[fatemehfarshi62]

Hi every one!
Would any one please please please help me with my problem?
I have a 3d open channel. after editting the blockMesh and running check Mesh, the following error appears:
/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.2 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 2.2.2-9240f8b967db
Exec : checkMesh
Date : Jan 04 2016
Time : 11:35:20
Host : "fatemeh-Lenovo-IdeaPad-P400-Touch"
PID : 3975
Case : /home/fatemeh/Desktop/B23
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 689931
faces: 1929200
internal faces: 1790800
cells: 620000
faces per cell: 6
boundary patches: 4
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 620000
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 1000 1111 ok (non-closed singly connected)
walls 74400 75141 ok (non-closed singly connected)
outlet 1000 1111 ok (non-closed singly connected)
atmosphere 62000 62721 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (0 -5 -0.012948) (13 5 0.2)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-7.98207e-17 1.53335e-16 6.11549e-15) OK.
***High aspect ratio cells found, Max aspect ratio: 4.38289e+196, number of cells 10286
<<Writing 10286 cells with high aspect ratio to set highAspectRatioCells
Minimum face area = 1.24047e-07. Maximum face area = 0.00601414. Face area magnitudes OK.
Min volume = 2e-300. Max volume = 4.4999e-05. Total volume = 9.19087. Cell volumes OK.
Mesh non-orthogonality Max: 179.968 average: 44.4666
*Number of severely non-orthogonal (> 70 degrees) faces: 214015.
***Number of non-orthogonality errors: 31660.
<<Writing 245675 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 68843 faces are incorrectly oriented.
<<Writing 37384 faces with incorrect orientation to set wrongOrientedFaces
***Max skewness = 81.1396, 119 highly skew faces detected which may impair the quality of the results
<<Writing 119 skew faces to set skewFaces
Coupled point location match (average 0) OK.

Failed 4 mesh checks.

End


I have attached my blockMesh file in docx format. Would any one please help me with the problem? thanks a lot

[Antimony]

Hi,

I took a quick look at your case and ran checkMesh with the -allGeometry and -allTopology tags. It stated that there were cells with negative volumes (check images).

This usually happens when your block is incorrectly defined - up to version 3, OF is very sensitive to the order of your vertices for the blocks. So you might want to double check that.

Also, I noticed some vertex components like 0.149004 and 0.15. If they are meant to be the same, you might want to put the same value, 0.15 I guess. The small gap between the components may also be causing trouble.

Hope this helps.

Cheers,
Antimony

[fatemehfarshi62]

Hi and thanks a lot for your attention and kindness.
In fact, this is a part of of an open channel which the difference between their z coordinates, makes the longitudinal slope of the channel.
I have checked the blocks several times and didn't find the error.
Would you please tell me which is the best:1-deleting the bad form cells?
2- using gambit for meshing and export it to openfoam?
Thanks a lot and best wishes.

[Antimony]

Hi,

You are welcome.

I wouldn't recommend deleting off the problem cells. You might end up with a mesh that does not correspond to the geometry you are trying to model. Just as a test, I deleted off the problem cells and the checkMeshLog doesn't look any better than before.

You might want to give it a shot with a different mesher perhaps.

Cheers,
Antimony

[fatemehfarshi62]

Hi! I am really thankful for what you have done. Ok thanks I will try gambit for meshing. Thanks again and again and best regards