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-   -   Problem with tetrahedral-mesh (salome) (http://www.cfd-online.com/Forums/openfoam-meshing-open/98550-problem-tetrahedral-mesh-salome.html)

matthiass March 13, 2012 13:02

Problem with tetrahedral-mesh (salome)
 
3 Attachment(s)
Hello everybody,

I'm new to OpenFOAM and I want to use CAD-Data meshed with Salome in OpenFOAM. For learning how to use OpenFOAM with structural mechanics I used a simple model. It is a simple beam, which is fixed at the bottom and displaced (0.04m in y-direction) at the upper part.

I tried the import (ideasUnvToFoam) of a hexahedral and a tetrahedral mesh with the complete same case. The hex-mesh worked fine and with the tet-mesh I get really strange results which I can't explain (see pics). checkMesh does not complain after the import of the tet-mesh.
Unfortunaley the mesh-size is to big, so i could not upload it.

I would be very thankful if someone could help me!

Best regards
Matthias

matthiass March 14, 2012 06:38

Hello all,

is there anybody out there, who had a comparable problem or has anybody an idea where I can start searching.
I already checked my mesh with checkMesh and the solver converged as well.


Another question I have is:
one of my boundary conditions is a displacement of 0.04m:
oben
{
type fixedValue
value uniform (0 0.04 0)
}

Now I want that the motion in x- and z-direction is not "0" but changes, so that the boundary "oben" isn't anymore parallel to its initial position. Is there an easy way to do this?.

With best regards
Matthias

Locky3827 March 15, 2012 18:20

Hi,
I've had a similar issue in fluid dynamics in laminar pipe flow of non-Newtonian fluids. With hex meshes developed using blockMesh I get converged solutions which agree very well for the pressure drop with the analytical values. With tet meshes with viscous layers developed in Salome, the pressure drop is about 5% too high even though the solutions are well converged. I'm working through some possible issues with mesh quality and choice of discretisation schemes etc. Perhaps these will help. I want to move to more complex gemetries so I need to validate the meshing.
Not sure if I have helped, but perhaps there is an issue.
Regards,
Lachlan

matthiass March 19, 2012 05:23

Hello Lachlan,

thank you for your reply! Until now I haven't found a solution for my problem. But I'm still working on it. As alternativity I'm testing snappyHexMesh, because I want to move to more complex geometries, too.

Best regards
Matthias

kmooney March 20, 2012 10:59

Eric Patterson gives some good recommendations for discretization choices for unstructured grids in this Thread (post #5).

http://www.cfd-online.com/Forums/ope...red-grids.html

It might improve your solution.

matthiass March 20, 2012 15:52

Hi kmooney,

thank you for the link. It sounds interesting and I will try it!

Best regards
Matthias


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