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[mesh manipulation] Mesh Problems after extrudeMesh

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Old   June 16, 2015, 19:23
Default Mesh Problems after extrudeMesh
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Cristina Moreira
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Greetings,

i want to refine a contour of a structure inside a simple box created using blockMesh.

Using Salome, i created the .stl file needed and used Helyx to confirm that everyting was ok.

Also, using cellSet i created a zone neer the contour in order to obtain a better refinement.

Everything was ok. Only a problem appeared do to fact that i was creating a 3D mesh that in reality was 2D (Ny=1 and ymax=0.01) with blockMeshDict.

I was expecting to solve this problem with extrudeMesh but something went wrong.

The commands used are:

blockMesh
setSet -batch setRefin
refineMesh -dict system -overwrite
surfaceFeatureExtract (with 180)
snappyHexMesh -overwrite

---- till now the only problem was only the 3D that need to be 2D ----

So i run extrudeMesh (as i have done in previously cases) but the mesh appeared with several errors. (see images)

extrudeMeshDict:

Code:
// What to extrude:
//      patch   : from patch of another case ('sourceCase')

constructFrom patch;
sourceCase ;
sourcePatches (empty1);

// If construct from patch: patch to use for back (can be same as sourcePatch)
exposedPatchName empty1;

// Flip surface normals before usage.
flipNormals false;

//- Linear extrusion in point-normal direction
extrudeModel        linearNormal;

nLayers             1;

expansionRatio      1.0;

linearNormalCoeffs
{
    thickness       0.01;
}

// Do front and back need to be merged? Usually only makes sense for 360
// degree wedges.
mergeFaces false;
Can anyone give me a tip on how to solve this problem?

Error message:
Code:
 cd 15
cristina@cristina-HP-Pavilion-g6-Notebook-PC:~/OpenFOAM/cristina-2.2.2/run/test/15$ checkMesh
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  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   : Jun 17 2015
Time   : 11:20:00
Host   : "cristina-HP-Pavilion-g6-Notebook-PC"
PID    : 5172
Case   : /home/cristina/OpenFOAM/cristina-2.2.2/run/test/15
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:           1693614
    internal points:  0
    faces:            3359069
    internal faces:   1671689
    cells:            837421
    faces per cell:   6.00744
    boundary patches: 7
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     831276
    prisms:        186
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     5959
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            7   5501
            8   457
            9   1

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      200      402  ok (non-closed singly connected)
                  outlet      400      802  ok (non-closed singly connected)
                  bottom     2617     5238  ok (non-closed singly connected)
                  empty1  1674842  1693614  ok (non-closed singly connected)
                  empty2        0        0                        ok (empty)
              atmosphere     2710     5422  ok (non-closed singly connected)
              ramp_solid     6611    13224  ok (non-closed singly connected)

Checking geometry...
    Overall domain bounding box (0 -0.01 -6.96284e-27) (13.95 0.000535259 1)
    Mesh (non-empty, non-wedge) directions (0 0 0)
    Mesh (non-empty) directions (0 0 0)
 ***Number of edges not aligned with or perpendicular to non-empty directions: 20428
  <<Writing 26756 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (2.52486e-18 8.58837e-12 1.05755e-16) OK.
    Max cell openness = 2.15239e-16 OK.
    Max aspect ratio = -1 OK.
    Minimum face area = 4.38e-08. Maximum face area = 6.98e-05.  Face area magnitudes OK.
    Min volume = 2.02056e-10. Max volume = 3.49e-07.  Total volume = 0.138252.  Cell volumes OK.
    Mesh non-orthogonality Max: 143.36 average: 1.80463
   *Number of severely non-orthogonal (> 70 degrees) faces: 69.
 ***Number of non-orthogonality errors: 36.
  <<Writing 105 non-orthogonal faces to set nonOrthoFaces
 ***Error in face pyramids: 208 faces are incorrectly oriented.
  <<Writing 172 faces with incorrect orientation to set wrongOrientedFaces
 ***Max skewness = 9.84588, 1 highly skew faces detected which may impair the quality of the results
  <<Writing 1 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 4 mesh checks.

End
Best regards

Cristina
Attached Images
File Type: jpg beforeExtrude.jpg (28.9 KB, 89 views)
File Type: jpg afterExtrude.jpg (36.9 KB, 78 views)

Last edited by CrisMoreira; June 17, 2015 at 06:21.
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Old   July 4, 2015, 18:37
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Daniel P. Combest
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Cristina,

If possible, you may want to post an example case to make the process of getting an answer more efficient. If possible, share a link to the unmeshed case with instruction on what you are doing (similar to your first post) and then I will take a look.

Best Regards,

Dan
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Old   July 4, 2015, 18:51
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Cristina Moreira
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Hi Dan,
Thank you for your answer but the problem is solved.
The problem was on my .stl that had an "occult" face by mistake.
Thank you anyway.
Cristina
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Old   July 4, 2015, 22:52
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Daniel P. Combest
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Excellent! Glad you figured it out and thanks for the update.
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Old   October 2, 2016, 23:49
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Quote:
Originally Posted by CrisMoreira View Post
Hi Dan,
Thank you for your answer but the problem is solved.
The problem was on my .stl that had an "occult" face by mistake.
Thank you anyway.
Cristina
What is an "occult" face?
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