oh, sorry that you run into this. Let me also copy my reply to the
ASPECT forum, as it might be of interest to other users. You can reply
to this mail or via the forum at https://community.geodynamics.org/c/aspect.
Before looking into the convergence issues, make sure your viscosity
profile is set up correctly. You can do this by switching off the Stokes
solver and prescribe a velocity solution. This way you can check the
output files for viscosity. You can do this by adding the following to
the input file:
set Nonlinear solver scheme = single Advection, no Stokes
subsection Prescribed Stokes solution
set Model name = function
You also need to comment out all velocity boundary conditions (they are
not needed if you prescribe velocity everywhere).
If the viscosity looks correct, try the following: In general we have
seen that convergence got much better with higher resolutions, but for
that we of course need a good refinement strategy (to only resolve areas
viscosity is always a good refinement strategy for this
type of problems). Another solution we found during this year’s
hackathon was to set the following solver properties:
subsection Solver parameters
subsection Stokes solver parameters
set GMRES solver restart length = 200 # The default is 50
This seemed to help with the kind of convergence problem you are
encountering, but will need a bit more memory. If it works, it will
likely also resolve your point 2. Give it a try and let me know how it
goes, we were thinking of writing a recommendation for this setting.
Unfortunately we can not make it the default setting, as the increased
memory consumption limits ASPECT’s usability for other problems.