| juvima |
January 7, 2020 07:17 |
Bad looking cells with CastelledMesh
3 Attachment(s)
Hello everybody, I'm struggling with some bad looking cells generated by the CastellatedMesh step of my snappyHexMeshDict file, cf. pictures. As you can see, some cells are extremely plane/crushed. I tried changing several parameters of my snappyHexMeshDict file, but the output doesn't change. This is my code:
Code:
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// Which of the steps to run
castellatedMesh true;
snap false;
addLayers false;
#include "include/inputVariables" //definition of input values
offset 1; //offset
x_positive #calc "3*$offset + $n_panel_x_dir*$x_panel";
x_negative #calc "-1*$offset";
y_positive #calc "0.5*$y_panel + $offset";
y_negative #calc "-1*$y_positive";
z_positive #calc "1.5*$offset";
// Geometry. Definition of all surfaces. All surfaces are of class
// searchableSurface.
// Surfaces are used
// - to specify refinement for any mesh cell intersecting it
// - to specify refinement for any mesh cell inside/outside/near
// - to 'snap' the mesh boundary to the surface
geometry
{
Panel_0
{
type triSurfaceMesh;
file "Panel_0.stl";
}
Panel_1
{
type triSurfaceMesh;
file "Panel_1.stl";
}
Panel_2
{
type triSurfaceMesh;
file "Panel_2.stl";
}
Panel_3
{
type triSurfaceMesh;
file "Panel_3.stl";
}
Panel_4
{
type triSurfaceMesh;
file "Panel_4.stl";
}
Panel_5
{
type triSurfaceMesh;
file "Panel_5.stl";
}
refinementBox
{
type searchableBox;
min ($x_negative $y_negative 0);
max ($x_positive $y_positive $z_positive);
}
};
// 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 100000;
// 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 2000000;
maxGlobalCells 4000000;
// 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;
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 "Panel_0.eMesh" "Panel_1.eMesh" "Panel_2.eMesh" "Panel_3.eMesh" "Panel_4.eMesh" "Panel_5.eMesh" ;
level 2;
}
);
// 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
{
Panel_0
{
// Surface-wise min and max refinement level
level (2 4);
// Optional specification of patch type (default is wall). No
// constraint types (cyclic, symmetry) etc. are allowed.
patchInfo
{
type wall;
inGroups (Panel_PV);
}
}
Panel_1
{
level (2 4);
patchInfo
{
type wall;
inGroups (Panel_PV);
}
}
Panel_2
{
level (2 4);
patchInfo
{
type wall;
inGroups (Panel_PV);
}
}
Panel_3
{
level (2 4);
patchInfo
{
type wall;
inGroups (Panel_PV);
}
}
Panel_4
{
level (2 4);
patchInfo
{
type wall;
inGroups (Panel_PV);
}
}
Panel_5
{
level (2 4);
patchInfo
{
type wall;
inGroups (Panel_PV);
}
}
}
}
// Resolve sharp angles
resolveFeatureAngle 30;
// resolveFeatureAngle 0;
// 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 ((1E15 2));
levels ((1E15 4));
}
}
// 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 (0.1 0.1 0.9);
// 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;
}
Surprisingly though, snappyHexMesh seems to believe that this mesh is satisfactory, as the log indicates (showing only the last iterations):
Code:
Merging all points on surface that
- are used by only two boundary faces and
- make an angle with a cosine of more than 0.707107.
Removing 2618 straight edge points ...
Edge intersection testing:
Number of edges : 22173899
Number of edges to retest : 17447
Number of intersected edges : 1085167
Undo iteration 0
----------------
Checking faces in error :
non-orthogonality > 65 degrees : 0
faces with face pyramid volume < 1e-13 : 0
faces with face-decomposition tet quality < 1e-15 : 0
faces with concavity > 80 degrees : 0
faces with skewness > 4 (internal) or 20 (boundary) : 0
faces with interpolation weights (0..1) < 0.02 : 0
faces with volume ratio of neighbour cells < 0.01 : 0
faces with face twist < 0.02 : 0
faces on cells with determinant < 0.001 : 0
Refined mesh : cells:7083129 faces:22173899 points:8009619
Cells per refinement level:
0 42210
1 42270
2 158288
3 838978
4 6001383
Writing mesh to time constant
Wrote mesh in = 245.06 s.
Mesh refined in = 2480.19 s.
Checking final mesh ...
Checking faces in error :
non-orthogonality > 65 degrees : 0
faces with face pyramid volume < 1e-13 : 0
faces with face-decomposition tet quality < 1e-15 : 0
faces with concavity > 80 degrees : 0
faces with skewness > 4 (internal) or 20 (boundary) : 0
faces with interpolation weights (0..1) < 0.02 : 0
faces with volume ratio of neighbour cells < 0.01 : 0
faces with face twist < 0.02 : 0
faces on cells with determinant < 0.001 : 0
Finished meshing without any errors
Finished meshing in = 2530.9 s.
End
Is there anything that I am missing? Which meshing parameters should I modify in order to solver this problem? Or should I change completely my approach?
Thank you a lot in advance! |
