I’ve been experiencing issues in the temperature field while using 3D spherical geometries (both the 3D chunk and 3D spherical shell). I’m using a temperature dependent viscosity from the simple material model in a fairly simple mantle convection set up. The two issues are that even though I have the outer and inner boundaries set to prescribed temps (273 and 2000K respectively) the min and max temperatures will exceed those bounds reaching negative temps and some several hundred degrees higher, and I am seeing oscillations in both the temperature and viscosity in visualizations.
The oscillations were somewhat near the boundaries so Rene suggested trying discontinuous temperature discretization, and testing on the 90 degree opening of the 3D spherical shell. The discontinuous temperature discretization case had the same issues and the temperature would exceed the prescribed global temperature minimum and maximums, especially along the boundaries
I tested the 90 degree opening with both an isoviscous (simpler material model) and temperature dependent viscosity (simple material model) case and it also had issues with the temperatures running out of control in both cases.
This is the header with the Aspect and deal.ii version as well.