[Gmsh] periodic pairs of internal nodes of each edge

[Koen Hillewaert (Cenaero)]

Hi all,

in my opinion, this correspondence should not be stored since it can be 
deduced straightforwardly from the principal vertices. In general, I 
think we should limit the data in the file without incurring a huge cost 
to reconstruct missing information or even risk ambiguities - both are 
applicable to periodic transformations; storing only principal vertices 
then seems the best compromise. The compacity of this section is 
important, since periodicity information is very difficult to partition, 
which means that this section should be as light as possible as it is 
duplicated for all partitions in case we store one file per partition - 
the latter option is important for very large meshes.

The ho point correspondence is stored in gmsh internal datastructures 
though, since it is required for ensuring continued periodicity when 
optimizing a high order mesh - we guarantee that the high order nodes 
also satisfy exactly the periodicity. In principle, adding these points 
should therefore not require a big effort.

This being said, there is currently an issue with reading periodic 
meshes : gmsh seems to displace the nodes by twice the periodicity 
transformation.

Best,

Koen


On 07/26/2018 07:34 PM, Christophe Geuzaine wrote:
>
>
>> On 26 Jul 2018, at 08:24, Nan Li <linan88433189 at gmail.com 
>> <mailto:linan88433189 at gmail.com>> wrote:
>>
>> Hello everyone,
>>
>> I am trying to mesh a cross-cavity with high order tetrahedron 
>> element (tetrahedron 10) and apply periodic boundary condition in x 
>> direction and y direction. As the periodic boundary condition has 
>> nothing to do with the cavity,  you can consider the cross-cavity as 
>> a cube.
>>
>> I have used 'periodic surfaces' and find the mesh of the two opposite 
>> surface is identical. So far so good. Then when I look into the .msh 
>> file and try to extract the point pairs in $Periodic $EndPeriodic, I 
>> find that only the nodes on the vertex of triangle are listed there. 
>> The internal nodes for each edge are not listed.
>>
>> Does anyone have successfully extract the periodic pairs of internal 
>> nodes of each edge ?
>>
>
> Indeed we only keep track of the main vertices in the Periodic 
> section. Once you have those you can get the element correspondance 
> and match the high-order ones.
>
> @Koen, Amaury - should we also add the high-order vertices in the 
> correspondance tables ?
>
> Christophe
>
>
>> Thanks.
>>
>> Nan LI
>> <cross_cavity.geo>_______________________________________________
>> gmsh mailing list
>> gmsh at onelab.info <mailto:gmsh at onelab.info>
>> http://onelab.info/mailman/listinfo/gmsh
>
> —
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine 
> <http://www.montefiore.ulg.ac.be/%7Egeuzaine>
>
> Free software: http://gmsh.info | http://getdp.info | http://onelab.info
>

-- 
Koen Hillewaert
Fluid Dynamics Technology Leader

https://www.researchgate.net/profile/Koen_Hillewaert

Cenaero
Your R&T partner in modeling and numerical simulation

Tel: + 32 (0)71  910 942
Fax: + 32 (0)71  910 931
Mob: + 32 (0)495 385 030
Skype: koen.hillewaert.cenaero

Cenaero
Rue des Frères Wright, 29
6041 Gosselies
Belgium

Visit our web site: www.cenaero.be

+-+-+- www.cenaero.be/disclaimer +-+-+-

Please consider the environment before printing this e-mail.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://onelab.info/pipermail/gmsh/attachments/20180726/e21c2860/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: per_channel.msh
Type: model/mesh
Size: 9893 bytes
Desc: not available
URL: <http://onelab.info/pipermail/gmsh/attachments/20180726/e21c2860/attachment-0001.msh>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: koen_hillewaert.vcf
Type: text/x-vcard
Size: 381 bytes
Desc: not available
URL: <http://onelab.info/pipermail/gmsh/attachments/20180726/e21c2860/attachment-0001.vcf>