[vivek_glasswala]

Hello Foamers,


i have met a problem while working on one of my project in OpenFoam, which is about the stratified tank.



I am trying to import the stratified injection pipe as a baffle geometry. (Original stl file to be seen in photo - Original_Stl.jpeg)


As a procedure, i did the blockMesh first then snappyHexMesh and then the createBaffles.



As i am importing it, it changes the shape from cylindrical geometry to box geometry. (Results are to be seen in photo - After_createBaffles-1&2)


Is there any possibility to improve the quality of the mesh on baffles. (Or is it not possible to even mesh the baffle manually!!!)


Here is the Dict file i used for my project:

snappyHexMeshDict:

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  8
     \\/     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
{
    tank_combined
    {
        type triSurfaceMesh;
        file "combined.stl"; //"wall.stl";
        
            regions
            {    
                inlet_links    { name inlet_links; }
                inlet_rechts    { name inlet_rechts; }
                outlet        { name outlet; }
                 wall        { name tank_wall; }
//                Baffle_links    { name Baffle_links; }
 //               Baffle_rechts    { name Baffle_rechts; }
       
            }
            
    }

    // Analytical shape; cylinder, sphere
    refinementBox
    {
        type searchableBox;
        min (-1.0 -0.7 0.0);
        max ( 8.0  0.7 2.5);
    }
    
};



// 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 7000000;

    // 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 "Baffle_links.extendedFeatureEdgeMesh";
            level 5;
        }
        
        {    
            file "Baffle_rechts.extendedFeatureEdgeMesh";
            level 5;
        }
        
        {
            file "combined.extendedFeatureEdgeMesh";
            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
    {
        tank_combined
        {
            // Surface-wise min and max refinement level
            level (2 3);
            
            regions
            {
               inlet_links    { level (2 3); patchInfo { type patch; }}
                inlet_rechts    { level (2 3); patchInfo { type patch; }}
                outlet        { level (2 3); patchInfo { type patch; }}
                wall        { level (2 3); patchInfo { type patch; }}
//                Baffle_links    { level (1 2); patchInfo { type patch; }}
//                Baffle_rechts    { level (1 2); patchInfo { type patch; }}
        }
        }
    }

    // Resolve sharp angles
    resolveFeatureAngle 60;


    // 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 (0 0 1.125);


    // 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 3.0;

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

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

    //- Number of feature edge snapping iterations.
    //  Leave out altogether to disable.
    nFeatureSnapIter 10;

    //- Detect (geometric only) features by sampling the surface
    //  (default=false).
    implicitFeatureSnap true;

    //- Use castellatedMeshControls::features (default = true)
    explicitFeatureSnap false;

    //- Detect points on multiple surfaces (only for explicitFeatureSnap)
    multiRegionFeatureSnap false;
}



// 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
    {
        "tank_wall"
        
        {
            nSurfaceLayers 3;
            mergeFaces false;
        }

/* 
        "Baffles_links"
        
        {
            nSurfaceLayers 3;
            mergeFaces false;
        }
        
        "Baffle_rechts"
        
        {
            nSurfaceLayers 3;
            mergeFaces false;
        }
        */        
    }

    // Expansion factor for layer mesh
    expansionRatio 1.0;

    // 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 0.3;

    // 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.
    nGrow 0;


    // Advanced settings

    // When not to extrude surface. 0 is flat surface, 90 is when two faces
    // are perpendicular
    featureAngle 60;

    // 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 0.3;

    // Angle used to pick up medial axis points
    minMedianAxisAngle 90;

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

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

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


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

createBafflesDict

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  8
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      createBafflesDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Whether to convert internal faces only (so leave boundary faces intact).
// This is only relevant if your face selection type can pick up boundary
// faces.
internalFacesOnly true;

fields true;

// Baffles to create.
baffles
{
    Baffle_links
    {
        //- Use predefined faceZone to select faces and orientation.
        type        searchableSurface;
        surface     triSurfaceMesh;
        name        Baffle_links.stl;

        patchPairs
        {
            type            wall;
            patchFields
            {
                #include "./0/include/wallBafflePatches"
                #include "./0/include/1DBaffle/1DTemperatureMasterBafflePatches"
            }
        }
    }
    Baffle_rechts
    {
        //- Use predefined faceZone to select faces and orientation.
        type        searchableSurface;
        surface     triSurfaceMesh;
        name        Baffle_rechts.stl;

        patchPairs
        {
            type            wall;
            patchFields
            {
                #include "./0/include/wallBafflePatches"
                #include "./0/include/1DBaffle/1DTemperatureMasterBafflePatches"
            }
        }
    }
   
}


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

Original_Stl.jpeg

After_createBaffles-1.jpeg

After_createBaffles-2.jpeg