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ENH: tutorial cvMeshDict: updated with comment

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mattijs
2011-06-21 18:33:20 +01:00
parent 26d3e26639
commit 5d9d728128
1 changed files with 198 additions and 38 deletions
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236
tutorials/mesh/cvMesh/simpleShapes/system/cvMeshDict
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@ -10,12 +10,6 @@ FoamFile
{
version 2.0;
format ascii;
root "";
case "";
instance "";
local "";
class dictionary;
object cvMeshDict;
}
@ -23,6 +17,31 @@ FoamFile
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
/*
Control dictionary for cvMesh - polyhedral mesh generator.
cvMesh phases:
1. fill volume with initial points (initialPoints subdictionary). An option
is to reread from previous set of points.
2. internal point motion (motionControl subdictionary)
3. every once in a while add point duplets/triplets to conform to
surfaces and features (surfaceConformation subdictionary)
4. back to 2
5. construct polyMesh.
- filter (polyMeshFiltering subdictionary)
- check (meshQualityControls subdictionary) and undo filtering
See also cvControls.H in the conformalVoronoiMesh library
*/
// Important:
// ----------
// Any scalar with a name <name>Coeff specifies a value that will be implemented
@ -39,75 +58,105 @@ FoamFile
geometry
{
// Internal shape
coneAndSphere.obj
coneAndSphere_clean_orient.obj
{
name coneAndSphere;
type triSurfaceMesh;
tolerance 0.00001;
}
// // Internal shape
// coneAndSphere
// {
// type searchableSurfaceWithGaps;
// surface coneAndSphere.obj;
// gap 0.001;
// }
// Bounds of domain
domain.stl
// Outside of domain
domain_clean_orient.stl
{
name domain;
type triSurfaceMesh;
}
}
// Controls for conforming to the surfaces.
surfaceConformation
{
// Point that is inside wanted part of geometry.
// A point inside surfaces that is inside mesh.
locationInMesh (0 -0.5 0);
// Balance this between
// How far apart are point-duplets generated. Balance this between
// - very low distance: little chance of interference from other
// surfaces
// - largish distance: less non-orthogonality in final cell
// (circumcentre far away from centroid)
pointPairDistanceCoeff 0.1;
// Mixed feature edges - both inside and outside edges. Recreated
// by inserting triplets of points to recreate a single edge. Done for
// all edges emanating from point. triplets of points get inserted
// mixedFeaturePointPPDistanceCoeff distance away from feature point.
mixedFeaturePointPPDistanceCoeff 5.0;
// Distance to a feature point within which surface and edge
// conformation points are excluded - fraction of the local target
// cell size
featurePointExclusionDistanceCoeff 0.4;
// Distance to an existing feature edge conformation location
// within which other edge conformation location are excluded -
// fraction of the local target cell size
featureEdgeExclusionDistanceCoeff 0.2;
// Optimisation: do not check for surface intersection (of dual edges)
// for points near to surface.
surfaceSearchDistanceCoeff 2.5;
// Maximum allowable protrusion through the surface before
// conformation points are added - fraction of the local target
// cell size. These small protusions are (hopefully) done by mesh filtering
// instead.
maxSurfaceProtrusionCoeff 0.1;
// If feature edge with large angle (so more than 125 degrees) introduce
// additional points to create two half angled cells (= mitering).
maxQuadAngle 125;
// Frequency to redo surface conformation (expensive).
surfaceConformationRebuildFrequency 10;
// Initial and intermediate controls
coarseConformationControls
{
// Initial conformation
initial
{
// We've got a point poking through the surface. Don't do any
// surface conformation if near feature edge (since feature edge
// conformation should have priority)
// distance to search for near feature edges
edgeSearchDistCoeff 1.1;
// Proximity to a feature edge where a surface hit is
// not created, only the edge conformation is created
// - fraction of the local target cell size. Coarse
// conformation, initial protrusion tests.
surfacePtReplaceDistCoeff 0.5;
}
// Same for iterations
iteration
{
edgeSearchDistCoeff 1.25;
surfacePtReplaceDistCoeff 0.7;
}
// Stop either at maxIterations or if the number of surface pokes
// is very small (iterationToInitialHitRatioLimit * initial number)
// Note: perhaps iterationToInitialHitRatioLimit should be absolute
// count?
maxIterations 15;
iterationToInitialHitRatioLimit 0.001;
}
// Final (at endTime) controls
fineConformationControls
{
initial
@ -127,45 +176,49 @@ surfaceConformation
iterationToInitialHitRatioLimit 0.001;
}
// Geometry to mesh to
geometryToConformTo
{
coneAndSphere
{
featureMethod extendedFeatureEdgeMesh;
extendedFeatureEdgeMesh "coneAndSphere.extendedFeatureEdgeMesh";
extendedFeatureEdgeMesh "coneAndSphere_clean_orient.extendedFeatureEdgeMesh";
}
domain.stl
domain
{
featureMethod extendedFeatureEdgeMesh;
extendedFeatureEdgeMesh "domain.extendedFeatureEdgeMesh";
extendedFeatureEdgeMesh "domain_clean_orient.extendedFeatureEdgeMesh";
}
}
additionalFeatures {}
}
// Controls for seeding initial points and general control of the target
// cell size (used everywhere)
initialPoints
{
// Do not place point closer than minimumSurfaceDistanceCoeff
// to the surface. Is fraction of local target cell size (see below)
minimumSurfaceDistanceCoeff 0.55;
initialPointsMethod autoDensity;
// initialPointsMethod uniformGrid;
// initialPointsMethod bodyCentredCubic;
// initialPointsMethod pointFile;
initialPointsMethod autoDensity;
// initialPointsMethod uniformGrid;
// initialPointsMethod bodyCentredCubic;
// initialPointsMethod pointFile;
// Take boundbox of all geometry. Samples with this box. If too much
// samples (due to target cell size) in box split box.
// Take boundbox of all geometry. Sample with this box. If too much
// samples in box (due to target cell size) split box.
autoDensityDetails
{
// Number of refinement levels. Needs to be enough to pick up features
// due to size ratio.
minLevels 2;
// Split box if ratio of min to max size larger than maxSizeRatio
// Initial number of refinement levels. Needs to be enough to pick
// up features due to size ratio. If not enough it will take longer
// to determine point seeding.
minLevels 4;
// Split box if ratio of min to max cell size larger than maxSizeRatio
maxSizeRatio 5.0;
// Per box sample 3x3x3 internally
sampleResolution 3;
@ -175,6 +228,7 @@ initialPoints
uniformGridDetails
{
// Absolute cell size.
initialCellSize 0.0015;
randomiseInitialGrid yes;
randomPerturbationCoeff 0.02;
@ -189,13 +243,25 @@ initialPoints
pointFileDetails
{
// Reads points from file. Still rejects points that are too
// close to the surface (minimumSurfaceDistanceCoeff) or on the
// wrong side of the surfaces.
pointFile "constant/internalDelaunayVertices";
}
}
// Control size of voronoi cells i.e. distance between points. This
// determines the target cell size which is used everywhere.
// It determines the cell size given a location. It then uses all
// the rules
// - defaultCellSize
// - cellSizeControlGeometry
// to determine target cell size. Rule with highest priority wins. If same
// priority smallest cell size wins.
motionControl
{
// Absolute cell size of back ground mesh. This is the maximum cell size.
defaultCellSize 0.1;
// Assign a priority to all requests for cell sizes, the highest overrules.
@ -205,7 +271,11 @@ motionControl
{
}
relaxationModel adaptiveLinear;
// Underrelaxation for point motion. Simulated annealing: starts off at 1
// and lowers to 0 (at simulation endTime) to converge points.
// adaptiveLinear is preferred choice.
// Points move by e.g. 10% of tet size.
relaxationModel adaptiveLinear; //rampHoldFall
adaptiveLinearCoeffs
{
@ -213,28 +283,57 @@ motionControl
relaxationEnd 0.0;
}
// Output lots and lots of .obj files
objOutput no;
// Timing and memory usage.
timeChecks yes;
// Number of rays in plane parallel to nearest surface. Used to detect
// next closest surfaces. Used to work out alignment (three vectors)
// to surface.
// Note that only the initial points (from the seeding) calculate this
// information so if these are not fine enough the alignment will
// not be correct. (any points added during the running will lookup
// this information from the nearest initial point since it is
// expensive)
alignmentSearchSpokes 36;
// For each delaunay edge (between two vertices, becomes
// the Voronoi face normal) snap to the alignment direction if within
// alignmentAcceptanceAngle. Slightly > 45 is a good choice - prevents
// flipping.
alignmentAcceptanceAngle 48;
// How often to rebuild the alignment info (expensive)
sizeAndAlignmentRebuildFrequency 20;
// When to insert points. Not advisable change to
// these settings.
pointInsertionCriteria
{
// If edge larger than 1.75 target cell size
// (so tets too large/stretched) insert point
cellCentreDistCoeff 1.75;
// Do not insert point if voronoi face (on edge) very small.
faceAreaRatioCoeff 0.0025;
// Insert point only if edge closely aligned to local alignment
// direction.
acceptanceAngle 21.5;
}
// Opposite: remove point if mesh too compressed. Do not change these
// settings.
pointRemovalCriteria
{
cellCentreDistCoeff 0.65;
}
// How to determine the point motion. All edges got some direction.
// Sum all edge contributions to determine point motion. Weigh by
// face area so motion is preferentially determined by large faces
// (or more importantly ignore contribution from small faces).
// Do not change these settings.
faceAreaWeightModel piecewiseLinearRamp;
piecewiseLinearRampCoeffs
@ -245,34 +344,95 @@ motionControl
}
// After simulation, when converting to polyMesh, filter out small faces/edges.
// Do not change. See cvControls.H
polyMeshFiltering
{
// Upper limit on the size of faces to be filtered.
// fraction of the local target cell size
filterSizeCoeff 0.2;
mergeClosenessCoeff 1e-4;
// Upper limit on how close two dual vertices can be before
// being merged, fraction of the local target cell size
mergeClosenessCoeff 1e-9;
// To not filter: set maxNonOrtho to 1 (so check fails) and then
// set continueFilteringOnBadInitialPolyMesh to false.
continueFilteringOnBadInitialPolyMesh true;
// When a face is "bad", what fraction should the filterSizeCoeff be
// reduced by. Recursive, so for a filterCount value of fC, the
// filterSizeCoeff is reduced by pow(filterErrorReductionCoeff, fC)
filterErrorReductionCoeff 0.5;
// Maximum number of filterCount applications before a face
// is not attempted to be filtered
filterCountSkipThreshold 4;
// Maximum number of permissible iterations of the face collapse
// algorithm. The value to choose will be related the maximum number
// of points on a face that is to be collapsed and how many faces
// around it need to be collapsed.
maxCollapseIterations 25;
// Maximum number of times an to allow an equal faceSet to be
// returned from the face quality assessment before stopping iterations
// to break an infinitie loop.
maxConsecutiveEqualFaceSets 5;
// Remove little steps (almost perp to surface) by collapsing face.
surfaceStepFaceAngle 80;
// Do not collapse face to edge if should become edges
edgeCollapseGuardFraction 0.3;
// Only collapse face to point if high aspect ratio
maxCollapseFaceToPointSideLengthCoeff 0.35;
}
// Generic mesh quality settings. At any undoable phase these determine
// where to undo. Same as in snappyHexMeshDict
meshQualityControls
{
//- Maximum non-orthogonality allowed. Set to 180 to disable.
maxNonOrtho 65;
//- Max skewness allowed. Set to <0 to disable.
maxBoundarySkewness 50;
maxInternalSkewness 10;
//- 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 quality of the tet formed by the
// variable base point minimum decomposition triangles and
// the cell centre (so not face-centre decomposition).
// This has to be a positive number for tracking
// to work. Set to very negative number (e.g. -1E30) to
// disable.
// <0 = inside out tet,
// 0 = flat tet
// 1 = regular tet
minTetQuality 1e-30;
minVol 0;
//- Minimum absolute face area. Set to <0 to disable.
minArea -1;
minTwist 0.02;
//- Minimum face twist. Set to <-1 to disable. dot product of face normal
//- and face centre triangles normal
minTwist 0.001;
//- 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;
}