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-   OpenFOAM Meshing & Mesh Conversion (https://www.cfd-online.com/Forums/openfoam-meshing/)
-   -   [snappyHexMesh] snapEdge - failure (https://www.cfd-online.com/Forums/openfoam-meshing/84449-snapedge-failure.html)

hfs October 31, 2012 06:33
Thank you!

niklas October 31, 2012 06:37
Quote:
Originally Posted by hfs (Post 389439)
Is this here the secret?: [faceType boundary;]
In blockMesh: Is creating one patch for all other patches as an empty patch is better for snapping?? Why??
No, faceType boundary shouldn't matter. I think the secret is in the blockMeshDict.
If you get this behaviour again, try adding/reducing the number of cells in one direction with 1.

I use snappy mostly for internal flows and then the patches doesnt matter.
Thats why. you can safely change the patches to whatever you want.

hfs October 31, 2012 07:39
Thanks again!

hfs November 13, 2012 11:23
2 Attachment(s)
Hello Niklas!

After getting the nicer mesh I am trying to simulate the wind pressure on my Umbrella...

I am getting crazy results on this Umb Patch [See attached pic] although the calculations seem correct if took a slice [attaches a pic as well]

So I used a faceZone and created two patches out of it ... the problem continues ...

this is how the boundary file will look like after modification:

Code:
7
(
    inlet
    {
        type            patch;
        nFaces          1000;
        startFace      402070;
    }
    outlet
    {
        type            patch;
        nFaces          1000;
        startFace      403070;
    }
    bottomWall
    {
        type            wall;
        nFaces          4632;
        startFace      404070;
    }
    topWall
    {
        type            wall;
        nFaces          3750;
        startFace      408702;
    }
    frontAndBack
    {
        type            symmetryPlane;
        nFaces          3000;
        startFace      412452;
    }
    Umb1
    {
        type            wall;
        nFaces          1066;
        startFace      415452;
    }
    Umb2
    {
        type            wall;
        nFaces          1066;
        startFace      416518;
    }
 
)
[Q]: How can I control the orientation of my faces ... and then how can I make 2 patched depending on the orientation so that I insure that Umb1 is Upper and Umb2 is Lower?
[Q]Is there another way to do that?

Please see this thread for more details..
http://www.cfd-online.com/Forums/ope...nd-tunnel.html

________________________________________________

[P.s]: How serious are the errors in checkMesh:
Code:
<<Writing 21 conflicting points to set nonManifoldPoints
and
Code:
***Max skewness = 6.6003492, 8 highly skew faces detected
________________________________________________

Really appreciate your advice

hfs November 13, 2012 11:29
Here I have uploaded my Meshing Case and Simulation Case

http://dl.dropbox.com/u/32336583/How...Patches.tar.gz

Please take a look

Thanks!

Haces April 15, 2013 09:42
Hi!

I am using snappyHexMesh with OF2.2 but the program never finish to do the snapping.

When it is snapping I always get a warning message: "FOAM Warning : Displacement () at mesh point '*' coord () points through the surrounding patch faces". After that the program moves the mesh. Sometimes the program is not successful and writes: "Did not succesfully snap mesh. Giving up."

I've tried a lot of combinations with the parameters inside the snapyHexMeshDict and I've also changed the blockMeshDict as niklas said, without success.

The .eMesh archive is correct. I've created an .obj file and I've seen it in paraview.

Here you have an example:

Code:
FOAM Warning : Displacement (-0.02266843 0.001091078 0.002192178) at mesh point 5161178 coord (1007.063 -66.16199 -0.003698507) points through the surrounding patch faces
Smoothing displacement ...
Iteration 0
Iteration 10
Displacement smoothed in = 64.32 s


Moving mesh ...

Iteration 0
Moving mesh using diplacement scaling : min:1  max:1
Checking faces in error :
    non-orthogonality >  65 degrees                        : 1525
    faces with face pyramid volume <    0                : 559
    faces with face-decomposition tet quality < 1e-30      : 5309
    faces with concavity >  80 degrees                    : 9
    faces with skewness >  4 (internal) or  20 (boundary) : 1
    faces with interpolation weights (0..1)  <  0.02      : 1
    faces with volume ratio of neighbour cells <  0.01    : 5
    faces with face twist <  0.02                          : 2
    faces on cells with determinant < 0.001                : 0

[...]

Iteration 9
Moving mesh using diplacement scaling : min:0  max:1
Checking faces in error :
    non-orthogonality >  65 degrees                        : 2
    faces with face pyramid volume <    0                : 0
    faces with face-decomposition tet quality < 1e-30      : 0
    faces with concavity >  80 degrees                    : 0
    faces with skewness >  4 (internal) or  20 (boundary) : 0
    faces with interpolation weights (0..1)  <  0.02      : 0
    faces with volume ratio of neighbour cells <  0.01    : 0
    faces with face twist <  0.02                          : 0
    faces on cells with determinant < 0.001                : 0
Moved mesh in = 235.15 s


Did not succesfully snap mesh. Giving up.
This is my blockMesh:

Code:
vertices
(
    (0    -67  -67)
    (1150  -67  -67)
    (1150  67  -67)
    (0      67  -67)

    (0    -67    67)
    (1150  -67    67)
    (1150  67    67)
    (0      67    67)
);

blocks
(
    hex (0 1 2 3 4 5 6 7) (40 5 5) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    maxY
    {
        type patch;
        faces
        (
            (3 2 6 7)
        );
    }
    minX
    {
        type wall;
        faces
        (
            (0 3 7 4)
        );
    }
    maxX
    {
        type wall;
        faces
        (
            (1 2 6 5)
        );
    }
    minY
    {
        type patch;
        faces
        (
            (0 1 5 4)
        );
    }
    minZ
    {
        type patch;
        faces
        (
            (0 1 2 3)
        );
    }
    maxZ
    {
        type patch;
        faces
        (
            (4 5 6 7)
        );
    }
);

mergePatchPairs
(
);
And my snappyHexMeshDict:

Code:
// Which of the steps to run
castellatedMesh true;
snap            true;
addLayers      false;




// 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
{
    water.stl
    {
        type triSurfaceMesh;
        name water;
    }



    //refinementBox
    //{
    //    type searchableBox;
    //    min (-0.3 -0.4 -0.1);
    //    max ( 3.0  0.4  1.4);
  // }
};



// Settings for the castellatedMesh generation.
castellatedMeshControls
{

    // Refinement parameters
    // ~~~~~~~~~~~~~~~~~~~~~

    // If local number of cells is >= maxLocalCells on any processor
    // switches from from refinement followed by balancing
    // (current method) to (weighted) balancing before refinement.
    maxLocalCells 1000000;

    // Overall cell limit (approximately). Refinement will stop immediately
    // upon reaching this number so a refinement level might not complete.
    // Note that this is the number of cells before removing the part which
    // is not 'visible' from the keepPoint. The final number of cells might
    // actually be a lot less.
    maxGlobalCells 20000000;

    // The surface refinement loop might spend lots of iterations
    // refining just a few cells. This setting will cause refinement
    // to stop if <= minimumRefine are selected for refinement. Note:
    // it will at least do one iteration (unless the number of cells
    // to refine is 0)
    minRefinementCells 0;

    // Allow a certain level of imbalance during refining
    // (since balancing is quite expensive)
    // Expressed as fraction of perfect balance (= overall number of cells /
    // nProcs). 0=balance always.
    maxLoadUnbalance 0.1;

    // Number of buffer layers between different levels.
    // 1 means normal 2:1 refinement restriction, larger means slower
    // refinement.
    nCellsBetweenLevels 3;



    // Explicit feature edge refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    // Specifies a level for any cell intersected by its edges.
    // This is a featureEdgeMesh, read from constant/triSurface for now.
    features
    (
      {
            file "water.eMesh";
            level 5;
        }

    );



    // Surface based refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~

    // Specifies two levels for every surface. The first is the minimum level,
    // every cell intersecting a surface gets refined up to the minimum level.
    // The second level is the maximum level. Cells that 'see' multiple
    // intersections where the intersections make an
    // angle > resolveFeatureAngle get refined up to the maximum level.

    refinementSurfaces
    {
        water
        {
            // Surface-wise min and max refinement level
            level (4 5);

            faceZone water;
            cellZone water;
            cellZoneInside inside;
        }


    }

    // Resolve sharp angles
    resolveFeatureAngle 87;


    // Region-wise refinement
    // ~~~~~~~~~~~~~~~~~~~~~~

    // Specifies refinement level for cells in relation to a surface. One of
    // three modes
    // - distance. 'levels' specifies per distance to the surface the
    //  wanted refinement level. The distances need to be specified in
    //  descending order.
    // - inside. 'levels' is only one entry and only the level is used. All
    //  cells inside the surface get refined up to the level. The surface
    //  needs to be closed for this to be possible.
    // - outside. Same but cells outside.

    refinementRegions
    {
      // refinementBox
      // {
        //    mode inside;
      //    levels ((1E15 4));
      // }
    }


    // Mesh selection
    // ~~~~~~~~~~~~~~

    // After refinement patches get added for all refinementSurfaces and
    // all cells intersecting the surfaces get put into these patches. The
    // section reachable from the locationInMesh is kept.
    // NOTE: This point should never be on a face, always inside a cell, even
    // after refinement.
    locationInMesh (500 42 42);


    // Whether any faceZones (as specified in the refinementSurfaces)
    // are only on the boundary of corresponding cellZones or also allow
    // free-standing zone faces. Not used if there are no faceZones.
    allowFreeStandingZoneFaces false;
}



// Settings for the snapping.
snapControls
{
    //- Number of patch smoothing iterations before finding correspondence
    //  to surface
    nSmoothPatch 10;

    //- Relative distance for points to be attracted by surface feature point
    //  or edge. True distance is this factor times local
    //  maximum edge length.
    tolerance 1.5;

    //- Number of mesh displacement relaxation iterations.
    nSolveIter 50;

    //- Maximum number of snapping relaxation iterations. Should stop
    //  before upon reaching a correct mesh.
    nRelaxIter 5;

    //- Highly experimental and wip: number of feature edge snapping
    //  iterations. Leave out altogether to disable.
    //  Of limited use in this case since faceZone faces not handled.
    //nFeatureSnapIter 15;

    // Feature snapping

        //- Number of feature edge snapping iterations.
        //  Leave out altogether to disable.
        nFeatureSnapIter 15;

        //- Detect (geometric only) features by sampling the surface
        //  (default=false).
        implicitFeatureSnap false;

        //- Use castellatedMeshControls::features (default = true)
        explicitFeatureSnap true;

        //- Detect points on multiple surfaces (only for explicitFeatureSnap)
        multiRegionFeatureSnap false;
}



// Settings for the layer addition.
addLayersControls
{
    relativeSizes false;

    // Per final patch (so not geometry!) the layer information
    layers
    {
        auto8
        {
            nSurfaceLayers 1;
        }
    }

    // Expansion factor for layer mesh
    expansionRatio 1.3;

    // Wanted thickness of final added cell layer. If multiple layers
    // is the thickness of the layer furthest away from the wall.
    // Relative to undistorted size of cell outside layer.
    finalLayerThickness 0.3036;

    // Minimum thickness of cell layer. If for any reason layer
    // cannot be above minThickness do not add layer.
    // Relative to undistorted size of cell outside layer.
    minThickness 0.005;

    // If points get not extruded do nGrow layers of connected faces that are
    // also not grown. This helps convergence of the layer addition process
    // close to features.
    // Note: changed(corrected) w.r.t 17x! (didn't do anything in 17x)
    nGrow 0;

    // Advanced settings

    // When not to extrude surface. 0 is flat surface, 90 is when two faces
    // are perpendicular
    featureAngle 30;

    // Maximum number of snapping relaxation iterations. Should stop
    // before upon reaching a correct mesh.
    nRelaxIter 3;

    // Number of smoothing iterations of surface normals
    nSmoothSurfaceNormals 1;

    // Number of smoothing iterations of interior mesh movement direction
    nSmoothNormals 3;

    // Smooth layer thickness over surface patches
    nSmoothThickness 2;

    // Stop layer growth on highly warped cells
    maxFaceThicknessRatio 0.5;

    // Reduce layer growth where ratio thickness to medial
    // distance is large
    maxThicknessToMedialRatio 1;

    // Angle used to pick up medial axis points
    // Note: changed(corrected) w.r.t 17x! 90 degrees corresponds to 130 in 17x.
    minMedianAxisAngle 90;

    // Create buffer region for new layer terminations
    nBufferCellsNoExtrude 0;

    // Overall max number of layer addition iterations. The mesher will exit
    // if it reaches this number of iterations; possibly with an illegal
    // mesh.
    nLayerIter 50;
}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
    //- Maximum non-orthogonality allowed. Set to 180 to disable.
    maxNonOrtho 65;

    //- Max skewness allowed. Set to <0 to disable.
    maxBoundarySkewness 20;
    maxInternalSkewness 4;

    //- Max concaveness allowed. Is angle (in degrees) below which concavity
    //  is allowed. 0 is straight face, <0 would be convex face.
    //  Set to 180 to disable.
    maxConcave 80;

    //- Minimum pyramid volume. Is absolute volume of cell pyramid.
    //  Set to very negative number (e.g. -1E30) to disable.
    minVol 0;

    //- Minimum quality of the tet formed by the face-centre
    //  and variable base point minimum decomposition triangles and
    //  the cell centre.  Set to very negative number (e.g. -1E30) to
    //  disable.
    //    <0 = inside out tet,
    //      0 = flat tet
    //      1 = regular tet
    minTetQuality 1e-30;

    //- Minimum face area. Set to <0 to disable.
    minArea -1;

    //- Minimum face twist. Set to <-1 to disable. dot product of face normal
    //- and face centre triangles normal
    minTwist 0.02;

    //- minimum normalised cell determinant
    //- 1 = hex, <= 0 = folded or flattened illegal cell
    minDeterminant 0.001;

    //- minFaceWeight (0 -> 0.5)
    minFaceWeight 0.02;

    //- minVolRatio (0 -> 1)
    minVolRatio 0.01;

    //must be >0 for Fluent compatibility
    minTriangleTwist -1;


    // Advanced

    //- Number of error distribution iterations
    nSmoothScale 4;
    //- amount to scale back displacement at error points
    errorReduction 0.75;
}


// Advanced

// Flags for optional output
// 0 : only write final meshes
// 1 : write intermediate meshes
// 2 : write volScalarField with cellLevel for postprocessing
// 4 : write current intersections as .obj files
debug 0;


// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1e-6;
I don't know what is wrong so if you have any idea how to fix it let me know.

Thanks!

David

hfs April 15, 2013 09:55
Quote:
Originally Posted by Haces (Post 420665)
Hi!

I am using snappyHexMesh with OF2.2 but the program never finish to do the snapping.

When it is snapping I always get a warning message: "FOAM Warning : Displacement () at mesh point '*' coord () points through the surrounding patch faces". After that the program moves the mesh. Sometimes the program is not successful and writes: "Did not succesfully snap mesh. Giving up."

I've tried a lot of combinations with the parameters inside the snapyHexMeshDict and I've also changed the blockMeshDict as niklas said, without success.

The .eMesh archive is correct. I've created an .obj file and I've seen it in paraview.

Here you have an example:

Code:
FOAM Warning : Displacement (-0.02266843 0.001091078 0.002192178) at mesh point 5161178 coord (1007.063 -66.16199 -0.003698507) points through the surrounding patch faces
Smoothing displacement ...
Iteration 0
Iteration 10
Displacement smoothed in = 64.32 s


Moving mesh ...

Iteration 0
Moving mesh using diplacement scaling : min:1  max:1
Checking faces in error :
    non-orthogonality >  65 degrees                        : 1525
    faces with face pyramid volume <    0                : 559
    faces with face-decomposition tet quality < 1e-30      : 5309
    faces with concavity >  80 degrees                    : 9
    faces with skewness >  4 (internal) or  20 (boundary) : 1
    faces with interpolation weights (0..1)  <  0.02      : 1
    faces with volume ratio of neighbour cells <  0.01    : 5
    faces with face twist <  0.02                          : 2
    faces on cells with determinant < 0.001                : 0

[...]

Iteration 9
Moving mesh using diplacement scaling : min:0  max:1
Checking faces in error :
    non-orthogonality >  65 degrees                        : 2
    faces with face pyramid volume <    0                : 0
    faces with face-decomposition tet quality < 1e-30      : 0
    faces with concavity >  80 degrees                    : 0
    faces with skewness >  4 (internal) or  20 (boundary) : 0
    faces with interpolation weights (0..1)  <  0.02      : 0
    faces with volume ratio of neighbour cells <  0.01    : 0
    faces with face twist <  0.02                          : 0
    faces on cells with determinant < 0.001                : 0
Moved mesh in = 235.15 s


Did not succesfully snap mesh. Giving up.
This is my blockMesh:

Code:
vertices
(
    (0    -67  -67)
    (1150  -67  -67)
    (1150  67  -67)
    (0      67  -67)

    (0    -67    67)
    (1150  -67    67)
    (1150  67    67)
    (0      67    67)
);

blocks
(
    hex (0 1 2 3 4 5 6 7) (40 5 5) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    maxY
    {
        type patch;
        faces
        (
            (3 2 6 7)
        );
    }
    minX
    {
        type wall;
        faces
        (
            (0 3 7 4)
        );
    }
    maxX
    {
        type wall;
        faces
        (
            (1 2 6 5)
        );
    }
    minY
    {
        type patch;
        faces
        (
            (0 1 5 4)
        );
    }
    minZ
    {
        type patch;
        faces
        (
            (0 1 2 3)
        );
    }
    maxZ
    {
        type patch;
        faces
        (
            (4 5 6 7)
        );
    }
);

mergePatchPairs
(
);
And my snappyHexMeshDict:

Code:
// Which of the steps to run
castellatedMesh true;
snap            true;
addLayers      false;




// 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
{
    water.stl
    {
        type triSurfaceMesh;
        name water;
    }



    //refinementBox
    //{
    //    type searchableBox;
    //    min (-0.3 -0.4 -0.1);
    //    max ( 3.0  0.4  1.4);
  // }
};



// Settings for the castellatedMesh generation.
castellatedMeshControls
{

    // Refinement parameters
    // ~~~~~~~~~~~~~~~~~~~~~

    // If local number of cells is >= maxLocalCells on any processor
    // switches from from refinement followed by balancing
    // (current method) to (weighted) balancing before refinement.
    maxLocalCells 1000000;

    // Overall cell limit (approximately). Refinement will stop immediately
    // upon reaching this number so a refinement level might not complete.
    // Note that this is the number of cells before removing the part which
    // is not 'visible' from the keepPoint. The final number of cells might
    // actually be a lot less.
    maxGlobalCells 20000000;

    // The surface refinement loop might spend lots of iterations
    // refining just a few cells. This setting will cause refinement
    // to stop if <= minimumRefine are selected for refinement. Note:
    // it will at least do one iteration (unless the number of cells
    // to refine is 0)
    minRefinementCells 0;

    // Allow a certain level of imbalance during refining
    // (since balancing is quite expensive)
    // Expressed as fraction of perfect balance (= overall number of cells /
    // nProcs). 0=balance always.
    maxLoadUnbalance 0.1;

    // Number of buffer layers between different levels.
    // 1 means normal 2:1 refinement restriction, larger means slower
    // refinement.
    nCellsBetweenLevels 3;



    // Explicit feature edge refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    // Specifies a level for any cell intersected by its edges.
    // This is a featureEdgeMesh, read from constant/triSurface for now.
    features
    (
      {
            file "water.eMesh";
            level 5;
        }

    );



    // Surface based refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~

    // Specifies two levels for every surface. The first is the minimum level,
    // every cell intersecting a surface gets refined up to the minimum level.
    // The second level is the maximum level. Cells that 'see' multiple
    // intersections where the intersections make an
    // angle > resolveFeatureAngle get refined up to the maximum level.

    refinementSurfaces
    {
        water
        {
            // Surface-wise min and max refinement level
            level (4 5);

            faceZone water;
            cellZone water;
            cellZoneInside inside;
        }


    }

    // Resolve sharp angles
    resolveFeatureAngle 87;


    // Region-wise refinement
    // ~~~~~~~~~~~~~~~~~~~~~~

    // Specifies refinement level for cells in relation to a surface. One of
    // three modes
    // - distance. 'levels' specifies per distance to the surface the
    //  wanted refinement level. The distances need to be specified in
    //  descending order.
    // - inside. 'levels' is only one entry and only the level is used. All
    //  cells inside the surface get refined up to the level. The surface
    //  needs to be closed for this to be possible.
    // - outside. Same but cells outside.

    refinementRegions
    {
      // refinementBox
      // {
        //    mode inside;
      //    levels ((1E15 4));
      // }
    }


    // Mesh selection
    // ~~~~~~~~~~~~~~

    // After refinement patches get added for all refinementSurfaces and
    // all cells intersecting the surfaces get put into these patches. The
    // section reachable from the locationInMesh is kept.
    // NOTE: This point should never be on a face, always inside a cell, even
    // after refinement.
    locationInMesh (500 42 42);


    // Whether any faceZones (as specified in the refinementSurfaces)
    // are only on the boundary of corresponding cellZones or also allow
    // free-standing zone faces. Not used if there are no faceZones.
    allowFreeStandingZoneFaces false;
}



// Settings for the snapping.
snapControls
{
    //- Number of patch smoothing iterations before finding correspondence
    //  to surface
    nSmoothPatch 10;

    //- Relative distance for points to be attracted by surface feature point
    //  or edge. True distance is this factor times local
    //  maximum edge length.
    tolerance 1.5;

    //- Number of mesh displacement relaxation iterations.
    nSolveIter 50;

    //- Maximum number of snapping relaxation iterations. Should stop
    //  before upon reaching a correct mesh.
    nRelaxIter 5;

    //- Highly experimental and wip: number of feature edge snapping
    //  iterations. Leave out altogether to disable.
    //  Of limited use in this case since faceZone faces not handled.
    //nFeatureSnapIter 15;

    // Feature snapping

        //- Number of feature edge snapping iterations.
        //  Leave out altogether to disable.
        nFeatureSnapIter 15;

        //- Detect (geometric only) features by sampling the surface
        //  (default=false).
        implicitFeatureSnap false;

        //- Use castellatedMeshControls::features (default = true)
        explicitFeatureSnap true;

        //- Detect points on multiple surfaces (only for explicitFeatureSnap)
        multiRegionFeatureSnap false;
}



// Settings for the layer addition.
addLayersControls
{
    relativeSizes false;

    // Per final patch (so not geometry!) the layer information
    layers
    {
        auto8
        {
            nSurfaceLayers 1;
        }
    }

    // Expansion factor for layer mesh
    expansionRatio 1.3;

    // Wanted thickness of final added cell layer. If multiple layers
    // is the thickness of the layer furthest away from the wall.
    // Relative to undistorted size of cell outside layer.
    finalLayerThickness 0.3036;

    // Minimum thickness of cell layer. If for any reason layer
    // cannot be above minThickness do not add layer.
    // Relative to undistorted size of cell outside layer.
    minThickness 0.005;

    // If points get not extruded do nGrow layers of connected faces that are
    // also not grown. This helps convergence of the layer addition process
    // close to features.
    // Note: changed(corrected) w.r.t 17x! (didn't do anything in 17x)
    nGrow 0;

    // Advanced settings

    // When not to extrude surface. 0 is flat surface, 90 is when two faces
    // are perpendicular
    featureAngle 30;

    // Maximum number of snapping relaxation iterations. Should stop
    // before upon reaching a correct mesh.
    nRelaxIter 3;

    // Number of smoothing iterations of surface normals
    nSmoothSurfaceNormals 1;

    // Number of smoothing iterations of interior mesh movement direction
    nSmoothNormals 3;

    // Smooth layer thickness over surface patches
    nSmoothThickness 2;

    // Stop layer growth on highly warped cells
    maxFaceThicknessRatio 0.5;

    // Reduce layer growth where ratio thickness to medial
    // distance is large
    maxThicknessToMedialRatio 1;

    // Angle used to pick up medial axis points
    // Note: changed(corrected) w.r.t 17x! 90 degrees corresponds to 130 in 17x.
    minMedianAxisAngle 90;

    // Create buffer region for new layer terminations
    nBufferCellsNoExtrude 0;

    // Overall max number of layer addition iterations. The mesher will exit
    // if it reaches this number of iterations; possibly with an illegal
    // mesh.
    nLayerIter 50;
}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
    //- Maximum non-orthogonality allowed. Set to 180 to disable.
    maxNonOrtho 65;

    //- Max skewness allowed. Set to <0 to disable.
    maxBoundarySkewness 20;
    maxInternalSkewness 4;

    //- Max concaveness allowed. Is angle (in degrees) below which concavity
    //  is allowed. 0 is straight face, <0 would be convex face.
    //  Set to 180 to disable.
    maxConcave 80;

    //- Minimum pyramid volume. Is absolute volume of cell pyramid.
    //  Set to very negative number (e.g. -1E30) to disable.
    minVol 0;

    //- Minimum quality of the tet formed by the face-centre
    //  and variable base point minimum decomposition triangles and
    //  the cell centre.  Set to very negative number (e.g. -1E30) to
    //  disable.
    //    <0 = inside out tet,
    //      0 = flat tet
    //      1 = regular tet
    minTetQuality 1e-30;

    //- Minimum face area. Set to <0 to disable.
    minArea -1;

    //- Minimum face twist. Set to <-1 to disable. dot product of face normal
    //- and face centre triangles normal
    minTwist 0.02;

    //- minimum normalised cell determinant
    //- 1 = hex, <= 0 = folded or flattened illegal cell
    minDeterminant 0.001;

    //- minFaceWeight (0 -> 0.5)
    minFaceWeight 0.02;

    //- minVolRatio (0 -> 1)
    minVolRatio 0.01;

    //must be >0 for Fluent compatibility
    minTriangleTwist -1;


    // Advanced

    //- Number of error distribution iterations
    nSmoothScale 4;
    //- amount to scale back displacement at error points
    errorReduction 0.75;
}


// Advanced

// Flags for optional output
// 0 : only write final meshes
// 1 : write intermediate meshes
// 2 : write volScalarField with cellLevel for postprocessing
// 4 : write current intersections as .obj files
debug 0;


// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1e-6;
I don't know what is wrong so if you have any idea how to fix it let me know.

Thanks!

David
Could you please upload the geometry... or a snapshot of it?

Haces April 15, 2013 10:54
2 Attachment(s)
Of course!! I forgot to attach the geometry.

Here you have the complete geometry and a detail.

Haces April 16, 2013 11:18
Hi,
It seems that I solved it. The problem was that the mesh was written in mm, so it was 1 km length. I was going to scale it after doing snappyHexMesh but It's better to do it before. It seems that the little displacements of the mesh was 1000 times bigger, and snappy tried to reduce this displacements.

jackeyhust May 21, 2013 11:37
Quote:
Originally Posted by Haces (Post 420981)
Hi,
It seems that I solved it. The problem was that the mesh was written in mm, so it was 1 km length. I was going to scale it after doing snappyHexMesh but It's better to do it before. It seems that the little displacements of the mesh was 1000 times bigger, and snappy tried to reduce this displacements.

Hi, friend,

I met the same problem as above. Could you explain it clearer? Thank you so much!Which should it be corrected?

Regards,

Jackie

Haces May 22, 2013 13:05
Hi jackeyhust,

In my case this error was mainly for three (four) reasons:

1. You didn't use the explicit feature to snap (check new releases of OF 2.2.0)
2. You have to play with the feature angle.
3. The snap did't work correctly because it used to give up. You should check your log file and observe the end of the morph iterations. If it's not working it will write 'giving up'. If you have this problem you have to relax the quality parameters and decrease the number of nFeatureSnapIter iterations.
EDIT: 4.Snappy doesn't like the blockMesh input. You should do the cells as hexagonal as possible. You can also play with the number of cells.

Hope this helps ;)

jackeyhust May 22, 2013 17:08
Quote:
Originally Posted by Haces (Post 429310)
Hi jackeyhust,

In my case this error was mainly for three (four) reasons:

1. You didn't use the explicit feature to snap (check new releases of OF 2.2.0)
2. You have to play with the feature angle.
3. The snap did't work correctly because it used to give up. You should check your log file and observe the end of the morph iterations. If it's not working it will write 'giving up'. If you have this problem you have to relax the quality parameters and decrease the number of nFeatureSnapIter iterations.
EDIT: 4.Snappy doesn't like the blockMesh input. You should do the cells as hexagonal as possible. You can also play with the number of cells.

Hope this helps ;)
Thanks, Haces,

it works now! But I still use explicit feature. I have read about the new features. But they said "The explicit method offers greater control and, from our experience, provides slightly better feature conformation. The implicit method has the advantage of being fully automated."

So what's your idea about this?

Thank you so much for the reply!

Jackie

kingmaker July 19, 2013 08:28
@Jackie
 
Hello Jackie

I am also having the problem that snappyHexMesh gives up with out finishing the snapping. It would be helpful how could you solve the problem.

I am meshing a centrifugal blower. I have a MRF included. as mentioned previously I checked/played some parameters like resolveFeatureAngle and all .. but could not get a good mesh. It completely misses the geometry... !!

Also in the log of snappy Hex mesh it says the given point is found in the cell -1 in region 0 of 4 ... !! Is that a problem... !!

chery1986 March 18, 2014 03:58
Hi, niklas. What is the trick to use snappyHexMesh? I have similar problem where snap doesn't work nicely. The problem is posted here http://www.cfd-online.com/Forums/ope...tml#post480610

Quote:
Originally Posted by niklas (Post 389430)
Does these work better?


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