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

[Juliane Dannberg]

Hi all,

On 08/29/2018 01:54 PM, Scott King wrote:
> Looking at Max’s results, could there be a 1/r^n or r^n term missing in the artificial diffusivity calculation?
I think the reason for the lower artificial diffusion closer to the 
core-mantle boundary is just the different cell size. The stabilization 
scales with the actual cell size, so it is smaller for smaller cells.
But I agree that this becomes a substantial problem as soon as the 
artificial diffusion approaches (or even exceeds) the physical 
diffusion, as in Max' example. This also made me wonder if this is one 
of the reasons why the problem is more apparent in spherical models. In 
a box model, the diffusion that's added is similar at the top and bottom 
(at least for a uniform grid), while in the spherical case, it's much 
bigger the closer you get to the surface, which leads to a big asymmetry 
of the heat flux, and a change in temperature.

Best,
Juliane

>
>> On Aug 28, 2018, at 11:01 PM, Wolfgang Bangerth <bangerth at colostate.edu> wrote:
>>
>> On 08/28/2018 05:33 PM, Max Rudolph wrote:
>>>  From this, it is very obvious why the solution to the convection problem at low resolution is very diffusive and also why the interior temperature is much closer to the surface temperature than to the CMB temperature because the artificial viscosity is on the order of 20 times larger than the thermal conductivity near the surface.
>> Would it be easy to verify whether the artificial viscosity ("artificial conductivity") decreases at the expected rate with mesh refinement?
>>
>>
>>> For the conduction problem, the default values of the artificial viscosity are also much larger than the thermal conductivity.
>> I think that's the point worth investigating. Since in this case the velocity is zero, one would expect the artificial viscosity to also be at least quite small. Why is it not?
>>
>> Best
>> W.
>>
>> -- 
>> ------------------------------------------------------------------------
>> Wolfgang Bangerth          email:                 bangerth at colostate.edu
>>                            www: http://www.math.colostate.edu/~bangerth/
>>
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----------------------------------------------------------------------
Juliane Dannberg
Project Scientist, UC Davis
jdannberg.github.io <https://jdannberg.github.io/>


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