[JD_PM]

Hi there!

I am trying to set up an axisymmetric mesh of my original case (pipe+orifice) to save computational cost and time.

I managed to set up the mesh but once I try to run interPhaseChangeFoam the simulation crashes (it does not even start).

The problem is the mesh, given that checkMesh yields the following

checkMesh

Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           3162
    internal points:  0
    faces:            5840
    internal faces:   2784
    cells:            1431
    faces per cell:   6.02655
    boundary patches: 5
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     1265
    prisms:        61
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     105
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            6   9
            7   93
            8   3

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
                   inlet       12       25  ok (non-closed singly connected)
                  outlet       12       25  ok (non-closed singly connected)
               symmetry1     1431     1615  ok (non-closed singly connected)
               symmetry2     1431     1615  ok (non-closed singly connected)
                 orifice      170      342  ok (non-closed singly connected)

Checking geometry...
    Overall domain bounding box (-0.0615 0 -0.000327145) (0.1785 0.00749286 0.000327145)
    Mesh has 2 geometric (non-empty/wedge) directions (1 1 0)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Wedge symmetry1 with angle 2.5 degrees
    Wedge symmetry2 with angle 2.5 degrees
    All edges aligned with or perpendicular to non-empty directions.
    Boundary openness (-2.98248e-19 3.25799e-16 -2.20362e-16) OK.
    Max cell openness = 2.77951e-16 OK.
    Max aspect ratio = 8.88747 OK.
    Minimum face area = 1.66976e-10. Maximum face area = 4.13566e-06.  Face area magnitudes OK.
 ***Zero or negative cell volume detected.  Minimum negative volume: -9.17165e-10, Number of negative volume cells: 1431
  <<Writing 1431 zero volume cells to set zeroVolumeCells
    Mesh non-orthogonality Max: 180 average: 168.009
 ***Number of non-orthogonality errors: 2784.
  <<Writing 2784 non-orthogonal faces to set nonOrthoFaces
 ***Error in face pyramids: 8624 faces are incorrectly oriented.
  <<Writing 5840 faces with incorrect orientation to set wrongOrientedFaces
 ***Max skewness = 90.0887, 2 highly skew faces detected which may impair the quality of the results
  <<Writing 2 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 4 mesh checks.

End

Could someone please suggest what could be the problem?

I attach more relevant files below. Please let me know if more information is required.

Thanks in advance!

blockMesh

convertToMeters 1000;

vertices        
(
    (-0.0615 0 0)
    (0.1785 0 0)
    (0.1785  0.01 0)
    (-0.0615  0.01 0)
    (-0.0615  0 0.01)
    (0.1785 0 0.01)
    (0.1785  0.01 0.01)
    (-0.0615  0.01 0.01)
);

blocks          
(
    hex (0 1 2 3 4 5 6 7) (180 24 24) simpleGrading (1 1 1)
);

edges           
(
);

patches //clockwise (does this actually matter?)       
(
    patch walls
    (
        (3 7 6 2) //upper
        (4 5 6 7) //side-left wall
     )
    patch inlet
    (
        (0 4 7 3)
    )
    patch outlet
    (
        (2 6 5 1)
    )
   	symmetry symmetry1
    (
		(0 3 2 1) //side-right wall
    )
	symmetry symmetry2
	(
		(1 5 4 0) //lower-wall	
	)
);

mergePatchPairs 
(
);

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

snappyHexMeshDict

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
{

    orifice
    {
        type triSurfaceMesh;
        file "orifice.stl";
    }

    inlet
    {
        type triSurfaceMesh;
        file "inlet.stl";
    }
    outlet
    {
        type triSurfaceMesh;
        file "outlet.stl";
    }
    wall
    {
        type triSurfaceMesh;
        file "wall.stl";
    }
    refinementBox
    {
        type searchableBox;
        min (-10 -8 -8);
        max (20 8 8);
    }
    EnclosingRefinementBox
    {
        type searchableBox;
        min (-20 -8 -8);//min (-60 -8 -8);
        max (40 8 8);//max (120 8 8);
    }
};

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 8;  // 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 "orifice.eMesh"; level 3;}
        {file "wall.eMesh"; level 1;}


    );

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

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

	orifice  {level (3 3);}
	wall  {level (1 1);}



    }


    resolveFeatureAngle 5;  // Resolve sharp angles // Default 30
    refinementRegions        // In descending levels of fine-ness
    {

      refinementBox
      {
            mode inside;
            levels ((1E15 3));
      }
      EnclosingRefinementBox
      {
            mode inside;
            levels ((1E15 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
    {
        orifice
        {
            nSurfaceLayers          8;
            expansionRatio          1.1;
            finalLayerThickness     0.01;
            minThickness            0.001;
        }

        wall
        {
            nSurfaceLayers          8;
            expansionRatio          1.1;
            finalLayerThickness     0.1;
            minThickness            0.01;
        }

    }

    expansionRatio 1.2;
    finalLayerThickness 1.0; //was 0.00016
    minThickness 0.05; //was 0.00008
    nGrow 1; // 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 25; // 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 -1;
    minArea -1;
    minTwist 0.02;
    minDeterminant 0.001;
    minFaceWeight 0.02;
    minVolRatio 0.01;
    minTriangleTwist -1;

    // Advanced

    nSmoothScale 4;
    errorReduction 0.75;
}

// Advanced

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;

extrudeMeshDict

constructFrom patch;
sourceCase "$FOAM_CASE";

sourcePatches (symmetry1);
exposedPatchName symmetry2;

extrudeModel        wedge;

sectorCoeffs
{
    axisPt          (0 0 0);
    axis            (1 0 0);
    angle           5;
}

flipNormals false;
mergeFaces false;

[Tobermory]

Your first problem is:

 ***Zero or negative cell volume detected.  Minimum negative volume: -9.17165e-10, Number of negative volume cells: 1431
  <<Writing 1431 zero volume cells to set zeroVolumeCells

All of your cells are inside out (negative volume) - that's a no no. In extrudeMeshDict, try change

    axis            (1 0 0);

to

    axis            (-1 0 0);

and redo the extrusion. That should fix the first (and hopefully only) problem. If checkmesh still complains, then you'll need to sort out the other errors before trying to run. Good luck!

[JD_PM]

Thank you very much! The mesh is not perfect but now the simulation runs!

Checking geometry...
    Overall domain bounding box (-0.0615 0 -6.8029e-10) (0.1785 0.0075 0.000653668)
    Mesh has 2 geometric (non-empty/wedge) directions (1 1 0)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Wedge symmetry1 with angle 4.08921e-05 degrees
    Wedge symmetry2 with angle 5 degrees
 ***Number of edges not aligned with or perpendicular to non-empty directions: 1547
  <<Writing 3094 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (1.70427e-19 -1.91051e-17 -2.88085e-15) OK.
    Max cell openness = 2.2228e-16 OK.
    Max aspect ratio = 8.87889 OK.
    Minimum face area = 1.66977e-10. Maximum face area = 4.13566e-06.  Face area magnitudes OK.
    Min volume = 1.7067e-12. Max volume = 9.17161e-10.  Total volume = 5.81139e-07.  Cell volumes OK.
    Mesh non-orthogonality Max: 60.7899 average: 11.9914
    Non-orthogonality check OK.
    Face pyramids OK.
 ***Max skewness = 90.1051, 2 highly skew faces detected which may impair the quality of the results
  <<Writing 2 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 2 mesh checks.

End