| christos |
December 16, 2014 10:35 |
meshing of very small patches in comparison with the overall geometry
2 Attachment(s)
Hi everyone,
I have a problem on meshing very small stl surfaces that coexists with bigger stl surfaces. Please find below a description of my problem:
There is a big room (dimensions 15x11x3 m). Outside of the room there is a gas heater which transfers hot air inside the room through a pipe installation. The part of the pipe that is inside the room has small holes, hence hot air escapes from these holes and warms the room. For simplification purposes I want to first model my case from these small holes and afterwards (later on I will include the pipe installation). Hence, I create .stl surfaces for the room and for these small holes. Now the problem is that snappyHexMesh does a very bad coarse refinement in the region of these small holes, despite the fact that I increase the edge refinement level and the surface refinement.
In addition these small holes (hotInlets) are defined as faceZones in the SHM dictionary.
Thanks a lot for your help!!!
SnappyHexMeshDict
Code:
castellatedMesh true;
snap true;
addLayers true;
geometry
{
roomWalls.stl
{
type triSurfaceMesh;
name roomWalls;
}
hotInlet1.stl
{
type triSurfaceMesh;
name hotInlet1;
}
hotInlet2.stl
{
type triSurfaceMesh;
name hotInlet2;
}
hotInlet3.stl
{
type triSurfaceMesh;
name hotInlet3;
}
hotInlet4.stl
{
type triSurfaceMesh;
name hotInlet4;
}
hotInlet5.stl
{
type triSurfaceMesh;
name hotInlet5;
}
hotInlet6.stl
{
type triSurfaceMesh;
name hotInlet6;
}
outlet1.stl
{
type triSurfaceMesh;
name outlet1;
}
outlet2.stl
{
type triSurfaceMesh;
name outlet2;
}
outlet3.stl
{
type triSurfaceMesh;
name outlet3;
}
roomVolume.stl
{
type triSurfaceMesh;
name roomVolume;
}
};
// Settings for the castellatedMesh generation.
castellatedMeshControls
{
maxLocalCells 1000000;
maxGlobalCells 2000000;
minRefinementCells 0;
nCellsBetweenLevels 1;
features
(
{
file "roomWalls.eMesh";
level 1;
}
{
file "hotInlet1.eMesh";
level 3;
}
{
file "hotInlet2.eMesh";
level 3;
}
{
file "hotInlet3.eMesh";
level 3;
}
{
file "hotInlet4.eMesh";
level 3;
}
{
file "hotInlet5.eMesh";
level 3;
}
{
file "hotInlet6.eMesh";
level 3;
}
{
file "outlet1.eMesh";
level 1;
}
{
file "outlet2.eMesh";
level 1;
}
{
file "outlet3.eMesh";
level 1;
}
);
refinementSurfaces
{
roomWalls
{
// Surface-wise min and max refinement level
level (1 1);
patchInfo
{
type wall;
//inGroups (hotOutlet);
}
}
outlet1
{
// Surface-wise min and max refinement level
level (1 1);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
}
outlet2
{
// Surface-wise min and max refinement level
level (1 1);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
}
outlet3
{
// Surface-wise min and max refinement level
level (1 1);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
}
hotInlet1
{
// Surface-wise min and max refinement level
level (3 3);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
faceZone hotInlet1;
faceType baffle;
}
hotInlet2
{
// Surface-wise min and max refinement level
level (3 3);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
faceZone hotInlet2;
faceType baffle;
}
hotInlet3
{
// Surface-wise min and max refinement level
level (3 3);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
faceZone hotInlet3;
faceType baffle;
}
hotInlet4
{
// Surface-wise min and max refinement level
level (3 3);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
faceZone hotInlet4;
faceType baffle;
}
hotInlet5
{
// Surface-wise min and max refinement level
level (3 3);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
faceZone hotInlet5;
faceType baffle;
}
hotInlet6
{
// Surface-wise min and max refinement level
level (3 3);
patchInfo
{
type patch;
//inGroups (hotOutlet);
}
faceZone hotInlet6;
faceType baffle;
}
}
// Resolve sharp angles
resolveFeatureAngle 30;//30
refinementRegions
{
}
locationInMesh (0.00001123 0.1 0.1);
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;//1
//- Number of mesh displacement relaxation iterations.
nSolveIter 30;//300
//- 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;
//- Detect (geometric) features by sampling the surface
implicitFeatureSnap false;
//- Use castellatedMeshControls::features
explicitFeatureSnap true;
//- Detect features between multiple surfaces
// (only for explicitFeatureSnap, default = false)
multiRegionFeatureSnap true;
}
// Settings for the layer addition.
addLayersControls
{
relativeSizes true;
// Per final patch (so not geometry!) the layer information
layers
{
/*maxY
{
nSurfaceLayers 1;
}*/
}
// 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.
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 0.25;
// 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 1;//0
// Advanced settings
// When not to extrude surface. 0 is flat surface, 90 is when two faces
// are perpendicular
featureAngle 60;//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 130;//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;
nRelaxedIter 20;
}
// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
#include "meshQualityDict"
maxNonOrtho 75;
maxBoundarySkewness 20;
maxConcave 80;
minFlatness 0.5;
minVol 1e-13;
minArea -1;
minTwist 0.05;
minDeterminant 0.001;
minFaceWeight 0.05;
minVolRatio 0.01;
minTriangleTwist -1;
//- 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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