FEM Mesh Export

[tcsut]

So far I was using freecad 0.18.
I played with the electrostatic two ball example in freecad 0.19.

When I define mesh groups for all the boundaries small_sphere1 and small_sphere2, do the meshing, export the mesh in TwoBallsExport.unv-file and load the file in elmergui, one of the sphere boundaries is not available anymore.

TwoBallPic1.PNG (47.48 KiB) Viewed 2078 times

TwoBallPic2.PNG (130 KiB) Viewed 2078 times

On the other hand if use the original ball example in freecad 0.19 and execute the write button in the SolverElmer task. Afterwards I loaded the generated mesh.unv-file into elmergui, which contains all boundaries (taken from the constraints).

TwoBallPic3.PNG (96.46 KiB) Viewed 2078 times

I attached mesh.unv and TwoBallsExport.unv in the TwoBalls.zip
What is the difference? What do I need to do (region, boundary, group) to get the same .unv file with a manual mesh export?
Thanks for any hints!

[tcsut]

Now I found out if I use ElmerGrid command:
ElmerGrid 8 2 TwoBallsExport.unv -autoclean

which generates TwoBallsExport folder out of the imported unv file, contains all boundaries as expected

[bernd]

great you found a solution.

BTW: Welcome to FreeCAD FEM forum.

cheers bernd

[HoWil]

Now I found out if I use ElmerGrid command:
ElmerGrid 8 2 TwoBallsExport.unv -autoclean

which generates TwoBallsExport folder out of the imported unv file, contains all boundaries as expected

Hi tcsut,
Do I see it right, that it is possible to import an .sif and the connected unv into ElmerGui recently.
Did not know that. If so many things are becoming easier.
Br

[tcsut]

Hi HoWil

My understanding of ElmerGrid is that there are some compatibility issues with the .unv format FreeCAD is exporting.
There should be some experts around, who can explain that more elaborate.

I prefere generating the mesh with FreeCAD and exporting it to ElmerGui to have more control of the workflow.
With ElmerGrid you could also convert (and -autoclean) it into a .msh file:

Code: Select all

ElmerGrid 8 4 TwoBallsExport.unv -autoclean

[HoWil]

My understanding of ElmerGrid is that there are some compatibility issues with the .unv format FreeCAD is exporting.

Do you experience any issues or do you simply want to indicate that there could be some issues? Please see also https://forum.freecadweb.org/viewtopic. ... nv#p195056

There should be some experts around, who can explain that more elaborate.

I prefere generating the mesh with FreeCAD and exporting it to ElmerGui to have more control of the workflow.
With ElmerGrid you could also convert (and -autoclean) it into a .msh file:

Code: Select all

ElmerGrid 8 4 TwoBallsExport.unv -autoclean

ping

[bernd]

My understanding of ElmerGrid is that there are some compatibility issues with the .unv format FreeCAD is exporting.
There should be some experts around, who can explain that more elaborate.

FYI: FreeCAD uses Salome SMESH library to export the unv.

[raback]

Hi

UNV format is certainly too complicated to be fully parsed with any reasonable effort: Hundreds of fields annoying layout. Our strategy for ElmerGrid has been to use samples and make them work. When the set of samples is large enough the odds that the next case would also work increases.

The UNV files so far have mainly come from HyperMesh and Salome. FreeCAD may use partly different fields. Hence if you have a non-working UNV file please make a minimal sample of it and sent it to me.

-Peter

[bernd]

Hi

UNV format is certainly too complicated to be fully parsed with any reasonable effort: Hundreds of fields annoying layout. Our strategy for ElmerGrid has been to use samples and make them work. When the set of samples is large enough the odds that the next case would also work increases.

The UNV files so far have mainly come from HyperMesh and Salome. FreeCAD may use partly different fields. Hence if you have a non-working UNV file please make a minimal sample of it and sent it to me.

-Peter

As said FreeCAD uses Salome SMESH code to export unv. Means A unv mesh exported from Salome and from FreeCAD should be identical!

[raback]

Ok. Elmer should then be able to read most of the meshes but there can always be some exception. Still it is a good idea to sent the non-working example.

Btw, it is pretty alarming that it seems to be very difficult to find the UNV standard online. While googling a few minutes many of the old links seemed to be dead and the only document I was able to find was this one from 1987.

https://www.google.com/url?sa=t&rct=j&q ... TXlLGeCLVE

It would really be nice if there was some proper standard that does not assume fixed format with 80 character lines

-Peter