[Gmsh] double surfaces/lines between adjacent bodies
Zenker, Dr. Matthias
Matthias.Zenker at erbe-med.de
Thu Mar 12 09:10:47 CET 2009
Hi Mark,
this would be exactly what I need...
Best regards,
Matthias
> -----Original Message-----
> From: Mark van Doesburg [mailto:mark.van.doesburg at technolution.nl]
> Sent: Wednesday, March 11, 2009 5:51 PM
> To: Zenker, Dr. Matthias; gmsh at geuz.org; elmerdiscussion at postit.csc.fi
> Subject: Re: [Gmsh] double surfaces/lines between adjacent bodies
>
> Hello Matthias,
>
> I have the same problem and am working on a solution. This
> solution consists of an algorithm which uses OpenCASCADE to
> find all overlapping vertices/edges and surfaces and merge
> them. This includes partial overlaps.
>
> With a partial overlap I mean for example a small edge with
> overlaps a larger edge in the middle. The algorithm will
> split the longer edge in three pieces and the overlapping
> section is merged. As similar method is used to merge
> partially overlapping surfaces.
>
> I was creating this as part of a BRL-CAD reader for gmsh, but
> it is probably usefull for all OpenCASCADE models.
> Unfortunately it is not yet finished.
>
> regards,
>
> Mark van Doesburg
>
> "Zenker, Dr. Matthias" <Matthias.Zenker at erbe-med.de> wrote:
>
> Hi Elmer and gmsh list,
>
> I use gmsh and Elmer to simulate an electrical current
> flowing through a
> conductive medium between two electrodes. I get the
> geometry from my CAD
> colleagues in STEP format, import it in gmsh, mesh it,
> read the mesh
> with Elmer and do the FEM calculation there. Most of
> the time, the
> calculations are 2D. This works in principle, but there
> is the following
> problem:
> Electrode and medium have common surfaces (resp. lines
> in 2D). When I
> get the geometry in STEP format, every part (Electrodes
> and Medium) has
> its own outer surface (line). This leads to double
> surfaces (lines)
> between the adjacent bodies. For geometry and mesh
> import, this is no
> problem, neither for gmsh nor for elmer - the mesh is
> imported OK in
> Elmer. But when I do the simulation, I see that no
> current flows through
> this double surface (although only one of them is
> defined as physical in
> gmsh, and only that one is seen in Elmer).
> Removing the double surface/line in gmsh is rather
> tedious (Identify the
> problematic regions where there is a double line
> between adjacent
> surfaces. Delete at least one of the adjacent surfaces.
> Delete the
> corresponding line at the interface. Delete its points.
> Redefine the
> surface(s) which was (were) deleted before. It gets
> more complicated in
> case of only partially overlapping lines which have to
> be partially
> reconstructed.).
>
> Question: How do I deal with this problem? Is there a
> more elegant (and
> less time consuming) way than manual removal of the
> double lines? (The
> autocoherence function in gmsh which is intended to
> remove double
> duplicate entities in geometries is switched on, but
> does not seem to
> have any effect.)
> I imagine that this must be a known problem, since
> doing simulations
> with geometries imported from 3D CAD systems is not so
> uncommon after
> all.
> Further it is not totally clear to me where the problem
> really comes
> from. I suspect non-identical mesh nodes at the
> interface, which inhibit
> current flow across the border.
>
> Ideas and suggestions are more than welcome...
>
> Thank you,
>
> Matthias
>
> ----------------------------------------------------------------
> ERBE Elektromedizin GmbH
> Dr.rer.nat. Matthias Zenker
> Dipl. Phys.
> Grundlagenentwicklung Technologie
> Waldhoernlestrasse 17
> 72072 Tuebingen
> Phone + 49 7071 - 755 226
> Fax + 49 7071 - 755 5226
> mailto:Matthias.Zenker at ERBE-med.de
> www.ERBE-med.de
> ----------------------------------------------------------------
>
>
>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>
>
_____________________________________________________________________
ERBE Elektromedizin GmbH
Firmensitz: 72072 Tuebingen
Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
Registergericht: Stuttgart HRB 380137