Mirage12 |
August 26, 2013 07:47 |
Meshing of A380
Hello Foamers :)
I am meshing an aircraft "A380" using snappyHexMesh :)
Here is my snappyHexMeshDict:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.0 |
| \\ / 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 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
{
A380.stl
{
type triSurfaceMesh;
name A380;
}
box
{
type searchableBox;
min (-400 -400 -400);
max (400 400 400);
}
};
// 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 50000000;
// 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 50000000;
// 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;
// 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 "A380.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
{
A380
{
// Surface-wise min and max refinement level
level (5 6);
patchInfo
{
type wall;
inGroups (A380);//aircraft is the first line of our ASCII-STL file,
//it is the patch name
}
}
}
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
{
refinementBox
{
mode inside;
levels ((5 5) (5 5) (5 5));
}
}
// 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 (400 400 0);
// 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 4.0;
//- Number of mesh displacement relaxation iterations.
nSolveIter 0;
//- 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 0;
//- 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
{
A380
{
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.
// See relativeSizes parameter.
finalLayerThickness 0.3;
// Minimum thickness of cell layer. If for any reason layer
// cannot be above minThickness do not add layer.
// See relativeSizes parameter.
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 0;
// Advanced settings
// When not to extrude surface. 0 is flat surface, 90 is when two faces
// are perpendicular
featureAngle 60;
// 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 16x! 90 degrees corresponds to 130 in 16x.
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;
// Max number of iterations after which relaxed meshQuality controls
// get used. Up to nRelaxIter it uses the settings in meshQualityControls,
// after nRelaxIter it uses the values in meshQualityControls::relaxed.
nRelaxedIter 20;
}
// 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-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 0.05;
//- 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;
//- 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 cell
for postprocessing
// 4 : write current intersections as .obj files
debug 0;
// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1e-6;
// ************************************************************************* //
Here is my checkMesh
Code:
Create polyMesh for time = 0
Time = 0
Mesh stats
points: 3442951
faces: 10192500
internal faces: 10057500
cells: 3375000
faces per cell: 6
boundary patches: 3
point zones: 0
face zones: 0
cell zones: 0
Overall number of cells of each type:
hexahedra: 3375000
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 0
Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).
Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
inlet 22500 22801 ok (non-closed singly connected)
outlet 22500 22801 ok (non-closed singly connected)
fixedWalls 90000 90600 ok (non-closed singly connected)
Checking geometry...
Overall domain bounding box (-400 -400 -400) (400 400 400)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (1.02233e-18 -1.9688e-18 -1.96972e-18) OK.
Max cell openness = 1.31839e-16 OK.
Max aspect ratio = 1 OK.
Minimum face area = 28.4444. Maximum face area = 28.4444. Face area magnitudes OK.
Min volume = 151.704. Max volume = 151.704. Total volume = 5.12e+08. Cell volumes OK.
Mesh non-orthogonality Max: 0 average: 0
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 8.52655e-14 OK.
Coupled point location match (average 0) OK.
Mesh OK.
--> FOAM Warning :
From function polyMesh::readUpdateState polyMesh::readUpdate()
in file meshes/polyMesh/polyMeshIO.C at line 204
Number of patches has changed. This may have unexpected consequences. Proceed with care.
Time = 2
Mesh stats
points: 9781151
faces: 26102450
internal faces: 24511827
cells: 8169767
faces per cell: 6.19531
boundary patches: 4
point zones: 0
face zones: 0
cell zones: 0
Overall number of cells of each type:
hexahedra: 7656681
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 513086
Breakdown of polyhedra by number of faces:
faces number of cells
6 152595
8 2820
9 231859
10 517
11 870
12 80701
13 93
14 551
15 39670
16 6
17 59
18 3050
20 7
21 282
24 6
Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).
Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
inlet 22500 22801 ok (non-closed singly connected)
outlet 22500 22801 ok (non-closed singly connected)
fixedWalls 90000 90600 ok (non-closed singly connected)
A380_A380 1455623 1474663 ok (closed singly connected)
Checking geometry...
Overall domain bounding box (-400 -400 -400) (400 400 400)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (3.75772e-18 -2.8035e-18 -2.16765e-18) OK.
Max cell openness = 2.27306e-16 OK.
Max aspect ratio = 1.0084 OK.
Minimum face area = 0.0069139. Maximum face area = 28.4516. Face area magnitudes OK.
Min volume = 0.000576135. Max volume = 151.761. Total volume = 5.11996e+08. Cell volumes OK.
Mesh non-orthogonality Max: 25.3367 average: 7.36434
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 1.01205 OK.
Coupled point location match (average 0) OK.
Mesh OK.
Time = 4
Mesh stats
points: 9471318
faces: 25692830
internal faces: 24511827
cells: 8169767
faces per cell: 6.14518
boundary patches: 4
point zones: 0
face zones: 0
cell zones: 0
Overall number of cells of each type:
hexahedra: 7351909
prisms: 144354
wedges: 0
pyramids: 0
tet wedges: 2480
tetrahedra: 0
polyhedra: 671024
Breakdown of polyhedra by number of faces:
faces number of cells
4 91439
5 69428
6 150359
7 2362
8 1607
9 230819
10 386
11 767
12 80313
13 26
14 491
15 39627
16 4
17 56
18 3045
20 7
21 282
24 6
Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).
Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
inlet 22500 22801 ok (non-closed singly connected)
outlet 22500 22801 ok (non-closed singly connected)
fixedWalls 90000 90600 ok (non-closed singly connected)
A380_A380 1046003 1164830 ok (closed singly connected)
Checking geometry...
Overall domain bounding box (-400 -400 -400) (400 400 400)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (2.38306e-18 -2.72228e-18 5.44498e-18) OK.
Max cell openness = 3.17729e-16 OK.
Max aspect ratio = 5.66877 OK.
Minimum face area = 0.00025335. Maximum face area = 28.4516. Face area magnitudes OK.
Min volume = 2.74107e-05. Max volume = 151.761. Total volume = 5.11996e+08. Cell volumes OK.
Mesh non-orthogonality Max: 64.919 average: 7.95197
Non-orthogonality check OK.
Face pyramids OK.
***Max skewness = 6.52282, 71 highly skew faces detected which may impair the quality of the results
<<Writing 71 skew faces to set skewFaces
Coupled point location match (average 0) OK.
Failed 1 mesh checks.
End
As you see, the checkMesh mentioned that 1 mesh check failed.
I would like to ask you, if i can start the simulation despite this error ? and if yes how the error will affect my results .
Thank you for the support :)
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