MBttR |
August 11, 2016 10:21 |
sHM layer process keeps getting killed
Hi,
I've succesfully completed the external flow research of an aircraft, rotors off, under all conditions I need. Results look meaningful. Wanting now to progress to a rotors on, MRF simulation, I'm having issues with snappyHexMesh and I'm starting to run out of things to try. First I had a very low quality mesh, but after tweaking surface and region refinement variables I got a good snap. I sometimes got a 'Killed' message but changing maxLocalCells and maxGlobalCells fixed that issue.
Now, however, I'm stuck at layers. I have tried changing the featureAngle, the amount of layers, the layer thicknesses, maxLocalCells and maxGlobalCells, .. It always results in the following error (full log later)
Code:
truncateDisplacement : Unextruded 3 faces due to non-consecutive vertices being extruded.
truncateDisplacement : Unextruded 7 faces due to stringed edges with inconsistent extrusion.
truncateDisplacement : Unextruded 0 faces due to non-consecutive vertices being extruded.
truncateDisplacement : Unextruded 0 faces due to stringed edges with inconsistent extrusion.
Setting up information for layer truncation ...
Killed
If I try to rerun it, but with castellating and snapping turned off (hence only layers), it does finish meshing (in about 13 seconds) but actually hasn't done anything, so I think there's something going wrong because of that and therefore I only run it fully.
Below is my snappyHexMeshDict, under that is the full sHM log.
Cheers! I hope someone can help me further cause I'm at a bit of a loss. I'm glad I got a good snap, now just have to get the next part.
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 4.0 |
| \\ / 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
{
AC.stl
{
type triSurfaceMesh;
name AC;
}
refinementBody
{
type searchableBox;
min (-0.4 -0.35 -0.15);
max ( 0.75 0.35 0.25);
}
refinementArm1
{
type searchableBox;
min (-0.8 -0.1 -0.05);
max (-0.2 0.1 0.15);
}
refinementArm2
{
type searchableBox;
min ( -0.1 0.2 -0.1);
max ( 0.1 0.75 0.1);
}
refinementArm3
{
type searchableBox;
min ( 0.25 -0.1 -0.1);
max ( 0.85 0.1 0.1);
}
refinementArm4
{
type searchableBox;
min ( -0.1 -0.75 -0.1);
max ( 0.1 -0.2 0.1);
}
gps
{
type searchableBox;
min ( -0.06 -0.015 -0.145);
max ( -0.03 0.015 0.165);
}
rotor1
{
type searchableCylinder;
point1 ( -0.65914769291 0 0.06);
point2 ( -0.65914769291 0 0.14);
radius 0.4;
}
/*rotor2
{
type searchableCylinder;
point1 ( 0 0.59384907717 0.04);
point2 ( 0 0.59384907717 0.08);
radius 0.4;
}
rotor3
{
type searchableCylinder;
point1 ( 0 -0.59384907717 0.04);
point2 ( 0 -0.59384907717 0.08);
radius 0.4;
}
rotor4
{
type searchableCylinder;
point1 ( 0.69501408945 0 0.027);
point2 ( 0.69501408945 0 0.067);
radius 0.4;
}*/
};
// 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 1000000;
// 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 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 "AC.eMesh";
level 4;
}
);
// 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
{
AC
{
// Surface-wise min and max refinement level
level (6 8);
// Optional specification of patch type (default is wall). No
// constraint types (cyclic, symmetry) etc. are allowed.
}
}
// Resolve sharp angles
resolveFeatureAngle 30;
// 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
{
refinementBody
{
mode inside;
levels ((1E15 3));
}
refinementArm1
{
mode inside;
levels ((1E15 3));
}
refinementArm2
{
mode inside;
levels ((1E15 5));
}
refinementArm3
{
mode inside;
levels ((1E15 3));
}
refinementArm4
{
mode inside;
levels ((1E15 3));
}
gps
{
mode inside;
levels ((1E15 3));
}
rotor1
{
mode inside;
levels ((1E15 5));
}
/*rotor2
{
mode inside;
levels ((1E15 6));
}
rotor3
{
mode inside;
levels ((1E15 6));
}
rotor4
{
mode inside;
levels ((1E15 6));
}*/
}
// 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 (0.39847 0.65104 0.4);
// 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
{
AC
{
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 0.3;
// 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 0.01;
// 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;
// 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.
// 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
// 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;
// ************************************************************************* //
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