Meshing software

Mesh generators, CAD programs, and other tools
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mark smith
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Meshing software

Post by mark smith »

Hi,
I have recently become aware of coreform's CUBIT software https://coreform.com/ which is available for free for meshes up to 50000 elements, it is from the CUBIT stable so should be quite powerful, I was wondering if there are any Elmer users who use CUBIT for their meshing process and if so what procedure do they use to get their mesh into Elmer?
Regards
Mark
raback
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Re: Meshing software

Post by raback »

Hi

This seems to be the listing of their formats:
https://coreform.com/cubit_help/cubithe ... _model.htm

Not too open source friendly. Maybe you could ask them directly. The seem not to be associated to any FEM code so they could be positive towards open source.

-Peter
kevinarden
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Re: Meshing software

Post by kevinarden »

Like most pre-processors the have an export function, checking their documentation they export an ABAQUS file or a Universal file, both of the formats are converted to Elmer mesh using ElmerGrid.
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Re: Meshing software

Post by kevinarden »

I downloaded it and meshed a step file, it did a very good job of automatically create a brick mesh on the step part. I exported a universal and translated it using ElmerGrid which worked. One issue is that it did not create any boundary elements by default, which Salome does. Elmer uses boundary elements for restraints and loads.
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kevinarden
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Re: Meshing software

Post by kevinarden »

I went back to Cubit and plate meshed the outer surface, which matched nicely with the brick elements. Exported unv file and Elmer successfully imported with the plate elements as boundary elements.
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raback
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Re: Meshing software

Post by raback »

Hi

Excellent! The quads have nicer numerical properties than wedges also. You could use even "Element = p:3" here and MUMPS. That would probably get you superior accuracy compared to much denser linear wedge elements.

When you choose p-elements the matrix unfortunately does not usually become easier to solve hence the direct solver MUMPS.

-Peter
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Re: Meshing software

Post by Coreform_Greg »

Hi, Greg here from Coreform! We are friendly towards open-source solvers. We're unable to open-source Cubit (though we've looked into this quite extensively) because if we took out all the 3rd-party functionality that we can't open-source, Cubit would no longer be Cubit! But we certainly want to be friendly with open-source solvers -- we've contributed to ParaView (adding support for Bezier cells to visualize splines / IGA), libMesh (open-source FEM framework), MOOSE, and SEACAS/Exodus.

On that note, I would say that Cubit *natively* supports the open-source mesh format: Exodus. Exodus is part of the open-source "Sandia Engineering Analysis Code Access System" (SEACAS) project. Given Cubit's long history at SNL, it's probably no surprise that Cubit was developed primarily to build Exodus mesh files for SNL's simulation codes. I'm admittedly not as familiar with Elmer as I am other codes, but it should be fairly straightforward to support Exodus in Elmer if it's not already.

In my former life, I found Exodus to be quite powerful for analysis - that SEACAS link talks about the gluttony of utilities for Exodus, from domain-decomposition & domain-recomposition, to ASCII conversion, Matlab converters, a Python module, variable remapping, and more. Plus Exodus stores not only the mesh for the simulation, but also the simulation results... and it's natively supported by ParaView (by default ParaView applies the "warp vector" within its Exodus reader, and it even has a simple option to draw mode shapes if provided). In fact, while the format is technically called "Exodus" users will often refer to the input-mesh file as a "Genesis" file (note the biblical reference) and the output-mesh with results as "Exodus".

On the note of p-elements, we're also adding our U-spline technology to Coreform Cubit - which we plan to also make available in Coreform Cubit Learn. And Coreform Cubit will be able to export the Bezier extraction operator, which allows for a traditional FEM solver to access spline finite elements. So you could build a cubic U-spline, whose matrix is easier to solve (even easier than a linear element's global matrix).
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Re: Meshing software

Post by raback »

Hi Greg,

I think the Universal mesh format seems to be working already. It is not perfect mainly because it is missing the pyramids. Still it apparently provides a working workflow between the two codes.

It is ok for us that people combine open source and closed source. We are pragmatic. The business logic does not work that well for preprocessing as there are less soft funding opportunities available.

-Peter
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