[Gmsh] R: Integer flag to .msh elements

Thu Oct 24 15:36:15 CEST 2013

On 24/10/13 13:38, Alessandro Vicini wrote:

> Hullo everybody,
>
> the problem is (as far as I know), that when you assign a surface to a
> physical group, you don't have control on the number of the group, which is
> automatically assigned by Gmesh.

No. See t1.geo. If you write

Physical Surface (5555) = {6} ;

in t1.geo file, mesh it and save the mesh, the elements belonging to surface 6 will be tagged with 
the 5555 integer.

ace35:~/gmsh/tutorial >   cat  t1.msh

$MeshFormat
2.2 0 8
$EndMeshFormat
$Nodes
427
1 0 0 0
2 0.1 0 0
3 0.1 0.3 0
4 0 0.3 0
5 0.009999999999982483 0 0
6 0.019999999999956 0 0
7 0.02999999999992728 0 0
8 0.03999999999989585 0 0
...
...
...
426 0.01732880869837657 0.1002635856800227 0
427 0.06912838083014602 0.1057967588383864 0
$EndNodes
$Elements
844
1 15 2 1 1 1
2 15 2 1 2 2
3 1 2 99 1 1 5
4 1 2 99 1 5 6
5 1 2 99 1 6 7
...
...
...
71 1 2 99 4 79 80
72 1 2 99 4 80 1
73 2 2 5555 6 33 308 214
       #####

74 2 2 5555 6 105 229 284
75 2 2 5555 6 106 228 285
76 2 2 5555 6 122 234 316
77 2 2 5555 6 135 238 262
78 2 2 5555 6 60 166 282
79 2 2 5555 6 84 196 170
80 2 2 5555 6 97 197 170
81 2 2 5555 6 127 245 183
82 2 2 5555 6 54 164 270
83 2 2 5555 6 174 347 154
84 2 2 5555 6 84 170 337
85 2 2 5555 6 75 76 172
...
...
...

Dave

If I understand what Umberto is saying
> (which is the same thing that would be useful in my case), it would be nice
> to have the possibility of explicitly assigning these integer flags to
> surfaces (or groups of surfaces), in order to specify boundary conditions.
>
> Regards,
>
> Alessandro
>
>
>
> -----Messaggio originale-----
> Da: gmsh-bounces at ace20.montefiore.ulg.ac.be
> [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] Per conto di David Colignon
> Inviato: giovedì 24 ottobre 2013 13.02
> A: Umberto Iemma; gmsh at geuz.org
> Oggetto: Re: [Gmsh] Integer flag to .msh elements
>
>
> On 24/10/13 11:57, Umberto Iemma wrote:
>>
>> First, I'd like to thank the authors for the wonderful work they are doing
> !
>> Gmsh is one of the most useful free technical tools ever!
>> Thanks!
>>
>> After this, I have a question.
>>
>> It is possible to include in the .msh file a integer flag to each element
> ?
>> I need this to specify particular physical properties of the boundary.
>
>
> Hi Umberto,
>
> you should use Physical groups for that purpose, see
> http://geuz.org/gmsh/doc/texinfo/gmsh.html#Elementary-vs-physical-entities
>
> "Groups of elementary geometrical entities can also be defined and are
> called “physical” entities.
> These physical entities cannot be modified by geometry commands: their only
> purpose is to assemble elementary entities into larger groups, possibly
> modifying their orientation, so that they can be referred to by the mesh
> module as single entities. As is the case with elementary entities, each
> physical point, physical line, physical surface or physical volume must be
> assigned a unique identification number. "
>
>
> and tutorial t1.geo, http://geuz.org/gmsh/doc/texinfo/gmsh.html#t1_002egeo
>
>
> Regards,
>
> Dave
>
> --
> David Colignon, Ph.D.
> Collaborateur Logistique du F.R.S.-FNRS
> CÉCI - Consortium des Équipements de Calcul Intensif ACE - Applied &
> Computational Electromagnetics Université de Liège Sart-Tilman B28 10,
> Grande Traverse
> 4000 Liège - BELGIQUE
> Tél: +32 (0)4 366 37 32
> WWW:    http://www.ceci-hpc.be/
>
>>
>> I'm the coordinator of the open-source project AcouSTO
>> http://acousto.sourceforge.net, a tool for acoustic simulation. I'm
>> going to release soon version 1.6 including the possibility to read Gmsh
> files.
>> Everything is working fine and the release candidate could be issued
>> now, but this additional possibility would broaden significantly the
>> field of application.
>>
>> Thanks in advance,
>> Umberto
>>
>> *****************************************************************
>>      Prof. Umberto IEMMA
>>      Associate Professor of Aerospace Structures and Design
>>      Dip. di Ingegneria - Universita' Roma Tre
>>      via Vito Volterra 62, 00146 Roma
>>      tel. +39-0657333274 fax  +39-065593732
>>      www   : http://acousto.sourceforge.net
>> *****************************************************************
>>
>>
>>
>>
>>
>>
>>
>>
>>
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>
>
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