[aspect-devel] Difficulties with tracers and material model

[Timo Heister]

Dear Adriaan,

sorry for net getting back to your email earlier.

>>> - In many of my models I model plasticity by using a Material Model
>>> implementing the new Interface. Often, though not always, there are
>>> unexpected
>>> irregularities (viscosity jumps) in the corners. I found  that the
>>> evaluate()
>>> method of the Material Model is never called with a position Point in the
>>> corners before the Stokes equation is solved. However, afterwards the
>>> evaluate() method is called by the Viscosity postprocessor.
>>
>>
>> You mean the point is never in a corner when assembling the linear
>> systems, but it may be in a corner when using a postprocessor? That is
>> correct --  we assemble linear systems using Gauss quadrature formulas where
>> all quadrature points are in the interior of a cell. But we do output data
>> using evaluation points that are the vertices of cells.
>>
>> Can you explain how this leads to problems in your models?
>
> If I understand this correctly the problem is limited to the visualization?
> (here is an example VTU screenshot:
> http://img196.imageshack.us/img196/5954/corners.png)

Can you explain what the material model is and what you expect to see
here? This image highlights some bug for sure (be it in your material
model, the solver, or in the output).

> What I intend to do is flipping on and off the "Nonlinear iteration"
> parameter in the input file. However, even when "Nonlinear iteration" is
> false, and "Nonlinear solver scheme" is set (f.e. to "iterated IMPES")
> nonlinear iterations are executed. This is the case for box.prm and the
> parameter file I send you.

"Nonlinear iteration" was a left over parameter that did not have any
effect. Therefore, I removed this parameter. You should use "Nonlinear
solver scheme".

Best,
Timo

--
Timo Heister
http://www.math.tamu.edu/~heister/