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Does extrude and createPatch utilities degrade mesh quality?

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Old   February 11, 2019, 10:04
Default Does extrude and createPatch utilities degrade mesh quality?
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Hi guys,

Im relatively new to the OpenFoam, and my question is as mentioned above.


The point of this project is to project a 3d chemical reactor to a 2d dimension.



The problem is, the snappyHexMesh works just fine, the checkMesh report is as shown below:




Checking geometry...
Overall domain bounding box (-0.02026639 -0.4499996 -0.3381794) (0.02 2.914998 20.32082)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (-4.47195e-15 -1.377571e-16 -1.32104e-18) OK.
Max cell openness = 7.084912e-16 OK.
Max aspect ratio = 67.56328 OK.
Minimum face area = 4.65e-10. Maximum face area = 0.002978817. Face area magnitudes OK.
Min volume = 9.507243e-10. Max volume = 0.0001199761. Total volume = 0.8087285. Cell volumes OK.
Mesh non-orthogonality Max: 65.00413 average: 12.09625
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 3.908088 OK.
Coupled point location match (average 0) OK.

Mesh OK.







But as I was trying to extrude the relatively thin Mesh to a paper thin(one cell layer)
The mesh got degraded and the report went wrong





***Zero or negative face area detected. Minimum area: 0
<<Writing 8 zero area faces to set zeroAreaFaces
Min volume = 4.4325e-10. Max volume = 0.0001489268. Total volume = 0.9998755. Cell volumes OK.
Mesh non-orthogonality Max: 85.722 average: 8.44269
*Number of severely non-orthogonal (> 70 degrees) faces: 45.
Non-orthogonality check OK.
<<Writing 45 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 1 faces are incorrectly oriented.
<<Writing 1 faces with incorrect orientation to set wrongOrientedFaces
***Max skewness = 5.384117e+151, 53 highly skew faces detected which may impair the quality of the results
<<Writing 53 skew faces to set skewFaces
Coupled point location match (average 0) OK.

Failed 3 mesh checks.


Can somebody be so kind and help me with it? If not the specific solutions, telling me where the errors would be is also very appreciated!


Im stucked here for more than one week, tried everything but just cant figure it out.

Thank you guys so much!



I would attach the Dict files below.
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Old   February 11, 2019, 15:25
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Could you please update your case file?

Quote:
Originally Posted by Sashihara View Post
Hi guys,

Im relatively new to the OpenFoam, and my question is as mentioned above.


The point of this project is to project a 3d chemical reactor to a 2d dimension.



The problem is, the snappyHexMesh works just fine, the checkMesh report is as shown below:




Checking geometry...
Overall domain bounding box (-0.02026639 -0.4499996 -0.3381794) (0.02 2.914998 20.32082)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (-4.47195e-15 -1.377571e-16 -1.32104e-18) OK.
Max cell openness = 7.084912e-16 OK.
Max aspect ratio = 67.56328 OK.
Minimum face area = 4.65e-10. Maximum face area = 0.002978817. Face area magnitudes OK.
Min volume = 9.507243e-10. Max volume = 0.0001199761. Total volume = 0.8087285. Cell volumes OK.
Mesh non-orthogonality Max: 65.00413 average: 12.09625
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 3.908088 OK.
Coupled point location match (average 0) OK.

Mesh OK.







But as I was trying to extrude the relatively thin Mesh to a paper thin(one cell layer)
The mesh got degraded and the report went wrong





***Zero or negative face area detected. Minimum area: 0
<<Writing 8 zero area faces to set zeroAreaFaces
Min volume = 4.4325e-10. Max volume = 0.0001489268. Total volume = 0.9998755. Cell volumes OK.
Mesh non-orthogonality Max: 85.722 average: 8.44269
*Number of severely non-orthogonal (> 70 degrees) faces: 45.
Non-orthogonality check OK.
<<Writing 45 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 1 faces are incorrectly oriented.
<<Writing 1 faces with incorrect orientation to set wrongOrientedFaces
***Max skewness = 5.384117e+151, 53 highly skew faces detected which may impair the quality of the results
<<Writing 53 skew faces to set skewFaces
Coupled point location match (average 0) OK.

Failed 3 mesh checks.


Can somebody be so kind and help me with it? If not the specific solutions, telling me where the errors would be is also very appreciated!


Im stucked here for more than one week, tried everything but just cant figure it out.

Thank you guys so much!



I would attach the Dict files below.
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Ran
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Old   February 11, 2019, 15:59
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HI
I'm not sure if I have posted it, its my first time being here
Attached Files
File Type: txt blockMesh.txt (1,012 Bytes, 2 views)
File Type: txt createPatchDict.txt (1.0 KB, 3 views)
File Type: txt extrudeMeshDict.txt (1.3 KB, 6 views)
File Type: txt snappyHexMesh.txt (4.5 KB, 2 views)
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Old   February 11, 2019, 16:01
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Quote:
Originally Posted by random_ran View Post
Could you please update your case file?
Hi ran, I have posted the codes down below, can u take a quick look thx.

Best regards
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Old   February 11, 2019, 16:08
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I think I just figured out how to post it in between the text.
For the convenience

blockMeshDict
Code:
convertToMeters 1; // does nothing in this case, 0.1 would shrink it by 10x

vertices   // (x y z)   
(
    (-0.1 -1 -1)       // was 0 0 0
    (0.1 -1 -1)     // was 0.2 0 0
    (0.1 4 -1)   // was 0.2 0.2 0
    (-0.1 4 -1)     // was 0 0.2 0 
    (-0.1 -1 23)     // was 0 0 0.2
    (0.1 -1 23)   // was 0.2 0 0.2
    (0.1 4 23) // was 0.2 0.2 0.2
    (-0.1 4 23)   // was 0 0.2 0.2
);

blocks          
(
    hex (0 1 2 3 4 5 6 7) (100 100 100) simpleGrading (1 1 1)
);

edges           
(
);

patches         //copied from DICAT shm example "M3_mixing elbow1"
(               
    patch maxY 
    (
        (3 7 6 2)
    )
    patch minX
    (
        (0 4 7 3)
    )
    patch maxX
    (
        (2 6 5 1)
    )
    patch minY
    (
        (1 5 4 0)
    )
    patch minZ
    (
        (0 3 2 1)
    )
    patch maxZ
    (
        (4 5 6 7)
    )
);

mergePatchPairs
(
);

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

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

// Which of the steps to run
castellatedMesh true;    // make basic mesh ?
snap            true;    // decide to snap back to surface ?
addLayers       true;   // decide to add viscous layers ?


geometry // Load in STL files here
{

coldWalls.stl {type triSurfaceMesh; name coldWalls;}
hotWalls.stl {type triSurfaceMesh; name hotWalls;}
resevoir.stl {type triSurfaceMesh; name resevoir;}
rohrOben.stl {type triSurfaceMesh; name rohrOben;}
rohrUnten.stl {type triSurfaceMesh; name rohrUnten;}
volume.stl {type triSurfaceMesh; name volume;}
refinementBox {type searchableBox; min (-0.1 -0.1 -0.05); max ( 0.1 0.1 0.05);}
};

castellatedMeshControls
{
    maxLocalCells 1000000;  //max cells per CPU core
    maxGlobalCells 2000000; //max cells to use before mesh deletion step
    minRefinementCells 10;  //was 0 - zero means no bad cells are allowed during refinement stages
    maxLoadUnbalance 0.10;
    nCellsBetweenLevels 1;  // expansion factor between each high & low refinement zone

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

    features // taken from STL from each .eMesh file created by "SurfaceFeatureExtract" command
    (
        {file "resevoir.eMesh"; level 2;} 
        {file "coldWalls.eMesh"; level 2;}
        {file "hotWalls.eMesh"; level 2;}
        {file "rohrOben.eMesh"; level 2;} 
        {file "rohrUnten.eMesh"; level 2;} 
    );

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

    refinementSurfaces // Surface-wise min and max refinement level
    {

coldWalls {level (2 2);} 
hotWalls {level (2 2);} // was 4 4
resevoir {level (2 2);} // was 4 4
rohrOben {level (2 2);} // was 4 4
rohrUnten {level (2 2);} // was 4 4
    }  


    resolveFeatureAngle 80;  // Resolve sharp angles // Default 30
    refinementRegions        // In descending levels of fine-ness
    {volume {mode distance; levels ((0.0006 4) (0.002 3) (0.01 2));}} // was ((0.001 4) (0.003 3) (0.01 2))
    locationInMesh (0 0 0);  //to decide which side of mesh to keep **
    allowFreeStandingZoneFaces true;
}


// Settings for the snapping.
snapControls
{
    nSmoothPatch 3;
    tolerance 4.0;
    nSolveIter 30;
    nRelaxIter 5;
    nFeatureSnapIter 15; // default is 10
    
// New settings from openfoam 2.2 onwards for SHMesh

implicitFeatureSnap false; // default is false - detects without doing surfaceFeatureExtract
explicitFeatureSnap true; // default is true
multiRegionFeatureSnap false; // deafault is false - detects features between multiple surfaces

}



// Settings for the layer addition.
addLayersControls //add the PATCH names from inside the STL file so STLpatchName_insideSTLName 
{
    relativeSizes false; // was true
    layers
    {
coldWalls
          {nSurfaceLayers 2;} // was 3
hotWalls 
 {nSurfaceLayers 2;} // was 3
resevoir
 {nSurfaceLayers 2;} // was 3
rohrOben
 {nSurfaceLayers 2;} // was 3
    rohrUnten
 {nSurfaceLayers 2;} // was 3
   }

    expansionRatio 1.3;
    finalLayerThickness 0.00016; //was 0.00016
    minThickness 0.00008; //was 0.00008
    nGrow 0; // was 1 


    // Advanced settings

    featureAngle 80; // was 70 //- When not to extrude surface. 0 is flat, 90 is right angle.
    nRelaxIter 3;  //- Max# of snapping relaxation iter. Should stop before upon reaching a correct mesh.
    nSmoothSurfaceNormals 1;  // Number of smoothing iterations of surface normals
    nSmoothNormals 3; // Number of smoothing iterations of interior mesh movement direction
    nSmoothThickness 10;  // Smooth layer thickness over surface patches
    maxFaceThicknessRatio 0.5; // Stop layer growth on highly warped cells
    maxThicknessToMedialRatio 0.3; // Reduce layer growth where ratio thickness to medial distance is large
    minMedianAxisAngle 130;  // Angle used to pick up medial axis points
    nBufferCellsNoExtrude 0;   // Create buffer region for new layer terminations
    nLayerIter 50; // Overall max number of layer addition iterations
}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
    maxNonOrtho 65;
    maxBoundarySkewness 20;
    maxInternalSkewness 4;
    maxConcave 80;
    minFlatness 0.5;
    minVol 1e-13;
    minTetQuality 1e-9;
    minArea -1;
    minTwist 0.02;
    minDeterminant 0.001;
    minFaceWeight 0.02;
extrudeMeshDict
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      extrudeMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// What to extrude:
//      patch   : from patch of another case ('sourceCase')
//      mesh    : as above but with original case included
//      surface : from externally read surface

constructFrom patch;
sourceCase "../mammutSnappy";
sourcePatches (maxX);

// If construct from patch: patch to use for back (can be same as sourcePatch)
exposedPatchName minX;

// Flip surface normals before usage. Valid only for extrude from surface or
// patch.
flipNormals false;

//- Linear extrusion in point-normal direction
extrudeModel        linearNormal;

nLayers             1;


expansionRatio      1.0;

linearNormalCoeffs
{
    thickness       0.05;
}

linearDirectionCoeffs
{
    direction       (0 1 0);
    thickness       0.005;
}

sectorCoeffs
{
axisPt (0 0 0);
axis (0 1 0);
angle 1.000000;
}

// Do front and back need to be merged? Usually only makes sense for 360
// degree wedges.
mergeFaces false;   // true;

// Merge small edges. Fraction of bounding box.
mergeTol 0;


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
createPatchDict
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      createPatchDict;
}

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

pointSync false;

patches
(
    {
        // Name of new patch
        name front;

        // Type of new patch
        patchInfo
        {
            type empty;
        }

        // How to construct: either from 'patches' or 'set'
        constructFrom patches;

        // If constructFrom = patches : names of patches. Wildcards allowed.
        patches (maxX);
    }
    {
        // Name of new patch
        name back;

        // Type of new patch
        patchInfo
        {
            type empty;
        }

        // How to construct: either from 'patches' or 'set'
        constructFrom patches;

        // If constructFrom = patches : names of patches. Wildcards allowed.
        patches (minX);
    }
);

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

Thanks again for your patience and help
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