[Gmsh] Help understanding MSH file entries while using "Periodic surface with translate "

[Ranga Sudarsan]

Hi Guillaume,
   yes I have looked at the documentation to understand it but I cannot 
understand it fully though.

The entries for the point entity  inside the $Periodic  I think I 
understand (please correct me If I am wrong?).
For example:
0 8 1   //  0 indicating it is point, 8 and 1 are slave and master tag 
entity
Affine 1 0 0 5 0 1 0 0 0 0 1 0 0 0 0 1  // indicating the Affine 
transformation to go from master to slave
1    // Number of entities
8 1 // slave node number, master node number

For the Line entity Inside $Periodic I have for example
1 12 2  // 1 indicating it is a line , Not clear what 12 and 2 
correspond to as they are not corresponding node numbers
Affine 1 0 0 5 0 1 0 0 0 0 1 0 0 0 0 1
43  // Number of nodes
xx  xx   // Matching node numbers

I cannot seem to understand 12 and 2 in the first line after 1 as 12 and 
2 are not corresponding point/node numbers on the master and slave surfaces.

Likewise for the Surface entity inside $Periodic I have for example

2 8 1  // 2 indicating it is a surface, Not clear what 8 and 1 are
Affine 1 0 0 5 0 1 0 0 0 0 1 0 0 0 0 1
3511  // Number of matched nodes between master and slave surfaces
xx  xx

Hope this clarifies my question better.

Thanks again for the help


On 27/04/2017 7:20 AM, DILASSER Guillaume wrote:
>
> Hi,
>
> Have you looked at the documentation here 
> <http://gmsh.info/doc/texinfo/gmsh.html#MSH-ASCII-file-format> ? It says :
>
> /$Periodic/
>
> /number-of-periodic-entities/
>
> /dimension slave-entity-tag master-entity-tag/
>
> /number-of-nodes/
>
> /slave-node-number master-node-number/
>
> /…/
>
> /$EndPeriodic/
>
> It looks like your information.
>
> Faithfully Yours,
>
> Guillaume DILASSER
>
> Doctorant SACM / LEAS
>
> CEA - Centre de Saclay - Bât.123 - PC 319c
>
> 91191 Gif sur Yvette Cedex - France -
>
> guillaume.dilasser at cea.fr <mailto:guillaume.dilasser at cea.fr>
>
> *De :*gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] *De la 
> part de* Ranga Sudarsan
> *Envoyé :* jeudi 27 avril 2017 12:56
> *À :* gmsh mailing list <gmsh at onelab.info>
> *Objet :* [Gmsh] Help understanding MSH file entries while using 
> "Periodic surface with translate "
>
> Hi there,
>     I am meshing a geometry with periodic (translated meshes) boundary 
> conditions along one of the directions (X in my case). I am using
> periodic surface with translate to setup the translated periodic 
> meshes. I need help understanding some entries in the Msh file 
> generated specifically the section under "$Periodic" (See attached 
> image, in my case surfaces 1 and 8 are periodic). I understand that in 
> my case their are totally 11 periodic entities -- 5 points , 5 lines 
> and 1 surface and my trouble is in understanding the format of the 
> output corresponding to each of these periodic entities. It will be of 
> great help if some one explain to me what is the format for each of 
> these entities so that I can write a code to read the msh file and 
> generate relevant input files for my finite element solver. I have 
> attached the geo and mesh file.
>
> Thanks again
> Ranga Sudarsan
>

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