Thank you very much (I am very late, but I hope not too late).
After a forced pause I made a new attempt and found that a naive cut
produced a quite distorted mesh that caused numeric problems, I
assume. I am happier with plugin(CutGrid) now.
After fixing the parameters, plugin(Intergrate) started to provide
values with actually sufficient accuracy, but I will switch to global
quantities later, as you suggested.
Kind regards, Thomas
Zitat von Christophe Geuzaine <cgeuza...@uliege.be>:
On 5 Aug 2020, at 10:12, t.esch...@dokom.net wrote:
Dear all,
trying to get acquainted with gmsh/getdp, I stumbled upon two
problems that I am not able to resolve.
I am trying to model a simple conductive cell with two electrodes,
a simple one and a structured one. To me, the results look quite
realistic so far (I am still in the stage of checking), with two
exceptions:
The first: When I try to calculate the overall current by calling
plugin(Integrate) on views slightly above the simple electrode, I
get two different results (for the vector view -8,88 and the
x-component view -39,9), and neither is close enough to the
expected value of -2x(4,94..4,99).
Be careful with brute-force integration. If you use GetDP would
recommend using global quantities, which define such integrals in
the "variationally correct" way: see e.g.
https://gitlab.onelab.info/doc/tutorials/-/wikis/Electrostatics-with-floating-potentials
The second: The current density field has few spiky values that I
do not know how to cure. Their position seems to be constant, the
values seem to change with the grid parameters, and it might be
getdp-related.
With a (scalar) potential formulation your current density is
defined through the gradient, whose accuracy will depend quite
strongly on the mesh quality. You can give the new "HXT" 3D
algorithm a try, whose optimizer produces slightly better elements,
and see if this improves things.
Christophe
Please, have a look and give me a hint on how to correct/proceed. Thank you.
Kind regards, Thomas
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Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer
Sciencehttp://www.montefiore.ulg.ac.be/~geuzaine
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