Including a new element in ElmerFem

The graphical user interface of Elmer

Including a new element in ElmerFem

Postby sharath » 10 Aug 2017, 09:14

I just wanted to include some of the elements that are not available in the Elmer Architecture.

If i want to do so,

Do i need to change the code: In ElmerGrid / In the Application folder of ElmerGUI / in both of them.
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Re: Including a new element in ElmerFem

Postby annier » 11 Aug 2017, 09:56

Hi sharath,
Please be specific on what you mean by "the elements that are not available in the Elmer Architecture".
If you are talking on adding new solvers, then you do not need to change the available codes. For this case or context, you need to :
1. Write the new solver in accordance to chapter 2 of Elmer Programmer's Tutorial (http://www.nic.funet.fi/pub/sci/physics ... torial.pdf).
2. Compile the solver in your user directory with elmerf90 fortran compiler as mentioned in the same chapter. The resultant file is a shared object (so) [linux] or dll file [windows] file.
3. Put your solver input file in the same directory as the new solver shared object or dll file. You can call this solver using the calling convention of Elmer Solver.
4. I am describing these steps from the viewpoint of Ubuntu linux and non GUI user. In context of windows, an experienced windows user and/or a GUI user can describe you more.


Yours Sincerely,
Anil Kunwar
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Re: Including a new element in ElmerFem

Postby raback » 11 Aug 2017, 10:46

Hi sharath

Please could you specify what you mean with a "new element".

The answer is very different if you need a mathematically new element, or just an implementation of a new equation (which would be a new element in Ansys terminology, for example, but would not really introduce new basis functions).

-Peter
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Re: Including a new element in ElmerFem

Postby sharath » 16 Aug 2017, 14:57

I have a problem in importing Gmsh mesh file in to ElmerGUI.
So, I wanted to find the way to include the 27 node Hexahedron element for which ElmeGrid or ElmerGUI are not able to detect the boundaryb surfaces.
So, I wanted to find what is making the Elmer not to detect the surfaces of 27 node Hexahedron element.
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Re: Including a new element in ElmerFem

Postby raback » 16 Aug 2017, 15:40

Hi

27 node hexahedron is supported by ElmerSolver but obviously something goes wrong in the translation into Elmer format. Usually this is different ordering schemes.

Maybe you could share a minimalistic .msh file for debugging.

-Peter
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Re: Including a new element in ElmerFem

Postby sharath » 17 Aug 2017, 11:24

I am uploading the 27 node hexahedron element created by gmsh in the following file for Debugging.

27node.msh
(1.36 KiB) Downloaded 7 times


Please try to check why ElmerGrid and ElmerGUI are unable to detect the surfaces of the volume.

Thanking you,

With Regards,

Sharath
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Re: Including a new element in ElmerFem

Postby raback » 17 Aug 2017, 15:20

Hi

The quadratic hexahedron (type 827 in Elmer) should now be better supported by stand-alone ElmerGrid. The fix was committed minutes ago and will migrate to exucutables eventually.

ElmerGUI was not yet affected as the codes of ElmerGrid and ElmerGrid plug-in of ElmerGUI have unfortunately forked and should be reharmonized again. So if you have problems in ElmerGUI you can always still try with the command-line tool.

Thanx for reporting!

-Peter
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Re: Including a new element in ElmerFem

Postby sharath » 17 Aug 2017, 19:55

Mr. Peter,

Thanking for considering my request. With ignorance, I am asking one question that, What do you mean by Stand-alone ElmerGrid.




If I am using ElmeGrid Stand-alone. Its creating the surfaces but when importing to GUI, I am facing following problem

***********************************************************************************************************************************************
Loading from directory /home/sharath/Desktop/27node
Loading elmer mesh files
Summary:
Nodes: 27
Point elements: 0
Edge elements: 0
Surface elements: 6
Volume elements: 1
Found 12 edges on boundary
findSurfaceElementNormals: error: unable to change element orientation
**************************************************************************************************************************************************

Can we work solver of ElmerSolver (like applying Boundary conditions, Traction forces on surfaces and body forces) using Command line tool. If so, Can you please suggest any reference to work with command-line tool.

Sharath.
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Re: Including a new element in ElmerFem

Postby mzenker » 18 Aug 2017, 00:22

Hi,

ElmerGrid is the program described in the ElmerGrid manual. It is run from the command line (DOS box or Linux terminal), takes a mesh file (e.g. in gmsh format) as input and several files for the mesh in Elmer format. ElmerSolver needs those to run. The functionality of ElmerGrid is included in ElmerGUI, so you can do File->Open on a .msh file, for example. Sometimes ElmerGUI cannot digest a mesh file, but ElmerGrid can. In those cases, you can convert the mesh file on the command line and do File->Load mesh in ElmerGUI, so the Elmer mesh files are loaded directly.
If that also fails, you can still use ElmerGUI to make a sif file (using a dummy mesh) and call ElmerSolver from the command line. Or you can edit the sif file with a text editor and work without ElmerGUI.

HTH,

Matthias
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