[joaquinmorenou]

Hi , I'm meshing a cylinder in a flume that have a sandbox right below the cylinder and my problem is that when I use snappy some areas of the blockMesh mesh dissapear. In particular the 1st and the 2nd block. Right below i attached the blockMesh and SnappyHexMeshFile.


Hope you can help me

The cylinder stl : https://drive.google.com/file/d/1xei...ew?usp=sharing

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



convertToMeters     1.0;

vertices
(
    (0 0 0.08) //0
    (0.8 0 0.08) //1
    (0.8 0.6 0.08) //2
    (0 0.6 0.08) //3
    (0 0 0.16) //4
    (0.8 0 0.16) //5
    (0.8 0.6 0.16) //6
    (0 0.6 0.16) //7
    (0.32 0.22 0) //8
    (0.48 0.22 0) //9
    (0.48 0.38 0) //10
    (0.32 0.38 0) //11
    (0.32 0.22 0.08) //12
    (0.48 0.22 0.08) //13
    (0.48 0.38 0.08) //14
    (0.32 0.38 0.08) //15
    (0 0.22 0.08) //16
    (0.8 0.22 0.08) //17
    (0 0.38 0.08) // 18
    (0.8 0.38 0.08) // 19
    (0.32 0.22 0.16) // 20
    (0.48 0.22 0.16) // 21
    (0.48 0.38 0.16) // 22
    (0.32 0.38 0.16) // 23
    (0 0.22 0.16) // 24
    (0.8 0.22 0.16) // 25
    (0.8 0.38 0.16) // 26
    (0 0.38 0.16) // 27
);

blocks
(
    hex (0 1 17 16 4 5 25 24)  (160 44  16) simpleGrading (1 1 1)
    hex (18 19 2 3 27 26 6 7) (160 44 16) simpleGrading (1 1 1)
    hex (16 12 15 18 24 20 23 27) (64 32 16) simpleGrading (1 1 1)
    hex (12 13 14 15 20 21 22 23) (32 32 16) simpleGrading (1 1 1)
    hex (13 17 19 14 21 25 26 22) (64 32 16) simpleGrading (1 1 1)
    hex (8 9 10 11 12 13 14 15) (32 32 16) simpleGrading (1 1 1)
);
 
edges
(
);

patches
(
    patch inlet
    (
        (0 4 24 16)
        (16 24 27 18)
    (18 27 7 3)
    )
    patch outlet
    (
        (1 17 25 5)
    (17 19 26 25)
    (19 2 6 26)
    )
    symmetryPlane surface
    (
        (4 5 25 24)
    (27 26 6 7)
    (24 20 23 27)
    (20 21 22 23)
    (21 25 26 22)
    )
    wall bottom
    (
        (0 1 17 16)
        (18 19 2 3)
        (16 12 15 18)
    (13 17 19 14)
    (8 9 10 11)
        (0 1 5 4)
    (8 9 13 12)
    (11 8 12 15)
    (9 10 14 13)
        (3 7 6 2)
    (11 15 14 10)
    )
);

mergPatchPairs
(
);

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Which of the steps to run
castellatedMesh true;
snap            false;
addLayers       false; //pour ajouter des couches près des parois


// Geometry. Definition of all surfaces. All surfaces are of class
// searchableSurface.
// Surfaces are used
// - to specify refinement for any mesh cell intersecting it
// - to specify refinement for any mesh cell inside/outside/near
// - to 'snap' the mesh boundary to the surface
geometry
{
    Cylinder.stl
    {
        type triSurfaceMesh;
        name cylinder;
    }
        surface1
    {
        type searchableBox;
        min (-1 -1    -0.1 );
        max (1   1     0.2);
    }
};


castellatedMeshControls
{

    maxLocalCells 1000000;


    maxGlobalCells 4000000;

    minRefinementCells 0;

    maxLoadUnbalance 0.10;

    nCellsBetweenLevels 3;

    features
    ();

    refinementSurfaces
    {
        cylinder
        {
            level (1 1);
        }
    }

    resolveFeatureAngle 30;

    refinementRegions
    {   
    }

    locationInMesh (0.300001 0.24 0.12);


    allowFreeStandingZoneFaces true;
}



snapControls
{
    nSmoothPatch 3;

    tolerance 2.0;

    nSolveIter 30;

    nRelaxIter 5;

}

addLayersControls
{
   relativeSizes false;

    layers
    {
        "(cylinder).*"
        {
            nSurfaceLayers 20;// nb de couches à ajouter prés des parois
        }
    }

    expansionRatio 1.19;
    finalLayerThickness 0.00002;
    minThickness 0.00000001;

    nGrow 0;


    featureAngle 60;

    nRelaxIter 5;

    nSmoothSurfaceNormals 1;

    nSmoothNormals 3;

    nSmoothThickness 10;

    maxFaceThicknessRatio 0.5;

    maxThicknessToMedialRatio 0.3;

    minMedianAxisAngle 90;


    nBufferCellsNoExtrude 0;


    nLayerIter 50;

}



meshQualityControls
{
    maxNonOrtho 65;

    maxBoundarySkewness 20;
    maxInternalSkewness 4;

    maxConcave 80;

    minVol 1e-13;

    minTetQuality 1e-30;

    minArea -1;

    minTwist 0.05;

    minDeterminant 0.001;

    minFaceWeight 0.05;

    minVolRatio 0.01;

    minTriangleTwist -1;


    nSmoothScale 4;
    errorReduction 0.75;
}



debug 0;


mergeTolerance 1e-6;


// ************************************************************************* //

[Swift]

Hi Joaquinmorenou,


Your mistake is in your blockMesh file. You need to build up the blockMesh shape using shared vertices to tell blockMesh that it is one shape. If you decide to do this, I estimate that you need 36 vertices and 10 blocks definitions.


The easier way of solving your problem is to make an stl shape of your geometry and put that into a bigger blockmesh cube with one block and run snappy.



Thomas


p.s. next time show images of the problem or upload a minimal case that the community can just run. This will help you get answers quicker. I had to make a case to test for you.