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-   -   [STL->GMSH->simpleFoam] (http://www.cfd-online.com/Forums/openfoam-meshing-open/112237-stl-gmsh-simplefoam.html)

huitetquatre January 24, 2013 09:28

[STL->GMSH->simpleFoam]
 
Hi,

I'm looking for a simple example in which:
- the mesh is generated with gmsh using an STL object;
- the computation is made with simpleFoam.

In practice, my attempts always lead to a "Floating point exception"...

wyldckat January 24, 2013 17:34

Greetings David,

Have you tried to replicate one of OpenFOAM's tutorials for simpleFoam, but using a mesh generated with Gmsh?

Have you checked the validity of your mesh after conversion? Try:
Code:

checkMesh
checkMesh -allGeometry -allTopology

Best regards,
Bruno

huitetquatre January 25, 2013 06:37

In fact, the simple "checkMesh" is Ok, the Topology (-allTopology) is also OK, but the the geometry check (-allGeometry) failed.

How can I modify the gmsh file to solve this kind of problem ?

Code:

>    Face tets OK.
>    Min/max edge length = 0.168466 10.198 OK.
>    All angles in faces OK.
>    All face flatness OK.
>    Cell determinant (wellposedness) : minimum: 0 average: 1.34053
>  ***Cells with small determinant found, number of cells: 646
>  <<Writing 646 under-determined cells to set underdeterminedCells
>    Concave cell check OK.


wyldckat January 26, 2013 15:51

Hi David,

Mmm... cell determinant zero can lead to some problems... Run the following command:
Code:

foamToVTK -cellSet underdeterminedCells
Then open the file "underdeterminedCells*.vtk" which should be inside the folder "VTK". It will show you where the cells with very small determinant are located.

edit: sorry, I forgot to mention that once you see the bad cells, you try and increase refinement or orientation on the zone where those cells are having problems.

Best regards,
Bruno


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