snappyHexMeshDict

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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


// 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
{
  GEOM_backFastback.stl
    { type triSurfaceMesh; }
  GEOM_belt.stl
    { type triSurfaceMesh; }
  GEOM_bodySmooth.stl
    { type triSurfaceMesh; }
  GEOM_curvedPipe.stl
    { type triSurfaceMesh; }
  GEOM_frontWheelarm.stl
    { type triSurfaceMesh; }
  GEOM_frontWheel.stl
    { type triSurfaceMesh; }
  GEOM_midPipe.stl
    { type triSurfaceMesh; }
  GEOM_mirrors.stl
    { type triSurfaceMesh; }
  GEOM_mountingRadiator.stl
    { type triSurfaceMesh; }
  GEOM_rearWheelarm.stl
    { type triSurfaceMesh; }
  GEOM_rearWheel.stl
    { type triSurfaceMesh; }
  GEOM_scoopFlap6deg.stl
    { type triSurfaceMesh; }
  GEOM_splitter.stl
    { type triSurfaceMesh; }
  GEOM_windTunnel.stl
    { type triSurfaceMesh; }

  REF_03.stl
    { type triSurfaceMesh; }
  REF_04.stl
    { type triSurfaceMesh; }
  REF_05.stl
    { type triSurfaceMesh; }
  REF_06.stl
    { type triSurfaceMesh; }
  REF_07.stl
    { type triSurfaceMesh; }
};



// 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 10000000;

  // 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 200000000;

  // 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 10;

  // 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 0.10;


  // 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 ();


  // 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
    {
      GEOM_windTunnel.stl
        { level (5 6); }
      "GEOM.*"
        { level (7 8); }
    }

  // Resolve sharp angles
  resolveFeatureAngle 140;


  // 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
    {
      REF_03.stl
        {
          mode inside;
          levels ((0 2));
        }
      REF_04.stl
        {
          mode inside;
          levels ((0 3));
        }
      REF_05.stl
        {
          mode inside;
          levels ((0 4));
        }
      REF_06.stl
        {
          mode inside;
          levels ((0 5));
        }
      REF_07.stl
        {
          mode inside;
          levels ((0 6));
        }
    }


  // 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 (-900 0 200);


  // 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 true;
}



// Settings for the snapping.
snapControls
{
  //- Number of patch smoothing iterations before finding correspondence
  //  to surface
  nSmoothPatch 3;

  //- Relative distance for points to be attracted by surface feature point
  //  or edge. True distance is this factor times local
  //  maximum edge length.
  tolerance 4.0;

  //- Number of mesh displacement relaxation iterations.
  nSolveIter 0;

  //- 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.
  //  Do not use here since mesh resolution too low and baffles present
  nFeatureSnapIter 10;
}



// Settings for the layer addition.
addLayersControls
{
    // Are the thickness parameters below relative to the undistorted
    // size of the refined cell outside layer (true) or absolute sizes (false).
    relativeSizes true;

    // Per final patch (so not geometry!) the layer information
    layers
    {
        ".*"
        {
            nSurfaceLayers 5;
        }
    }

    // Expansion factor for layer mesh
    expansionRatio 1.4;

    //- 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.
    //  is the thickness of the layer furthest away from the wall.
    //  See relativeSizes parameter.
    finalLayerThickness 1;

    //- 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 0.1;

    //- 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
    //  make straight angle.
    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 10;

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

    // Reduce layer growth where ratio thickness to medial
    // distance is large
    maxThicknessToMedialRatio 0.3;

    // 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 a sensible fraction of the smallest cell volume expected.
    //  Set to very negative number (e.g. -1E30) to disable.
    minVol 1e-13;

    //- Minimum quality of the tet formed by the face-centre
    //  and variable base point minimum decomposition triangles and
    //  the cell centre. This has to be a positive number for tracking
    //  to work. 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;


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