Re: [Gmsh] R: Integer flag to .msh elements

Thu, 24 Oct 2013 07:55:35 -0700 


On 24/10/13 16:52, Umberto Iemma wrote:

David,

Thanks for the help.

Does it work also for physical entities made of more than one surface?
i.e. Something like


Physical Surface (5555) = {6, 7, 22} ;



Yes, indeed.

Dave





I'm not at my pc and I can't check by myself now.

Thanks,
Umberto

Sent from my iPad


On 24/ott/2013, at 15:36, "David Colignon" <[email protected]> wrote:



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: [email protected]
[mailto:[email protected]] Per conto di David Colignon
Inviato: giovedì 24 ottobre 2013 13.02
A: Umberto Iemma; [email protected]
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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