openfoam/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMeshDict

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.0                                   |
|   \\  /    A nd           | Web:      http://www.openfoam.org               |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/

FoamFile
{
    version         2.0;
    format          ascii;

    root            "/home/penfold/mattijs/foam/mattijs2.1/run/icoFoam";
    case            "cavity";
    instance        "system";
    local           "";

    class           dictionary;
    object          autoHexMeshDict;
}

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

// Which phases to run.
doRefine true;
doSnap   true;
doLayers true; // includes autoMergeFaces


// Whether to dump intermediate meshes and print lots
// 1 : write mesh
// 2 : write volScalarField with cellLevel for postprocessing
// 4 : write current intersections as .obj files
debug 0;

refineDict
{
    // Which part to keep.
    // NOTE: This point should never be on a face, always inside a cell, even
    // after refinement.
    keepPoints ((3 0.28 0.43));

    // Whether to remove/split cells likely to give problems when snapping
    handleSnapProblems on;

    // Merge tolerance. Is fraction of overall bounding box of initial mesh
    mergeTolerance 1E-6;

    // While refining maximum number of cells per processor. This is basically
    // the number of cells that fit on a processor. If you choose this too small
    // it will do just more refinement iterations to obtain a similar mesh.
    procCellLimit 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.
    cellLimit 2000000;


    // 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)
    minimumRefine 0;




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


    // Feature Edge Refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~

    // External feature file. Read from constant/triSurface for now.
    // Limitations:
    // - either start or edge of any feature line has to be inside domain
    //   and be visible from keepPoint on starting mesh.
    // - refining cells containing features is separate phase before refining
    //   based on surface.
    // - no load balancing, no check for cellLimit is done while doing this.
    features
    (
    //    {
    //        file "someLine.eMesh";
    //        level 2;
    //    }
    );


    // Internal Mesh Refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~

    // Specifies the areas where the refinement has to be a certain level.
    // These surfaces have to be closed. Refinement is either inside
    // (refineInside = true) or outside. (note:insideness or outsideness
    // is with respect to far away)
    // Note:that even using these the transition can never be faster than
    // nBufferLayers!
    // Note:the refinement level can never be higher than any of the surfaces
    // they overlap with. See below for the surface refinement level specification.
    refinementShells
    (
        {
            //type triSurfaceMesh;
            //name cube1x1x1.stl;
            type searchableBox;
            name box1x1x1;
            min (2.5 -0.5 -0.5);
            max (3.5 0.5 0.5);

            level 4;
            refineInside true;
        }
    );


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

    // Curvature. Cosine of angle between two neighbouring surface intersections.
    // Only used if cell level > minLevel and < maxLevel.
    curvature 0.5;


    // Overall the refinement is according to the following rules:
    // - if the cell-cell vector intersects a surface any cell that
    //   is less refined than the minRefinementLevel of the surface gets refined.
    // - else if the refinement level of the cell is between the
    //   minRefinementLevel and maxRefinementLevel the cell gets refined if
    //      - the normal of neighbouring surface intersections differ by more
    //        than above curvature
    //      - or if neighbouring surface intersections are on different surfaces or
    //        different surface regions.


    // surfaces
    surfaces
    (
        {
            name    sphere;
            file    "sphere.stl";

            // Surface wide refinement level
            minRefinementLevel 1;
            maxRefinementLevel 1;

            // Layers
            surfaceLayers 1;

            // Region specific refinement level
            regions
            (
                {
                    name firstSolid;
                    minRefinementLevel 3;
                    maxRefinementLevel 3;
                    surfaceLayers 2;
                }
                {
                    name secondSolid;
                    minRefinementLevel 1;
                    maxRefinementLevel 1;
                    surfaceLayers 1;
                }
            );
        }
    );
}

// For snapping
snapDict
{
    //- 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.
    snapTol 4.0;

    //- Whether to move internal mesh as well as boundary
    smoothMesh true;

    //- Number of mesh displacement smoothing iterations.
    nSmoothDispl 30;

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


// For cell layers
layerDict
{
    //- When not to extrude surface. 0 is flat surface, 90 is when two faces
    //  make straight angle.
    featureAngle 60;

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


    //- Minimum thickness of cell layer. If for any reason layer cannot be
    //  above minThickness do not add layer if thickness below minThickNess.
    //  Relative to undistorted cell size
    minThickness 0.25;

    //- If points get not extruded do nGrow layers of connected faces that are
    //  not grown. Is used to not do layers at all close to features.
    nGrow 1;

    // Expansion factor for layer mesh
    expansionRatio 1.3;	

    // Ratio of cell size in final added cell layer to cell size 
    // outside layer 
    finalLayerRatio 0.3;

    // 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
    minMedianAxisAngle 130;

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

    thickness 0.5;
    nSmoothDispl 4;
}


// For mesh motion
motionDict
{
    //
    // Mesh Quality Parameters. Decide when mesh is good enough to stop
    // smoothing.
    //

    //- 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 projected area v.s. actual area. Set to -1 to disable.
    minFlatness 0.5;

    //- Minimum pyramid volume. Is absolute volume of cell pyramid.
    //  Set to very negative number (e.g. -1E30) to disable.
    minVol 1e-13;

    //- 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 0.05;

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

    //- minFaceWeight (0 -> 0.5) 
    minFaceWeight 0.05;

    //- 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;
}


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