[Getdp] Simple electrostatic simulation yields nan values everywhere

Christophe Geuzaine cgeuzaine at uliege.be
Tue Sep 17 21:44:16 CEST 2019

Hi Théo,

You are integrating your volume stiffness matrix on DomainCC_Ele

  Galerkin { [ eps[] * Dof{d v} , {d v} ] ; In DomainCC_Ele ; Jacobian Vol ; Integration GradGrad ; }

but you define DomainCC_Ele to also include the (inner) boundary Skin_ins_conds

    DomainCC_Ele += Region[{Skin_ins_conds}] ;

Remove this and you should be fine.


> On 17 Sep 2019, at 17:34, Théo Mathurin <theo.mathurin at univ-artois.fr> wrote:
> Hello everyone,
> I've encountered a strange issue with my electrostatic computation. I'm using the V formulation with the electric potential v saved as a post-operation output (see pro file attached).
> The geometry is desperately simple: two conductors in a square surrounding medium, each with its insulation. When the conductors are round, everything's fine and the electric potential is computed correctly. But when their shape is changed to rectangular, for some reason I get nan values everywhere in the domain.
> My msh file is generated using the Gmsh Python API. Attached is the corresponding Python script, where one can switch the shape from circles to rectangles. For debugging purposes, the script is written so that the minimal amount of code that is not shared by the two cases is isolated behind a conditional statement.
> Apparently, the problem arises when and only when one or several of the left or right insulation outer curves are straight lines. I have checked that there is nothing wrong with physical regions.
> In both cases I'm using the same pro file, and the command to run GetDP is the following:
> getdp -pro electrostatics.pro -msh test_geom.msh -solve EleSta_vf -pos get_v
> Note that I was able to carry out the very same computation successfully in a different, much more complicated geometry with rectangular conductors. I sincerely have no idea as to the root of this seemingly intractable problem, and therefore any help would be greatly appreciated. If needed, I can also provide the msh files I get when I'm running my Python script.
> Other potentially relevant information below
> - Python API from Gmsh 4.4.1 Linux 64 bits SDK 
> - GetDP 3.2.0 Linux 64 bits
> - Python 3.7
> - Ubuntu 18.04.3
> Best regards,
> Théo Mathurin
> Research engineer
> Laboratoire Systèmes Electrotechniques et Environnement (LSEE) - Université d'Artois
> <test_geom.py><electrostatics.pro>_______________________________________________
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Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 

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