[Getdp] simple 3d electrostatic problem

Gilles Grégoire schaouette at free.fr
Mon Jan 2 11:33:01 CET 2006

Le Lundi 2 Janvier 2006 10:20, Michal Hajek a écrit :
> Hello,
>
> I am working on a quite simple electrostatic example. Unfortunately, I
> must be doing some stupid mistake, since in calculation I still get
>
> "Warning   : Generated system is of dimension zero"
>
> and later on:
>
> "Warning   : No equations in linear system"

>
> My .geo, .pro and .msh definitions can be found at:
> http://material.karlov.mff.cuni.cz/people/hajek/getdp/
>
> I have spent last few days trying to localise my mistake. Finally, I
> decided to ask honestly the list.
This problem occurs generally because there is a problem in the geo
definition. The geo file opens fine wityh Gmsh, but GetDP as problem with it.

I tried your formulation with the simple geo file "cube.geo" and it works
fine. (I include it at the end of my reply)

You should therefore try to find the problem in your geometry file.
You could also rewrite your file a simpler way to avoid any mistake :  your
geometry is basically a H surface extruded in the y direction.
You can write something like:

/* Points necessarry to describe the H surface (12 at least), in the (x,z)
plan */
Point(1) = ...
...

/* Definition of the H surface*/
Line Loop(1) = {1,2,3,....,12};
Plane Surface(1) ={1};
/* Extrusion*/
Extrude Surface{1,{0,the_thickness_of_the_H,0}};;

/*eventually you define physical surfaces*/

SMALL TRICK:
After the extrusion you won't know the identification number for the surfaces
where you want to apply boundary conditions.
You can use Gmsh to help you:
Open the geometry file and then point the mouse on the surfaces you would like
to know: the identification number of the surface appears at the bottom of
the window, for example:
surface 18 {19,20,21,22}

Good luck!

--
Gilles Grégoire

>
> My intention is to put this problem into wiki after I have it successfully
> solved. :)
Great idea.
>
> Thanks a lot in advance.
>
> Best regards
> Michal
> _______________________________________________
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> getdp at geuz.org
> http://www.geuz.org/mailman/listinfo/getdp

/****************************************************
"cube.geo"
****************************************************/
lc = 1;

Point(1) = {0,0,0,lc};
Point(2) = {0,1,0,lc};
Point(3) = {0,1,1,lc};
Point(4) = {0,0,1,lc};
Line(1) = {1,2};
Line(2) = {2,3};
Line(3) = {3,4};
Line(4) = {4,1};
Line Loop(1) = {1,2,3,4};

Plane Surface(1) = {1};

v1[] = Extrude Surface {1,{10,0,0}};;

Physical Surface(1001) = {26};
Physical Surface(1003) = {1};
Physical Volume(10001) = {v1[1]};