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No layers in a small gap

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Old   December 21, 2011, 05:18
Default No layers in a small gap
  #1
New Member
 
Stefan
Join Date: Nov 2011
Posts: 4
Rep Power: 5
bobburnquist is on a distinguished road
Hi,

i want to mesh a small gap (i hope its the correct word for it) with snappyHM and create layers. This wont work, and i dont know why.

As u can see in the picture, there is just one refinment level.

In my SHM-dict,i changed these values again and again:
PHP Code:
layers
    
{
       
        
motorBike_patch0
        
{
            
nSurfaceLayers 2;
        }    }
    
    
// Expansion factor for layer mesh
    
expansionRatio 1.1;//1.3
    //- 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;//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 0.1//0.1
    //- 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.
    
nGrow 1;

    
// Advanced settings
    //- When not to extrude surface. 0 is flat surface, 90 is when two faces
    //  make straight angle.
    
featureAngle 30;
    
//- Maximum number of snapping relaxation iterations. Should stop
    //  before upon reaching a correct mesh.
    
nRelaxIter 3
My log.file:
PHP Code:
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //




Patch    Region
-----    ------
motorBike:
5    motorBike_patch0
Added patches in 
0 s
Selecting decompositionMethod hierarchical
Refinement phase
----------------
Found point (0.01 0 0in cell 44850 on processor 0
Reading external feature lines
.
Read feature lines in 0.06 s
.............................



Shell refinement iteration 1
----------------------------
Marked for refinement due to refinement shells    0 cells.
Determined cells to refine in 1.71 s
Selected 
for internal refinement 0 cells (out of 1684138)
Stopping refining since too few cells selected.

Splitting mesh at surface intersections
---------------------------------------
Introducing baffles for 644084 faces that are intersected by the surface.
Edge intersection testing:
    
Number of edges             6307648
    Number of edges to retest   
5141672
    Number of intersected edges 
1284130
Created baffles in 
13.14 s

After introducing baffles 
cells:1684138  faces:6307648  points:2302709
Cells per refinement level
:
    
0    0
    1    80000
    2    1604138
Introducing baffles to block off problem cells
----------------------------------------------
markFacesOnProblemCells marked 1920631 additional internal faces to be converted into baffles.
Analyzed problem cells in 5.33 s

Introducing baffles to delete problem cells
.
Edge intersection testing:
    
Number of edges             8228279
    Number of edges to retest   
5781742
    Number of intersected edges 
1284135
Created baffles in 
27.79 s

After introducing baffles 
cells:1684138  faces:8228279  points:2302709
Cells per refinement level
:
    
0    0
    1    80000
    2    1604138
Remove unreachable sections of mesh
-----------------------------------
Keeping all cells in region 10088 containing point (0.01 0 0)
Selected for keeping 720000 cells.
Edge intersection testing:
    
Number of edges             2445000
    Number of edges to retest   
0
    Number of intersected edges 
320000
Split mesh in 
4.13 s

After subsetting 
cells:720000  faces:2445000  points:1006507
Cells per refinement level
:
    
0    0
    1    80000
    2    640000
Handling cells with snap problems
---------------------------------
Introducing baffles for 320000 faces that are intersected by the surface.
Edge intersection testing:
    
Number of edges             2445000
    Number of edges to retest   
1282000
    Number of intersected edges 
320000
Created baffles in 
2.63 s

After introducing baffles 
cells:720000  faces:2445000  points:1006507
Cells per refinement level
:
    
0    0
    1    80000
    2    640000
Introducing baffles to block off problem cells
----------------------------------------------
markFacesOnProblemCells marked 0 additional internal faces to be converted into baffles.
Analyzed problem cells in 1.76 s

Introducing baffles to delete problem cells
.
Edge intersection testing:
    
Number of edges             2445000
    Number of edges to retest   
0
    Number of intersected edges 
320000
Created baffles in 
1.71 s

After introducing baffles 
cells:720000  faces:2445000  points:1006507
Cells per refinement level
:
    
0    0
    1    80000
    2    640000
Remove unreachable sections of mesh
-----------------------------------
Keeping all cells in region 0 containing point (0.01 0 0)
Selected for keeping 720000 cells.
Edge intersection testing:
    
Number of edges             2445000
    Number of edges to retest   
0
    Number of intersected edges 
320000
Split mesh in 
1.88 s

After subsetting 
cells:720000  faces:2445000  points:1006507
Cells per refinement level
:
    
0    0
    1    80000
    2    640000
dupNonManifoldPoints 
Found 0 non-manifold points (out of 1006507)
Edge intersection testing:
    
Number of edges             2445000
    Number of edges to retest   
0
    Number of intersected edges 
320000
getDuplicateFaces 
found 0 pairs of duplicate faces.
Detected unsplittable baffles 0
Merge refined boundary faces
----------------------------
mergePatchFaces Merging 0 sets of faces.
Removing 0 straight edge points.
Refined mesh cells:720000  faces:2445000  points:1006507
Cells per refinement level
:
    
0    0
    1    80000
    2    640000
Writing mesh to time constant
Written mesh in 
19.77 s.
Morphing phase
--------------
Constructing mesh displacer ...
Using mesh parameters 
{
    
maxNonOrtho     65;
    
maxBoundarySkewness 20;
    
maxInternalSkewness 4;
    
maxConcave      80;
    
minFlatness     0.5;
    
minVol          1e-13;
    
minArea         -1;
    
minTwist        0.02;
    
minDeterminant  0.001;
    
minFaceWeight   0.02;
    
minVolRatio     0.01;
    
minTriangleTwist -1;
    
nSmoothScale    4;
    
errorReduction  0.75;
}

Checking initial mesh ...
Checking faces in error :
    
non-orthogonality >  65 degrees                        0
    faces with face pyramid volume 
1e-13                 2244000
    faces with concavity 
>  80 degrees                     0
    faces with skewness 
>   (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
Detected 2244000 illegal faces 
(concavezero area or negative cell pyramid volume)
Checked initial mesh in 4.67 s

Smoothing patch points 
...
Smoothing iteration 0
Found 0 non
-mainfold point(s).
Scaling iteration 0
Moving mesh using diplacement scaling 
min:1  max:1
Checking faces in error 
:
    
non-orthogonality >  65 degrees                        0
    faces with face pyramid volume 
1e-13                 2244000
    faces with concavity 
>  80 degrees                     0
    faces with skewness 
>   (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
Successfully moved mesh
Smoothing iteration 1
Found 0 non
-mainfold point(s).
Scaling iteration 0
Moving mesh using diplacement scaling 
min:1  max:1
Checking faces in error 
:
    
non-orthogonality >  65 degrees                        0
    faces with face pyramid volume 
1e-13                 2244000
    faces with concavity 
>  80 degrees                     0
    faces with skewness 
>   (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
Successfully moved mesh
Smoothing iteration 2
Found 0 non
-mainfold point(s).
Scaling iteration 0
Moving mesh using diplacement scaling 
min:1  max:1
Checking faces in error 
:
    
non-orthogonality >  65 degrees                        0
    faces with face pyramid volume 
1e-13                 2244000
    faces with concavity 
>  80 degrees                     0
    faces with skewness 
>   (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
Successfully moved mesh
Patch points smoothed in 
13.19 s

Calculating patchDisplacement 
as distance to nearest surface point ...
Wanted displacement average:1.60516e-05 min:5.95374e-06 max:1.6127e-05
Calculated surface displacement in 
0.11 s

Smoothing displacement 
...
Iteration 0
Iteration 10
Iteration 20
Displacement smoothed in 
1.73 s

Moving mesh 
...
Iteration 0
Moving mesh using diplacement scaling 
min:1  max:1
Checking faces in error 
:
    
non-orthogonality >  65 degrees                        0
    faces with face pyramid volume 
1e-13                 2244000
    faces with concavity 
>  80 degrees                     0
    faces with skewness 
>   (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
Successfully moved mesh
Moved mesh in 
4.05 s

Repatching faces according to nearest surface 
...
Repatched 0 faces in 1.66 s

Edge intersection testing
:
    
Number of edges             2445000
    Number of edges to retest   
1308916
    Number of intersected edges 
320000
Snapped mesh 
cells:720000  faces:2445000  points:1006507
Cells per refinement level
:
    
0    0
    1    80000
    2    640000
Writing mesh to time constant
Written mesh in 
17.19 s.
Shrinking and layer addition phase
----------------------------------
Using mesh parameters 
{
    
maxNonOrtho     65;
    
maxBoundarySkewness 20;
    
maxInternalSkewness 4;
    
maxConcave      80;
    
minFlatness     0.5;
    
minVol          1e-13;
    
minArea         -1;
    
minTwist        0.02;
    
minDeterminant  0.001;
    
minFaceWeight   0.02;
    
minVolRatio     0.01;
    
minTriangleTwist -1;
    
nSmoothScale    4;
    
errorReduction  0.75;
}
Merging all faces of a cell
---------------------------
    - 
which are on the same patch
    
which make an angle 30 degrees
      
(cos:0.866025)
    - as 
long as the resulting face doesn't become concave by more than 90 degrees
      (0=straight, 180=fully concave)
Merging 0 sets of faces.
No faces merged ...
Merging all points on surface that
- are used by only two boundary faces and
- make an angle with a cosine of more than 0.866025.
No straight edges simplified and no points removed ...
Constructing mesh displacer ...
Checking mesh manifoldness ...
Checking initial mesh ...
Checking faces in error :
    non-orthogonality >  65 degrees                        : 0
    faces with face pyramid volume < 1e-13                 : 2244000
    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
Detected 2244000 illegal faces (concave, zero area or negative cell pyramid volume)
Handling points with inconsistent layer specification ...
Handling non-manifold points ...
Checking patch manifoldness ...
Outside of local patch is multiply connected across edges or points at 0 points.
Set displacement to zero for all 0 non-manifold points
Handling feature edges ...
Set displacement to zero for points on 0 feature edges
Handling cells with warped patch faces ...
Set displacement to zero on 0 warped faces since layer would be > 0.5 of the size of the bounding box.
Growing non-extrusion points by one layer ...
Set displacement to zero for an additional 0 points.
patch               faces    layers avg thickness[m]
                                    near-wall overall
-----               -----    ------ --------- -------
motorBike_patch0    320000   2      1.36e-12  2.86e-12
medialAxisSmoothingInfo : Calculate distance to Medial Axis ...
shrinkMeshDistance : Smoothing normals ...
    Iteration 0   residual 1.64e-18
Inserting points on patch ski
Inserting points on patch snow
Inserting points on patch sides
Inserting points on patch inlet
Inserting points on patch outlet
shrinkMeshDistance : Smoothing normals ...
shrinkMeshDistance : Smoothing normals in interior ...
    Iteration 0   residual 0.0273
Layer addition iteration 0
--------------------------
Prevented extrusion on 0 coupled patch points during syncPatchDisplacement.
Determining displacement for added points according to pointNormal ...
Prevented extrusion on 0 coupled patch points during syncPatchDisplacement.
shrinkMeshMedialDistance : Smoothing using Medial Axis ...
shrinkMeshMedialDistance : Reduce layer thickness at 4000 nodes where thickness to medial axis distance is large 
shrinkMeshDistance : Removing isolated regions ...
Number isolated points extrusion stopped : 0
shrinkMeshDistance : Smoothing field ...
    Iteration 0   residual 2.44e-15
shrinkMeshMedialDistance : Moving mesh ...
Iteration 0
Moving mesh using diplacement scaling : min:1  max:1
Checking faces in error :
    non-orthogonality > 65  degrees                        : 0
    faces with face pyramid volume < 1e-13                 : 2244000
    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
shrinkMeshMedialDistance : Successfully moved mesh
shrinkMeshMedialDistance : Finished moving mesh ...
Prevented extrusion on 0 coupled patch points during syncPatchDisplacement.
truncateDisplacement : Unextruded 0 faces due to non-consecutive vertices being extruded.
Setting up information for layer truncation ...
Checking mesh with layer ...
Checking faces in error :
    non-orthogonality > 65  degrees                        : 0
    faces with face pyramid volume < 1e-13                 : 4152016
    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
Detected 4152016 illegal faces (concave, zero area or negative cell pyramid volume)
Extruding 0 out of 320000 faces. Removed extrusion at 180000 faces.

Layer addition iteration 1
--------------------------
Prevented extrusion on 0 coupled patch points during syncPatchDisplacement.
Determining displacement for added points according to pointNormal ...
Prevented extrusion on 0 coupled patch points during syncPatchDisplacement.
shrinkMeshMedialDistance : Smoothing using Medial Axis ...
shrinkMeshMedialDistance : Reduce layer thickness at 0 nodes where thickness to medial axis distance is large 
shrinkMeshDistance : Removing isolated regions ...
Number isolated points extrusion stopped : 0
shrinkMeshDistance : Smoothing field ...
    Iteration 0   residual 0
shrinkMeshMedialDistance : Moving mesh ...
Iteration 0
Moving mesh using diplacement scaling : min:1  max:1
Checking faces in error :
    non-orthogonality > 65  degrees                        : 0
    faces with face pyramid volume < 1e-13                 : 2244000
    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
shrinkMeshMedialDistance : Successfully moved mesh
shrinkMeshMedialDistance : Finished moving mesh ...
Prevented extrusion on 0 coupled patch points during syncPatchDisplacement.
truncateDisplacement : Unextruded 0 faces due to non-consecutive vertices being extruded.
Setting up information for layer truncation ...
Checking mesh with layer ...
Checking faces in error :
    non-orthogonality > 65  degrees                        : 0
    faces with face pyramid volume < 1e-13                 : 2244000
    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
Detected 2244000 illegal faces (concave, zero area or negative cell pyramid volume)
Extruding 0 out of 320000 faces. Removed extrusion at 0 faces.
Edge intersection testing:
    Number of edges             : 2445000
    Number of edges to retest   : 0
    Number of intersected edges : 320000
Writing 0 added cells to cellSet addedCells
Writing 0 faces inside added layer to faceSet layerFaces
Layer mesh : cells:720000  faces:2445000  points:1006507
Cells per refinement level:
    0    0
    1    80000
    2    640000
Writing mesh to time constant
Written mesh in = 62.4 s.
Finished meshing in = 279 s.
End 
Two Problems are possible:
1) The meshing is not possible because of the 1mm.
2) My block Mesh box is too big.

Maybe you have an idea, 4 weeks remain for my thesis

Edit: Sry for the bad picture quality. You can read, stl stl and 1 mm , maybe.
Attached Images
File Type: jpg bl1.jpg (27.6 KB, 140 views)
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Old   July 2, 2012, 10:28
Default
  #2
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Join Date: Apr 2010
Posts: 53
Rep Power: 7
bephi is on a distinguished road
Hi!
Have you figured out what causes the "faces with face pyramid volume < 1e-13" error. In my case all other criteria are also fine except a large number of these pyramid volumes...

Has someone experienced the same problems?
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Old   November 25, 2012, 09:54
Default The same problem
  #3
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Hossein Yahyazadeh
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Hi,
I have the same problem as bobburnquist. I am using snappyHexMesh in interFoam, I really need help
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Old   August 24, 2015, 04:29
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hello,

has anyone figured out which parameters could be tweaked to help reduce the high number of faces with face pyramid volumes < 1e-13 ?
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Old   August 24, 2015, 09:19
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if ever, as trivial as it may seem, my problem came from the large number of blocks "divisions" i set in the blockMeshDict file (and not from the snappyHexMeshDict);
i reduced them from (50 50 50) to (10 10 40) my geometry being a thin (x,y) and long (z) vertical cylinder

so im guessing as a consequence of high divisions ->small cells with face pyramids volumes <1e-13
(also this threshold is set in snappyHexMeshDict in meshqualitycontrols, minVol 1e-13; )
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Old   August 25, 2015, 14:58
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DanielP
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Hello bobburnquist,

Can you please send me the stl file with the parameters you wish to mesh ?
I will try it to mesh it with snappy. Also, what kind of problem are you trying to solve (compressible, incompressible, combustion, etc) ?

Daniel
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Old   August 26, 2015, 09:38
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hello daniel,

i'm afraid you might be a few years too late to help out bobburnquist :s


best,
a.
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