[WaterHammer1985]

Hello,

I am meshing steps (see below for image = steps.png). All of the steps are the same and the edges developed using surfaceFeatureExtract appear correct (image = stepsWithEdges.png). The mesh captures some of the steps correctly (image = cornerCaptured.png). The mesh doesn't capture all of the steps correctly (image = cornerNotCaptured.png). I've tried combinations of all snapControls that I know of and can't get them all captured correctly, any hints/suggestions would be greatly appreciated.

Note: The edges of interest (red and green in image=stepsWithEdges.png) are wall1 and conc, respectively.


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
{
    inlet_water
    {
        type triSurfaceMesh;
        file "inlet_waterc.stl";
    }
    
    outlet_water
    {
        type triSurfaceMesh;
        file "outlet_waterc.stl";
    }
    inlet_wall
    {
        type triSurfaceMesh;
        file "inlet_wallc.stl";
    }

    outlet_air
    {
        type triSurfaceMesh;
        file "outlet_airc.stl";
    }

    bed1
    {
        type triSurfaceMesh;
        file "bed1c.stl";
    }
    bed2
    {
        type triSurfaceMesh;
        file "bed2c.stl";
    }
    conc
    {
        type triSurfaceMesh;
        file "concc.stl";
    }

    wall1
    {
        type triSurfaceMesh;
        file "wall1c.stl";
    }

    
    wall2
    {
        type triSurfaceMesh;
        file "wall2c.stl";
    }
    
    top
    {
        type triSurfaceMesh;
        file "topc.stl";
    }

    refinementBox1
    {
        type searchableBox;
        min (400 270 0);
        max (420 550 438);
    }
 
 
    refinementBox2
    {
        type searchableBox;
        min (400 -11350 0);
        max (420 306.5 461);
    }
   


};



// 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 100000000;

    // 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
    (
        {
            file "inlet_waterc.eMesh";
            level 0;
        }
         {
            file "outlet_waterc.eMesh";
            level 0;
        }
         {
            file "topc.eMesh";
            level 0;
        }
         {
            file "bed1c.eMesh";
            level 0;
        }
         {
            file "bed2c.eMesh";
            level 0;
        }

         {
            file "wall1c.eMesh";
            level 1;
        }
         {
            file "wall2c.eMesh";
            level 1;
        }
        {
            file "topc.eMesh";
            level 0;
        }
        {
            file "concc.eMesh";
            level 5;
        }
        {
            file "inlet_wallc.eMesh";
            level 0;
        }
         {
            file "outlet_airc.eMesh";
            level 0;
        }




 );



    // 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
    {
        inlet_water {level (1 1);}
        outlet_water {level (0 0);}
        inlet_wall {level (1 1);}
        outlet_air {level (1 1);}
        top {level (0 0);}
        bed1 {level (0 0);}
        bed2 {level (3 3);}
        wall1 {level (0 0);}
        wall2 {level (0 0);}
	conc {level (4 4);}
    }


    // Resolve sharp angles
    resolveFeatureAngle 10;  //default 30 anything above this number gets resolved i.e. increase above 90 to not capture corners


    // 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 distance;
            levels ((0.001 4) (0.01 3) (0.1 2));   //was  levels ((1E15 4))
        }
       */

       
       refinementBox1
       {
       mode inside;
       levels ((0.05 2));
       }


       refinementBox2
       {
       mode inside;
       levels ((0.05 2));
       }

	conc
       {
       mode distance;
       levels ( (0.625 4) (1.875 3) (4.375 2) );
       }

    }


    // 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 (406.222344 317.532332 461.32220232);


    // 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 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;

    // Feature snapping

        //- Number of feature edge snapping iterations.
        //  Leave out altogether to disable.
        nFeatureSnapIter 30;

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

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

        //- 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
    // "(wall1|wall2).*"
    layers
    {
        "(conc).*"
        {
            nSurfaceLayers 3;
        }
    }

    // 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 0.15;

    // 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
    // are perpendicular
    featureAngle 60;

    // At non-patched sides allow mesh to slip if extrusion direction makes
    // angle larger than slipFeatureAngle.
    slipFeatureAngle 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
{
    #include "meshQualityDict"


    // Advanced

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


// Advanced

// Write flags
writeFlags
(
    scalarLevels
    layerSets
    layerFields     // write volScalarField for layer coverage
);


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

meshQualityDict

// Include defaults parameters from master dictionary
#includeEtc "caseDicts/meshQualityDict"

//- minFaceWeight (0 -> 0.5)
minFaceWeight 0.02;

[Carlo_P]

Hey,

what I can suggest is to:


-increase the refinement level of the feature, in particolar of the wall1


- decrease the number of minRefinementCells, in order to be sure that snappy wiill make all the refinements (you can also read it on the log)


- decrease the value of resolveFeatureAngle. Theoretically should be this command that control the angle.


Let me know!

[WaterHammer1985]

Thank you for the suggestions. It is still having problem areas (images attached). All of the stairs appear to be identical when viewing the ~/constant/extendedFeatureEdgeMesh/ files. I've also tried shifting and increasing/decreasing the size of blockMesh. Any additional suggestions would be greatly appreciated!


-increase the refinement level of the feature, in particular of the wall1
---increased to level 2 (0.062m nominal cell size; step length is 1.7m for reference)

- decrease the number of minRefinementCells, in order to be sure that snappy will make all the refinements (you can also read it on the log)
---decreased from 10 to 1

- decrease the value of resolveFeatureAngle. Theoretically should be this command that control the angle.
---decreased from 20 to 5

Updated snapphexMeshDict:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5                                     |
|   \\  /    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
{
    inlet_water
    {
        type triSurfaceMesh;
        file "inlet_waterc.stl";
    }
    
    outlet_water
    {
        type triSurfaceMesh;
        file "outlet_waterc.stl";
    }
    inlet_wall
    {
        type triSurfaceMesh;
        file "inlet_wallc.stl";
    }

    outlet_air
    {
        type triSurfaceMesh;
        file "outlet_airc.stl";
    }

    bed1
    {
        type triSurfaceMesh;
        file "bed1c.stl";
    }
    bed2
    {
        type triSurfaceMesh;
        file "bed2c.stl";
    }
    conc
    {
        type triSurfaceMesh;
        file "concc.stl";
    }

    wall1
    {
        type triSurfaceMesh;
        file "wall1c.stl";
    }

    
    wall2
    {
        type triSurfaceMesh;
        file "wall2c.stl";
    }
    
    top
    {
        type triSurfaceMesh;
        file "topc.stl";
    }

    refinementBox_TW
    {
        type searchableBox;
        min (400 270 0);
        max (420 550 438);
    }
 
 
    refinementBox_HW
    {
        type searchableBox;
        min (400 -11350 0);
        max (420 306.5 461);
    }
   
};

// 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 100000000;

    // 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 1; //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 4;



    // 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 "inlet_waterc.eMesh";
            level 0;
        }
         {
            file "outlet_waterc.eMesh";
            level 0;
        }
         {
            file "topc.eMesh";
            level 0;
        }
         {
            file "bed1c.eMesh";
            level 0;
        }
         {
            file "bed2c.eMesh";
            level 0;
        }

         {
            file "wall1c.eMesh";
            level 2;
        }
         {
            file "wall2c.eMesh";
            level 2;
        }
        {
            file "topc.eMesh";
            level 0;
        }
        {
            file "concc.eMesh";
            level 4;
        }
        {
            file "inlet_wallc.eMesh";
            level 0;
        }
         {
            file "outlet_airc.eMesh";
            level 0;
        }




 );



    // 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
    {
        inlet_water {level (1 1);}
        outlet_water {level (1 1);}
        inlet_wall {level (1 1);}
        outlet_air {level (1 1);}
        top {level (0 0);}
        bed1 {level (0 0);}
        bed2 {level (4 4);}
        wall1 {level (2 2);}
        wall2 {level (2 2);}
	conc {level (4 4);}
    }


    // Resolve sharp angles
    resolveFeatureAngle 5;  //default 30 anything above this number gets resolved i.e. increase above 90 to not capture corners


    // 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 distance;
            levels ((0.001 4) (0.01 3) (0.1 2));   //was  levels ((1E15 4))
        }
       */

       
       refinementBox_TW
       {
       mode inside;
       levels ((0.05 3));
       }


       refinementBox_HW
       {
       mode inside;
       levels ((0.05 2));
       }
       

	conc
       {
       mode distance;
       levels ( (3 4) (4 3) (5 2) );
       }


       
    }


    // 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 (406.222344 317.532332 461.32220232);


    // 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 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;

    // 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 false;

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

        //- 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
    {
        "(conc|bed2).*"
        {
            nSurfaceLayers 2;
        }
    }

    // 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 0.2;

    // 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
    // are perpendicular
    featureAngle 60;

    // At non-patched sides allow mesh to slip if extrusion direction makes
    // angle larger than slipFeatureAngle.
    slipFeatureAngle 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
{
    #include "meshQualityDict"


    // Advanced

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


// Advanced

// Write flags
writeFlags
(
    scalarLevels
    layerSets
    layerFields     // write volScalarField for layer coverage
);


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


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

[WaterHammer1985]

Update: The issue was resolved by setting "implicitFeatureSnap true;" and "explicitFeatureSnap false;"