OpenFOAMの熱流体固体連成のチュートリアル（snappyMultiRegionHeater）

surfaceFeatureExtract

続いてsltファイルを元に特徴線を作成します。
これは次のsnappyHexMeshで使用されます。

system/surfaceFeatureExtractDict

geom.stl
{
    extractionMethod    extractFromSurface;

    // Mark edges whose adjacent surface normals are at an angle less
    // than includedAngle as features
    // - 0  : selects no edges
    // - 180: selects all edges
    includedAngle       150;

    // Write options
    writeFeatureEdgeMesh    yes;

    // Write features to obj format for postprocessing
    writeObj                yes;
}

geom.stl

{

extractionMethod extractFromSurface;

// Mark edges whose adjacent surface normals are at an angle less

// than includedAngle as features

// - 0 : selects no edges

// - 180: selects all edges

includedAngle 150;

// Write options

writeFeatureEdgeMesh yes;

// Write features to obj format for postprocessing

writeObj yes;

}

snappyHexMesh

続いてstlファイルを元に形状に沿ってメッシュ作成します。
snappyHexMeshの中身は長いですが全部書いておきます。

system/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
{
    geom.stl
    {
        type triSurfaceMesh;
        name geom;
    }
}


// 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;

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



    // 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 "geom.extendedFeatureEdgeMesh";    //"geom.eMesh";
            level 1;
        }
    );



    // 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
        {
            // Surface-wise min and max refinement level
            level (1 1);
        }
    }

    // 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
    {
        //refinementBox
        //{
        //    mode inside;
        //    levels ((1E15 4));
        //}
    }


    // 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.
    locationsInMesh
    (
        (( 0.005 0.005  0.005) heater)
        (( 0.05  0.005  0.005) rightSolid)
        ((-0.05  0.005  0.005) leftSolid)
        ((-0.05  0.015  0.005) topAir)
        ((-0.05 -0.015  0.005) bottomAir)
    );


    // 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 false;
}



// 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 1.0;

    //- Number of mesh displacement relaxation iterations.
    nSolveIter 30;

    //- 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.
    //  Of limited use in this case since faceZone faces not handled.
    nFeatureSnapIter 10;
}



// Settings for the layer addition.
addLayersControls
{
    relativeSizes true;

    // Per final patch (so not geometry!) the layer information
    layers
    {
        maxY
        {
            nSurfaceLayers 3;
        }
    }

    // Expansion factor for layer mesh
    expansionRatio 1.3;

    // 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.
    // 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 1.7.x! (didn't do anything in 1.7.x)
    nGrow 0;

    // Advanced settings

    // When not to extrude surface. 0 is flat surface, 90 is when two faces
    // are perpendicular
    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 2;

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

    // Reduce layer growth where ratio thickness to medial
    // distance is large
    maxThicknessToMedialRatio 1;

    // Angle used to pick up medial axis points
    // Note: changed(corrected) w.r.t 1.7.x! 90 degrees corresponds to 130
    // in 1.7.x.
    minMedialAxisAngle 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
{
    #include "meshQualityDict"

    // Advanced

    //- Number of error distribution iterations
    nSmoothScale 4;
    //- Amount to scale back displacement at error points
    errorReduction 0.75;
}


// Advanced

// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1e-6;

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// 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

{

geom.stl

{

type triSurfaceMesh;

name geom;

}

// 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;

// Number of buffer layers between different levels.

// 1 means normal 2:1 refinement restriction, larger means slower

// refinement.

nCellsBetweenLevels 2;

// 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 "geom.extendedFeatureEdgeMesh"; //"geom.eMesh";

level 1;

}

);

// 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

{

// Surface-wise min and max refinement level

level (1 1);

}

// 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

{

//refinementBox

//{

// mode inside;

// levels ((1E15 4));

//}

}

// 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.

locationsInMesh

(

(( 0.005 0.005 0.005) heater)

(( 0.05 0.005 0.005) rightSolid)

((-0.05 0.005 0.005) leftSolid)

((-0.05 0.015 0.005) topAir)

((-0.05 -0.015 0.005) bottomAir)

);

// 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 false;

}

// 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 1.0;

//- Number of mesh displacement relaxation iterations.

nSolveIter 30;

//- 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.

// Of limited use in this case since faceZone faces not handled.

nFeatureSnapIter 10;

}

// Settings for the layer addition.

addLayersControls

{

relativeSizes true;

// Per final patch (so not geometry!) the layer information

layers

{

maxY

{

nSurfaceLayers 3;

}

// Expansion factor for layer mesh

expansionRatio 1.3;

// 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.

// 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 1.7.x! (didn't do anything in 1.7.x)

nGrow 0;

// Advanced settings

// When not to extrude surface. 0 is flat surface, 90 is when two faces

// are perpendicular

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 2;

// Stop layer growth on highly warped cells

maxFaceThicknessRatio 0.5;

// Reduce layer growth where ratio thickness to medial

// distance is large

maxThicknessToMedialRatio 1;

// Angle used to pick up medial axis points

// Note: changed(corrected) w.r.t 1.7.x! 90 degrees corresponds to 130

// in 1.7.x.

minMedialAxisAngle 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

{

#include "meshQualityDict"

// Advanced

//- Number of error distribution iterations

nSmoothScale 4;

//- Amount to scale back displacement at error points

errorReduction 0.75;

}

// Advanced

// Merge tolerance. Is fraction of overall bounding box of initial mesh.

// Note: the write tolerance needs to be higher than this.

mergeTolerance 1e-6;

大事なのはcastellatedMeshControlsの{}の中の以下の部分です。

    locationsInMesh
    (
        (( 0.005 0.005  0.005) heater)
        (( 0.05  0.005  0.005) rightSolid)
        ((-0.05  0.005  0.005) leftSolid)
        ((-0.05  0.015  0.005) topAir)
        ((-0.05 -0.015  0.005) bottomAir)
    );

locationsInMesh

(

(( 0.005 0.005 0.005) heater)

(( 0.05 0.005 0.005) rightSolid)

((-0.05 0.005 0.005) leftSolid)

((-0.05 0.015 0.005) topAir)

((-0.05 -0.015 0.005) bottomAir)

);

これによりsnappyHexMeshを実行するとstl面で区切られた部分の領域は名前が付けられたcellZoneができます。

snappyHexMesh -overwrite

1	snappyHexMesh -overwrite

constant/polyMesh/cellZones

5
(heater
{
    type            cellZone;
    cellLabels      List<label> 
640
...
(省略)
...
163
166
)
;
}
leftSolid
{
    type            cellZone;
    cellLabels      List<label> 
1040
(
150
...
(省略)
...

(heater

{

type cellZone;

cellLabels List<label>

640

...

(省略)

...

163

166

)

;

}

leftSolid

{

type cellZone;

cellLabels List<label>

1040

(

150

...

(省略)

...

こんな形でできています。
ParaViewで確認することもできます。

※以下補足です。
snappyHexMeshはstlファイルで区切られた領域のメッシュを作成するために、locationInMeshを使うことがあります。
試しに上記をコメントアウトして以下のようにしてsnappyHexMeshを実行してみます。

    //     (( 0.005 0.005  0.005) heater)
    //     (( 0.05  0.005  0.005) rightSolid)
    //     ((-0.05  0.005  0.005) leftSolid)
    //     ((-0.05  0.015  0.005) topAir)
    //     ((-0.05 -0.015  0.005) bottomAir)
    // );
    locationInMesh
    (
         0.005 0.005  0.005
    );