GMSH meshing-vtk file output-Unit of measure

[Milo]

I members,

I try to work with elmer but I can't do these things:

1) Meshing a .step file (I try to use also gmsh but I take this message:‎[Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)

2) Define Unit of measure (I read elmer forum but I don't understand the solution

3) export .vtk file to use paraview post-processing

I hope you can help because I can't take solution.

Best Regards,
Stefano

[mzenker]

Hi,

1) This is a currently unsolved problem for 3D geometries with adjacent bodies. You may try to check "cut and merge faces" under Options->geometry in gmsh before opening the STEP file. This helps in simple cases. Depending on your geometry you may also save it in gmsh format (.geo) and try to repair it manually. Or you define it in gmsh directly, which quickly gets tedious since gmsh has very limited CAD capabilities.

2) Elmer doesn't assume a special set of units. Units have to be consistent, though - SI is always a good choice. If your geometry is in mm you should write "Coordinate Scaling = 0.001" into the free text field in the simulation section of Model->Setup in ElmerGUI.

3) Use the ResultOutput solver, see Models manual.

HTH,

Matthias

Edit: there were some typos.

[Milo]

ok for point 2 and 3.

For the first point, I use GMSH because the elmer don't mesh my .Step file.
I already try to use cut and merge but I don't resolve the problem.

Why elmer don't mesh my step model?

Thank you for your fast response.

Best Regards
Stefano

[mzenker]

Hi,

Elmer's meshing capabilities are rather limited. It is recommendable to use an external mesher.
What kind of geometry do you try to mesh?

Matthias

[Milo]

I create a simple frame to try to use elmer.

I try to use also netgen but I take an error message when opens.
And I try to compile tetgen without success.

I know that this is a problem already discussed but reading this forum I can't solve it.

Stefano

[raback]

Hi

ElmerGUI does not support multi-domain CAD geometries in import. Can you load that in netgen directly?

-Peter

[Milo]

When I open netgen I obtain this message.

Thanks

Stefano

[mzenker]

Hi,

if netgen cannot heal your geometry, you can in principle repair it manually in gmsh, but it's tedious since there are many volumes and interfaces.
You can also test GiD, which is a low-cost commercial mesher with a one-month free (but a bit limited) test licence, and may be more powerful than gmsh.
Salome is another powerful free mesher. Its healing algorithm is said to be imported in gmsh, but I suspect that this import doesn't work correctly (yet).
Both GiD and Salome require a certain learning curve, but there are people out there who prefer them over gmsh and netgen.

Matthias

[Milo]

I see that GiD is much expensive.

I try to use Salome.... thanks to everybody.

[mzenker]

Remark, if you work under Windows: The Windows version of Salome was said to be experimental some time ago. Don't know if this has changed in the meantime.

Matthias