[aspect-devel] Internal heating in aspect (Ludovic Jeanniot)

[Max Rudolph]

On Tue, Sep 4, 2018 at 5:03 PM Wolfgang Bangerth <bangerth at colostate.edu>
wrote:

> On 09/04/2018 05:41 PM, Rene Gassmoeller wrote:
> > following our discussion last week I sat together with Max Rudolph here
> at UC
> > Davis and discussed a few possibilities for modifying the current
> > stabilization scheme in ASPECT to overcome the difficulties that were
> > discussed, i.e. (apparent) imbalance of steady-state heat flux across
> the
> > boundaries due to strong artificial diffusion through the boundary
> layers and
> > thus a modified average temperature (all for models with a low to medium
> > resolution of 3-5 global refinements in the boundary layer).
>
> First, thanks for tracking these things down!
>
> I have a completely tangential question: Right now, when we compute the
> heat
> flux across a boundary, we only consider the physical component of it, but
> not
> the part of that results from the artificial diffusion. Even if we had a
> discretization that is energy conservative, this would mean that the net
> heat
> flux through the boundaries (as currently computed) is not balanced.
> Should we
> modify the postprocessor to also take into account the artificial
> diffusion
> factor?
>
>
Rene and I discussed this idea on Monday and I don't think that this is the
right thing to do. It would lead to an unexpected relationship between the
temperature gradient (and hence temperature structure of the lithosphere)
and the physical thermal conductivity. Maybe more helpful would be a
separate output of the non-physical contribution to the heat flux through
each boundary, or within the entire domain as the ratio of the norm of the
artificial heat flux divided by the norm of the total heat flux. I still
think that a warning message when this quantity exceeds, say, 1% would help
users understand that they should expect unphysical results.

Best
>   W.
>
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth          email:                 bangerth at colostate.edu
>                             www: http://www.math.colostate.edu/~bangerth/
>
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