Problems after checkMesh - how to solve?

sErik · December 10, 2009, 09:58

Hello Foamers,

I converted a CCM+ mesh and when executing checkMesh, I get this here

Quote:

Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 5903490
faces: 18097669
internal faces: 17751411
cells: 6080579
boundary patches: 26
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 4156114
prisms: 1363842
wedges: 25186
pyramids: 804
tet wedges: 2597
tetrahedra: 40354
polyhedra: 491682

Checking topology...
Boundary definition OK.
Point usage OK.
<<Found 2017 neighbouring cells with multiple inbetween faces.
Upper triangular ordering OK.
<<Writing 4158 unordered faces to set upperTriangularFace
Face vertices OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface topology
Eintritt 1761 1810 ok (non-closed singly connected)
Austritt 3036 3123 ok (non-closed singly connected)
Leitung_11 28081 24960 ok (non-closed singly connected)
Leitung_12 21473 18842 ok (non-closed singly connected)
Leitung_13 14308 12186 ok (non-closed singly connected)
Leitung_14 5708 5466 ok (non-closed singly connected)
Verbindungsstueck_1118000 17020 ok (non-closed singly connected)
Verbindungsstueck_126717 7114 ok (non-closed singly connected)
Leitung_21 80466 79460 ok (non-closed singly connected)
Leitung_22 10151 8964 ok (non-closed singly connected)
Leitung_23 12323 10660 ok (non-closed singly connected)
Leitung_24 8416 7417 ok (non-closed singly connected)
Leitung_25 5990 5338 ok (non-closed singly connected)
Leitung_26 3246 3401 ok (non-closed singly connected)
Leitung_27 3577 3798 ok (non-closed singly connected)
Verbindungsstueck_2116172 15818 ok (non-closed singly connected)
Verbindungsstueck_225001 5292 ok (non-closed singly connected)
Leitung_31 20370 19995 ok (non-closed singly connected)
Leitung_32 12077 10798 ok (non-closed singly connected)
Leitung_33 10606 9735 ok (non-closed singly connected)
Leitung_34 8388 7562 ok (non-closed singly connected)
Verbindungsstueck_3117792 16749 ok (non-closed singly connected)
Verbindungsstueck_326627 6846 ok (non-closed singly connected)
Kasten_11 20922 20131 ok (non-closed singly connected)
Kasten_12 4825 4962 ok (non-closed singly connected)
Gap_Closure_Faces 225 253 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-0.440582 0.141056 -0.0649491) (2.36066 0.445929 0.205401)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (1.2453e-17 -2.63112e-17 -3.40415e-17) OK.
***High aspect ratio cells found, Max aspect ratio: 6.62921e+292, number of cells 24
<<Writing 24 cells with high aspect ratio to set highAspectRatioCells
Minumum face area = 5.83095e-13. Maximum face area = 2.35623e-05. Face area magnitudes OK.
Min volume = 1.66667e-300. Max volume = 8.49121e-08. Total volume = 0.00250369. Cell volumes OK.
Mesh non-orthogonality Max: 153.681 average: 13.0845
*Number of severely non-orthogonal faces: 36885.
***Number of non-orthogonality errors: 127.
<<Writing 37012 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 290 faces are incorrectly oriented.
<<Writing 249 faces with incorrect orientation to set wrongOrientedFaces
#0 Foam::error:

rintStack(Foam::Ostream&) in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#1 Foam::sigFpe::sigFpeHandler(int) in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#2 ?? in "/lib/libc.so.6"
#3 Foam:

rimitiveMesh::checkFaceSkewness(bool, Foam::HashSet<int, Foam::Hash<int> >*) const in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#4 Foam::checkGeometry(Foam:

olyMesh const&, bool) in "/opt/OpenFOAM/OpenFOAM-1.6/applications/bin/linux64GccDPOpt/checkMesh"
#5 main in "/opt/OpenFOAM/OpenFOAM-1.6/applications/bin/linux64GccDPOpt/checkMesh"
#6 __libc_start_main in "/lib/libc.so.6"
#7 _start at /usr/src/packages/BUILD/glibc-2.9/csu/../sysdeps/x86_64/elf/start.S:116
Gleitkomma-Ausnahme

Any ideas, how to solve this problem?
First I tried to delete the broken faces, but there I also have some problems (take a look: http://www.cfd-online.com/Forums/ope...ing-cells.html )

Best regards!

sErik · December 14, 2009, 04:28

Doesn't anyone have an idea?
Is it possible, that there are porblems with hanging vertices? There is a mix of polyhedral and tetrahedral cells in the original CCM file.

sErik · December 14, 2009, 09:49

Now I remeshed the original CCM+ file, so that there were only tetrahedrons, and then executed ccm26ToFoam without any problems. But with checkMesh, I get this again:

Quote:

Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 4117194
faces: 25971655
internal faces: 25514953
cells: 11248772
boundary patches: 26
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 0
prisms: 6440594
wedges: 669
pyramids: 8892
tet wedges: 692
tetrahedra: 4790830
polyhedra: 7095

Checking topology...
Boundary definition OK.
Point usage OK.
<<Found 16 neighbouring cells with multiple inbetween faces.
Upper triangular ordering OK.
<<Writing 32 unordered faces to set upperTriangularFace
Face vertices OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface topology
Eintritt 2056 1709 ok (non-closed singly connected)
Austritt 2399 1992 ok (non-closed singly connected)
Leitung_11 42976 21881 ok (non-closed singly connected)
Leitung_12 30138 15203 ok (non-closed singly connected)
Leitung_13 20433 10340 ok (non-closed singly connected)
Leitung_14 9016 4779 ok (non-closed singly connected)
Verbindungsstueck_1119763 10537 ok (non-closed singly connected)
Verbindungsstueck_127305 4022 ok (non-closed singly connected)
Leitung_21 134484 68478 ok (non-closed singly connected)
Leitung_22 10386 5299 ok (non-closed singly connected)
Leitung_23 13568 6898 ok (non-closed singly connected)
Leitung_24 9042 4637 ok (non-closed singly connected)
Leitung_25 6512 3364 ok (non-closed singly connected)
Leitung_26 2250 1378 ok (non-closed singly connected)
Leitung_27 3419 2011 ok (non-closed singly connected)
Verbindungsstueck_2115346 8196 ok (non-closed singly connected)
Verbindungsstueck_225676 3101 ok (non-closed singly connected)
Leitung_31 27488 14439 ok (non-closed singly connected)
Leitung_32 16428 8361 ok (non-closed singly connected)
Leitung_33 14876 7562 ok (non-closed singly connected)
Leitung_34 11499 5884 ok (non-closed singly connected)
Verbindungsstueck_3117209 9125 ok (non-closed singly connected)
Verbindungsstueck_322515 1470 ok (non-closed singly connected)
Kasten_11 25917 13407 ok (non-closed singly connected)
Kasten_12 5864 3190 ok (non-closed singly connected)
Gap_Closure_Faces 137 90 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-0.440584 0.141049 -0.0649587) (2.36067 0.445945 0.20541)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-7.41015e-17 2.41612e-16 2.23077e-17) OK.
***High aspect ratio cells found, Max aspect ratio: 1.07065e+294, number of cells 21543
<<Writing 21543 cells with high aspect ratio to set highAspectRatioCells
***Zero or negative face area detected. Minimum area: 0
<<Writing 8270 zero area faces to set zeroAreaFaces
Min volume = 1.66667e-300. Max volume = 7.76812e-07. Total volume = 0.00257272. Cell volumes OK.
Mesh non-orthogonality Max: 180 average: 23.132
*Number of severely non-orthogonal faces: 765830.
***Number of non-orthogonality errors: 37206.
<<Writing 803036 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 9428 faces are incorrectly oriented.
<<Writing 8784 faces with incorrect orientation to set wrongOrientedFaces
Gleitkomma-Ausnahme

I had to rename all the boundarys after running ccm26ToFoam, because they were like 12_abcdefg-34. To be able to perform checkMesh, I changed all the names into a form like abcdefg34. Could this be the problem?

I really appreciate some help.

madad2005 · December 15, 2009, 05:55

I think your original CCM mesh is the problem. Have you set your quality criteria properly? Did you make sure the CCM mesh had no negative volumes or skewness issues before writing it out? I suggest you zoom into any low quality areas and see what the cells look like there. You may need to do some resourcing to try and resolve them.

Renaming the zones in the boundary file shouldn't give you this problem.

sErik · December 15, 2009, 08:21

Hi madad,
thank you for your answer.
Meanwhile, I had the same thought. I think that there could be some problems with the internal faces in my original CCM mesh. I'll see what I can do about it.
The point that's confusing my is/was, that I had no porblems converting the file with ccm26ToFoam.

madad2005 · December 15, 2009, 08:59

The converter is just taking the information from one side and converting it to another. It isn't interested in whether the mesh tiself is valid. I've had these types of issues with meshes in the past after conversion, to find out I had inside-out cells in the original mesh!

sErik · December 16, 2009, 05:58

You were right, I remeshed the CCM file with a coarser grid and now checkMesh is fine.

Nevertheless I'll have to take a closer look at the mesh later on, because I actually need it with the original size.

kdneroorkar · February 29, 2012, 15:21

Hi, were you able to figure out what the issue was in the ccm mesh that was causing the error?

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December 14, 2009, 04:28		#2
sErik Member Join Date: Nov 2009 Location: Munich Posts: 43 Rep Power: 17	Doesn't anyone have an idea? Is it possible, that there are porblems with hanging vertices? There is a mix of polyhedral and tetrahedral cells in the original CCM file. scapp likes this.

December 15, 2009, 05:55		#4
madad2005 Senior Member Anonymous Join Date: Mar 2009 Posts: 110 Rep Power: 17	I think your original CCM mesh is the problem. Have you set your quality criteria properly? Did you make sure the CCM mesh had no negative volumes or skewness issues before writing it out? I suggest you zoom into any low quality areas and see what the cells look like there. You may need to do some resourcing to try and resolve them. Renaming the zones in the boundary file shouldn't give you this problem.

December 15, 2009, 08:21		#5
sErik Member Join Date: Nov 2009 Location: Munich Posts: 43 Rep Power: 17	Hi madad, thank you for your answer. Meanwhile, I had the same thought. I think that there could be some problems with the internal faces in my original CCM mesh. I'll see what I can do about it. The point that's confusing my is/was, that I had no porblems converting the file with ccm26ToFoam.

December 15, 2009, 08:59		#6
madad2005 Senior Member Anonymous Join Date: Mar 2009 Posts: 110 Rep Power: 17	The converter is just taking the information from one side and converting it to another. It isn't interested in whether the mesh tiself is valid. I've had these types of issues with meshes in the past after conversion, to find out I had inside-out cells in the original mesh!

December 16, 2009, 05:58		#7
sErik Member Join Date: Nov 2009 Location: Munich Posts: 43 Rep Power: 17	You were right, I remeshed the CCM file with a coarser grid and now checkMesh is fine. Nevertheless I'll have to take a closer look at the mesh later on, because I actually need it with the original size.

February 29, 2012, 15:21		#8
kdneroorkar Member kshitij neroorkar Join Date: Mar 2009 Location: Michigan, USA Posts: 32 Rep Power: 17	Hi, were you able to figure out what the issue was in the ccm mesh that was causing the error?