CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Meshing & Mesh Conversion

[mesh manipulation] cfMesh + extrudeMesh -> bad quality mesh?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 20, 2018, 05:08
Exclamation cfMesh + extrudeMesh -> bad quality mesh?
  #1
New Member
 
Timo
Join Date: May 2018
Location: Delft
Posts: 8
Rep Power: 6
aerospacious is on a distinguished road
Hey fellow foamers,


The reason for this post is because I am running into some problems when Extruding a mesh generated by cfMesh.
For some reason the quality of the cfMesh is fine and the checkMesh utility does not flag a single problem.

checkMesh result cfMesh:
Code:
Mesh stats
    points:           18141991
    faces:            52760636
    internal faces:   51354113
    cells:            17311300
    faces per cell:   6.01427
    boundary patches: 7
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     17216033
    prisms:        628
    wedges:        0
    pyramids:      1190
    tet wedges:    0
    tetrahedra:    492
    polyhedra:     92957
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            6   13448
            7   14140
            8   108
            9   52169
           12   12980
           15   112

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      486      652  ok (non-closed singly connected)
                  outlet     2008     2288  ok (non-closed singly connected)
                   front   671323   675329  ok (non-closed singly connected)
                    back   684354   688365  ok (non-closed singly connected)
                     top      966     1292  ok (non-closed singly connected)
                  bottom      966     1292  ok (non-closed singly connected)
                  marlyn    46420    47106  ok (non-closed singly connected)

Checking geometry...
    Overall domain bounding box (-5.3 -0.4 -4) (10.7 -0.299998 4)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (1.74977e-18 3.67367e-13 4.64238e-17) OK.
    Max cell openness = 7.56747e-16 OK.
    Max aspect ratio = 36.5897 OK.
    Minimum face area = 7.09395e-09. Maximum face area = 0.00273625.  Face area magnitudes OK.
    Min volume = 2.33909e-12. Max volume = 0.000108415.  Total volume = 12.7988.  Cell volumes OK.
    Mesh non-orthogonality Max: 61.8058 average: 1.46265
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 1.73461 OK.
    Coupled point location match (average 0) OK.

Mesh OK.
However, when I run extrudeMesh from a patch created by cfMesh it does (not so) funny things.

checkMesh result cfMesh + extrudeMesh:
Code:
Mesh stats
    points:           1376730
    internal points:  0
    faces:            2741427
    internal faces:   1371010
    cells:            684354
    faces per cell:   6.00922
    boundary patches: 7
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     677647
    prisms:        224
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     6483
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            7   6429
            8   54

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      162      326  ok (non-closed singly connected)
                  outlet      274      550  ok (non-closed singly connected)
                   front   684354   688365  ok (non-closed singly connected)
                    back   684354   688365  ok (non-closed singly connected)
                     top      322      646  ok (non-closed singly connected)
                  bottom      322      646  ok (non-closed singly connected)
                  marlyn      629     1258  ok (non-closed singly connected)

Checking geometry...
    Overall domain bounding box (-5.3 -0.3 -4) (10.7 0.700002 4)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (-1.40344e-17 1.69986e-13 9.9365e-17) OK.
 ***High aspect ratio cells found, Max aspect ratio: 1.33419e+97, number of cells 7102
  <<Writing 7102 cells with high aspect ratio to set highAspectRatioCells
    Minimum face area = 7.3062e-09. Maximum face area = 0.0529325.  Face area magnitudes OK.
 ***Zero or negative cell volume detected.  Minimum negative volume: -1.7993e-06, Number of negative volume cells: 8
  <<Writing 8 zero volume cells to set zeroVolumeCells
    Mesh non-orthogonality Max: 162.379 average: 1.08717
   *Number of severely non-orthogonal (> 70 degrees) faces: 72.
 ***Number of non-orthogonality errors: 17.
  <<Writing 89 non-orthogonal faces to set nonOrthoFaces
 ***Error in face pyramids: 40 faces are incorrectly oriented.
  <<Writing 35 faces with incorrect orientation to set wrongOrientedFaces
 ***Max skewness = 35.2287, 3 highly skew faces detected which may impair the quality of the results
  <<Writing 3 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 5 mesh checks.

End
Oddly enough I don think I am doing something weird with the extrudeMeshDict either. Though I encountered some problems before when the merge tolerance was too low resulting in collapsed edges, this is not happening in the current situation.
Furthermore, not all meshes that I have created with cfMesh experienced these kind of problems with extrudeMesh so I am at a loss.


extrudeMeshDict:

Code:
constructFrom       patch;

sourceCase          ".";

sourcePatches       (front);
exposedPatchName    back;

flipNormals         false;

nLayers             1;

expansionRatio      1;

extrudeModel        linearNormal;

linearNormalCoeffs
{
    thickness           1;
}

mergeFaces          false;
mergeTol        1e-8;
extrudeMesh log:

Code:
Create mesh for time = 0

Selecting extrudeModel linearNormal
Extruding from patch using model linearNormal
Collapsing edges < 1e-08 of bounding box

Extruding patches 1(front) on mesh "/mnt/homedirs/timo.vanpelt/OpenFOAM/timo.vanpelt-5.0/run/cavity/with_cavity/AoA-X/AoA8_r"

Create mesh for time = 0

Adding overall 0 processor patches.
Testing:"/mnt/homedirs/timo.vanpelt/OpenFOAM/timo.vanpelt-5.0/run/cavity/with_cavity/AoA-X/AoA8_r/system/fvSchemes"
Mesh bounding box : (-5.3 -1.4 -4) (10.7 -0.4 4)
        with span : (16 1 8)
Merge distance    : 1e-08

Collapsing edges < 1e-08 ...

            Uncollapsed edges = 0 / 3368633
    Number of points : 1350658
    Not visited      : 0
    Not collapsed    : 1350658
    Collapsed        : 0

Collapsing 0 cells
Writing mesh to "/mnt/homedirs/timo.vanpelt/OpenFOAM/timo.vanpelt-5.0/run/cavity/with_cavity/AoA-X/AoA8_r/constant/region0"
End
Has anyone encountered a similar problem and found a fix, it would be greatly appreciated
aerospacious is offline   Reply With Quote

Old   July 28, 2020, 02:57
Default
  #2
New Member
 
Liz
Join Date: Apr 2020
Location: Germany
Posts: 10
Rep Power: 4
redTo is on a distinguished road
Hi Timo,

did you find out, how to improve the mesh quality with cfmesh?
redTo is offline   Reply With Quote

Reply

Tags
cfmesh, extrudemesh

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[snappyHexMesh] Bad quality mesh at external corners Bollonga OpenFOAM Meshing & Mesh Conversion 2 October 31, 2017 13:42
Gambit problems Althea FLUENT 22 January 4, 2017 03:19
von Karman effect imbalance frossi CFX 7 July 4, 2016 20:08
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 11:55
Icemcfd 11: Loss of mesh from surface mesh option? Joe CFX 2 March 26, 2007 18:10


All times are GMT -4. The time now is 18:07.