[aspect-devel] compressibility in 2d

[Wolfgang Bangerth]

> Thanks for the quick reply and answers. We have been discussing this (with Wim
> and Cedric), and at first we still found it strange that the 2D case of the
> Stokes equation yields a different deviator in the matrix (1/2 vs 1/3). But
> then we realised that in the truly 2D case all the units should also be
> different anyway (e.g. density kg/m2, pressure N/m, etc) and one should
> actually derive the whole thing from the beginning in 2D. In Aspect and other
> codes we always work in 2D with true physical units, e.g. density in kg/m^3,
> pressure N/m2 etc, implicitly assuming a finite width of the 2D slice, i.e. we
> implicitly  work with 3D physics and therefore the “⅓” is okay.
>
> I guess something like this should be added somewhere in the manual, but for
> now I think my question is answered.

Yes. I meant to put something in the manual, but I can't seem to find time for 
these things right now, so I opened
   https://github.com/geodynamics/aspect/issues/1390

Best
  W.

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