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-   -   [snappyHexMesh] Unwanted mesh created by snappyHexMesh--baffle (https://www.cfd-online.com/Forums/openfoam-meshing/133872-unwanted-mesh-created-snappyhexmesh-baffle.html)

bieshuxuhe April 22, 2014 02:57

Unwanted mesh created by snappyHexMesh--baffle
 
2 Attachment(s)
hi !
I am new to snappyHexMesh ! I use openfoam-2.2.2 ! The picture one is what I want , but the picture two is what I get .
could you help me what is wrong ?

the blockMeshDict is
Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                |                                                |
| \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox          |
|  \\    /  O peration    | Version:  2.2.2                                |
|  \\  /    A nd          | Web:      www.OpenFOAM.org                      |
|    \\/    M anipulation  |                                                |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version    2.0;
    format      ascii;
    class      dictionary;
    object      blockMeshDict;
}
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 convertToMeters 0.01;
 vertices
(
    (0 0 0)
    (10 0 0)
    (10 10 0)
    (0 10 0)
    (0 0 5)
    (10 0 5)
    (10 10 5)
    (0 10 5)
   
);
 blocks
(
    hex (0 1 2 3 4 5 6 7) (20 20 10) simpleGrading (1 1 1)
);
 edges
(
);
 boundary
(
    bottom
    {
        type patch;
        faces
        (
            (1 5 4 0)
        );
    }
    top
    {
        type patch ;
        faces
        (
            (3 7 6 2)
        );
    }
    left
    {
        type patch;
        faces
        (
            (0 4 7 3)
        );
    }
    right
    {
        type patch;
        faces
        (
            (2 6 5 1)
        );
    }
    front
    {
        type wall;
        faces
        (
            (4 5 6 7)
        );
    }
    back
    {
        type wall;
        faces
        (
            (0 3 2 1)
        );
    }
);
 // ************************************************************************* //

the snappyHexMeshDict is
Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                |                                                |
| \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox          |
|  \\    /  O peration    | Version:  2.2.2                                |
|  \\  /    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      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
{
    baffle
    {
        type searchablePlate;
        origin (0.05 -0.01 -0.01);
        span (0 0.06 0.11);
        regions
        {
            region0
            {
              name  baffle;
            }
        }
    }
};
 
 // 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 100000;
    // 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 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)
    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
    (
        //{
        //    file "someLine.eMesh";
        //    levels ((0.1 2));
        //}
    );
 
    // 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
    {
        baffle
        {
            level (1 2);
        }
    }
    // Resolve sharp angles
    resolveFeatureAngle 30;
 
    // 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
    {
    }
 
    // 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 (5.1 5.1 2.5);
    locationInMesh (0.001 0.001 0.005);
   
    // 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
    {
        cylinder_region0
        {
            nSurfaceLayers 3;
        }
    }
    // Expansion factor for layer mesh
    expansionRatio 1.2;
    //- 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 0.6;
    //- 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 220;
    //- 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;
 
// ************************************************************************* //

And Allrun is
Code:

#!/bin/sh
cd ${0%/*} || exit 1    # run from this directory
 
# Source tutorial run functions
. $WM_PROJECT_DIR/bin/tools/RunFunctions
runApplication foamCleanTutorials
runApplication blockMesh 2>&1
runApplication snappyHexMesh -overwrite 2>&1
#runApplication icoFoam


bieshuxuhe April 22, 2014 22:00

someone told me I did right ! it is problem of display in paraView !:)
do you know how to make it looks like the picture two ?
thanks !

bieshuxuhe April 23, 2014 01:59

Don't select internalMesh ,select patch( front e.g.) ! then you will see the picture one !
if you select internalMesh , you will see the picture two !


with best wishes


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