[mc6421]

https://drive.google.com/file/d/1LfU...ew?usp=sharing

Hi,

I have square block and ground surface layers. How do I get both ground inflation and the square block inflation to connect.

Please see the images above in the google drive link.

Help is much appreciated.






Snappy Hex Dic

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object autoHexMeshDict;
}

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

// 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
{
cylinder.stl
{
type triSurfaceMesh;
name cylinder;
}

refinementBox
{
type searchableBox;
min (-1.0 -2.5 0.0);
max ( 10.0 2.5 2.5);
}

refinementBox2
{
type searchableBox;
min (-9.15 -1.5 0.0);
max (-1 1.5 2.5);
}

refinementBox3
{
type searchableBox;
min (10 -2.5 0.0);
max ( 36.0 2.5 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 200000;

// 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 10000000;

// 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 2;

// Number of buffer layers between different levels.
// 1 means normal 2:1 refinement restriction, larger means slower
// refinement.
nCellsBetweenLevels 10;



// 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 "cylinder.eMesh";
level 3;
}
);



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

resolveFeatureAngle 20;


// 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 ((1 2));
}

refinementBox2
{
mode inside;
levels ((1 2));
}

refinementBox3
{
type searchableBox;
mode inside;
levels ((0 1));
}

}




// 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.
// This is an outside point locationInMesh (-0.033 -0.033 0.0033);
locationInMesh (5 1 2); // Inside point

// 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 2.0;

//- 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
{
"(ground|cylinder).*"
{
nSurfaceLayers 10;
expansionRatio 1.2;
finalLayerThickness 0.8;
minThickness 0.1;







}
}


layers
{

"(cylinder).*"
{
nSurfaceLayers 10;
expansionRatio 1.2;
finalLayerThickness 0.8;
minThickness 0.1;



}
}




// 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.
// See relativeSizes parameter.
finalLayerThickness 0.4;

// Minimum thickness of cell layer. If for any reason layer
// cannot be above minThickness do not add layer.
// See relativeSizes parameter.
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;


// 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 5;

// 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. Set to very negative number (e.g. -1E30) to
// disable.
// <0 = inside out tet,
// 0 = flat tet
// 1 = regular tet
minTetQuality 1e-9;

//- 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;

//- if >0 : preserve single cells with all points on the surface if the
// resulting volume after snapping (by approximation) is larger than
// minVolCollapseRatio times old volume (i.e. not collapsed to flat cell).
// If <0 : delete always.
//minVolCollapseRatio 0.5;


// Advanced

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



// Optional : some meshing phases allow usage of relaxed rules.
// See e.g. addLayersControls::nRelaxedIter.
relaxed
{
//- Maximum non-orthogonality allowed. Set to 180 to disable.
maxNonOrtho 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;

// 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;


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

Block Mesh

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;

vertices //list of vertices defining the geometry
(
(-9.15 -9.15 0) //This is point 0. Not 1!
(36.60 -9.15 0) //This is point 1
(36.60 9.15 0) //point 2
(-9.15 9.15 0) //point 3
(-9.15 -9.15 9.15) //point 4
(36.60 -9.15 9.15) //point 5
(36.60 9.15 9.15) //point 6
(-9.15 9.15 9.15) //point 7
);

blocks //defining the block which the geometry is made out of
(
hex (0 1 2 3 4 5 6 7) (100 50 25) simpleGrading
( (
(0.2 0.2 0.33)
(0.8 0.8 3)
)
(
(0.5 0.5 0.33) // 20% y-dir, 30% cells, expansion = 1
(0.5 0.5 3) // 20% y-dir, 30% cells, expansion = 4 (4)
)
(
1
)
)
//this means that the only block in the geometry is defined by vertices (0 1 2 ...), there are 100, 10
//and 1 cells in the x, y, and z direction and that in each direction all the cells have the same length
);

edges
(
// spline 0 1
// (
// (5 -2 0)
// )
// spline 4 5
// (
// (5 -2 0.1)
// )
);

boundary
(
walls //choose a name for the boundary
{
type wall; //define the type of the boundary
faces
(
(0 4 5 1) //list the faces; vertices should be listed in clockwise direction, as seen from the block
(2 6 7 3)
);
}


ground
{
type wall;
faces
(
(1 2 3 0)
);
}

sky
{
type wall;
faces
(
(7 6 5 4)

);
}

inlet
{
type patch;
faces
(
(3 7 4 0)
);
}


outlet
{
type patch;
faces
(
(2 1 5 6)
);
}



);


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

[AtoHM]

Attach images directly to the forum pls.



My first thought is: increase featureAngle in addLayersControls. As you wrote cube (and I did not click on the link), I assume the to-merge-layers are perpendicular, so featureAngle should be above 90 deg, try 100?

[apek_great]

Hi, I have the same problem. I am using snappyhexmesh with OF dev. I want to add layers (5 layers) around a cube that is mounted on a floor. However, the boundary layer has collapsed near the bottom edge of the cube attached on the floor (refer to the figures attached).


Anyone here have suggestions for improvement?

castellatedMesh true;
snap true;
addLayers true;

geometry
{
building
{
type triSurfaceMesh;
file "model.stl";
}
};

castellatedMeshControls
{
// Refinement parameters
// ~~~~~~~~~~~~~~~~~~~~~
maxLocalCells 100000;
maxGlobalCells 2000000;
minRefinementCells 10;
maxLoadUnbalance 0.10;
nCellsBetweenLevels 3;

// Explicit feature edge refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
features
(
{
file "model.eMesh";
level 0;
}
);

// Surface based refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~
refinementSurfaces
{
building
{
level (3 3);
}
}

resolveFeatureAngle 30;

// Region-wise refinement
// ~~~~~~~~~~~~~~~~~~~~~~
refinementRegions
{

}

// Mesh selection
// ~~~~~~~~~~~~~~
locationInMesh (0 1.2 0);
allowFreeStandingZoneFaces true;
}

snapControls
{
nSmoothPatch 3;
tolerance 2.0;
nSolveIter 30;
nRelaxIter 5;

// Feature snapping
nFeatureSnapIter 10;
implicitFeatureSnap false;
explicitFeatureSnap true;
multiRegionFeatureSnap false;
}

addLayersControls
{
relativeSizes false;

layers
{
"(building).*"
{
nSurfaceLayers 5;
}
"(floor).*"
{
nSurfaceLayers 5;
firstLayerThickness 0.005;
}
}
expansionRatio 1.1;
firstLayerThickness 0.0025;
minThickness 1e-16;
nGrow 0;

// Advanced settings
featureAngle 300;
slipFeatureAngle 30;
nRelaxIter 3;
nSmoothSurfaceNormals 1;
nSmoothNormals 3;
nSmoothThickness 10;
maxFaceThicknessRatio 0.5;
maxThicknessToMedialRatio 0.3;
minMedianAxisAngle 90;
nBufferCellsNoExtrude 0;
nLayerIter 50;
}

meshQualityControls
{
#include "meshQualityDict"
}

writeFlags
(
scalarLevels
layerSets
layerFields
);

mergeTolerance 1e-6;

[AtoHM]

You specified different sizes for the layers which require transitions of the layers size, exactly in a delicate spot (the corner) and spatially close transitions of refinement levels.

Keep in mind: growing layers is a difficult taks for snappy and you have to make it as easy as possible. In your example, the local cell level does vary greatly between your cube and the lower face and the transitions between the levels are close together. snappy will have the best chances, if these faces had the same level and the layers had the same size. If thats not possible, try to make some more space between the transitions by increasing the setting for nCellsBetweenLevels.