[maka15]

Hi,
I'm quite new to openfoam and I am seeing a strange behavior on a very simple blockMesh I want to use for snappyHexMesh..
It is just a cuboid with cube-cells, but when I view the Mesh with paraView, I see very strange cells, that I can't explain. I only see them in the middle of the block in the XZ-Plane. Attached you find an image of ParaView showing these strange cells, if you want to reconstruct using the Dicts below, create a slice in ParaView, click "Y normal" and don't move the plane...
Would be nice, if someone here has an idea, what I am doing wrong..

Thanks a lot for your help!

system/blockMeshDict

FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object blockMeshDict;
}

    convertToMeters 1;
    vertices  
    (
      ( -0.02 -0.02 -0.032)
      ( 0.02 -0.02 -0.032)
      ( 0.02 0.02 -0.032)
      ( -0.02 0.02 -0.032)
      ( -0.02 -0.02 0.013)
      ( 0.02 -0.02 0.013)
      ( 0.02 0.02 0.013)
      ( -0.02 0.02 0.013)
    );
    blocks  
    ( 
      hex ( 0 1 2 3 4 5 6 7) ( 80 80 90)
      simpleGrading ( 1 1 1)
    );
    edges  
    (
    );
    patches  
    (
    );
    mergePatchPairs  
    (
    );

system/controlDict

FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object controlDict;
}

    startFrom startTime;
    startTime 0;
    stopAt endTime;
    endTime 1000.0;
    deltaT 1.0;
    writeControl timeStep;
    writeInterval 1000.0;
    purgeWrite 0;
    writeFormat ascii;
    writePrecision 100;
    writeCompression uncompressed;
    timeFormat general;
    timePrecision 6;
    graphFormat raw;
    runTimeModifiable yes;

system/fvSchemes (only so paraFoam does not warn about missing files..)

FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object fvSchemes;
}

    divSchemes
    {
    }

    gradSchemes
    {
    }

    laplacianSchemes
    {
    }

system/fvSolution (only so paraFoam does not warn about missing files..)

FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object fvSolution;
}

    solvers
    {
    }

[Antimony]

Hi,

Do a checkMesh and see the type of cells that it reports. My guess is that it will still be hexes.

The reason you see the weird cells is because Paraview decomposes polyhedral cells automatically and when you take a slice, it triangulates the slice. Uncheck both options and you will see that they are regular hexes only.

Cheers,
Antimony

[maka15]

Hi,

thanks for your help, Antimony!

checkMesh reports only hexes, you are right.

If I uncheck decomposing and triangulating, it does look better, but still weird, see attached image.

@Mods: It seems, this is more likely a problem with paraView than with blockMesh, could you please move the thread to the right subforum?

[Flowkersma]

Hi,

Try using ExtractCellsByRegion filter when you want to visualize the mesh. If you want slice like behavior check Extract only intersected and Extract intersected marks. If you compare the results from ExtractCellsByRegion filter to the results of Slice filter, maybe you can find a reason for the "strange" behavior.

Regards,
Mikko