.
(2) Tighten the convergence tolerance (ksp_rtol and ksp_atol) to get a 
more accurate solution.

Regards,
Brad


On 11/11/12 4:25 PM, Scott Henderson wrote:
> Hello,
>
> I've been modifying the step16.cfg tutorial for a larger mesh. If I
> increase the domain size from 6x6x4 to 200x200x100km, and change the
> initial_stress.spatialdb to correspond to the new lithostatic stress
> at the base of the mesh (-2451637500Pa). I'm finding that the elastic
> solution has ~2 cm of subsidence at the surface, but I expect zero
> displacement. This appears to be independent of element size.
>
> Also, if I have non-uniform density in the mesh (for example an
> embedded weak layer or arbitrary shape), how might I set up the
> initial stresses to compensate for gravity? I'm guessing that the
> only way to go about this is run the solution without initial
> stresses, extract the stress values at a few points through each
> material, then set up separate spatial databases for each material
> for the next run?
>
> Thanks, Scott
>
> step16_1 = same settings as step16, but larger mesh step16_2 = just
> elastic solution
>
>
>
>
>
>
>
> _______________________________________________ CIG-SHORT mailing
> list CIG-SHORT at geodynamics.org
> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>