[aspect-devel] Aspect-devel Digest, Vol 12, Issue 3

John Naliboff jbnaliboff at ucdavis.edu
Thu Nov 15 19:48:38 PST 2012

Hi all,

I sent an email off earlier today with a plot of basal verse surface heat flow, but it looks like it still needs to be approved due to the attached image size.  If it went through and this image is a repeat, apologies.

I've attached a plot showing the basal and surface heat flow for a spherical shell model I'm currently running.  The Ra number is ~ 7.66e5.  The model has not completely reached steady state yet, but if the trend continues there will be a distinct gap between the surface and basal heat flow.  The .prm file I used to run the model is also attached.

The gap is only around a factor of 2, but again it appears to be growing as the model moves toward steady state.

In terms of resolution, I did 4 initial global refinement steps, 3 initial adaptive refinement steps, and the coarsening and refinement fractions are, respectively, 0.05 and 0.3.

I'll try increasing the refinement fraction and initial refinements to see if this reduces the gap between the global and surface heat fluxes. I am bit surprised that the mesh parameters above did not adequately resolve the basal boundary layer, if this is also the issue in my models.


On Nov 15, 2012, at 9:25 PM, Wolfgang Bangerth wrote:

> On 11/15/2012 03:59 PM, Ian Rose wrote:
>> Problem (probably) solved.
>> The lower boundary, having a smaller surface area, requires a thinner
>> boundary layer to keep up with the heat flux out of the top boundary.
>> If you run at too low a resolution (as I was), then the temperature
>> gradient at the bottom is too shallow due to numerical diffusion and you
>> significantly underestimate the lower  heat flux.
> Wow, by a factor of 4? Then, anyway, glad you found what looks like the 
> reason.
> Best
>  W.
> -- 
> ------------------------------------------------------------------------
> Wolfgang Bangerth               email:            bangerth at math.tamu.edu
>                                 www: http://www.math.tamu.edu/~bangerth/
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