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

[mesh manipulation] TranformPoints gives skewed mesh Possible Bug

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 19, 2008, 23:48
Default TranformPoints gives skewed mesh Possible Bug
  #1
Member
 
Andrew King
Join Date: Mar 2009
Location: Perth, Western Australia, Australia
Posts: 82
Rep Power: 17
andersking is on a distinguished road
Description:
I am trying to build a mesh by flipping and combining a submesh. To construct the mesh I would like to flip the original mesh and merge the original and the flipped mesh together.

ie. if the original mesh is called "left" then the process is roughly

cp -rv left right
transformPoints . right -scale "(-1 1 1)"
(or alternatively transformPoints . right -rotate "((1 1 1) (-1 1 1))" - it doesn't matter which one as both fail"
mergeMesh . left . right

the transformPoints step always results in a bad mesh (according to checkmesh).


Solver/Application:
transformPoints
or checkMesh

Source file:King

Testcase:


Platform:
linux32 (but most likely non-specific)

Version:
OpenFOAM-1.4.1 (extend)

Notes:
I have attached a test case that illustrates the problem.
taking the case and running blockMesh and checkMesh gives:


Checking topology...
Boundary definition OK.
Point usage OK.
Upper triangular ordering OK.
Topological cell zip-up check OK.
Face vertices OK.
Face-face connectivity OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface
defaultFaces 600 602 ok (closed singly connected surface)

Checking geometry...
Boundary openness (3.41901e-17 3.41901e-17 -1.37863e-18) OK.
This mesh has no valid solving directions. dirs = (-1 -1 -1). Please check mesh definition for empty patches.
This is a 0-D mesh
Domain bounding box: (0 0 0) (0.001 0.001 0.001)
Max cell openness = 1.65436e-16 OK.
Max aspect ratio = 1 OK.
Minumum face area = 1e-08. Maximum face area = 1e-08. Face area magnitudes OK.
Min volume = 1e-12. Max volume = 1e-12. Total volume = 1e-09. Cell volumes OK.
Mesh non-orthogonality Max: 8.53774e-07 average: 0
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 6.50521e-15 OK.
Min/max edge length = 0.0001 0.0001 OK.
All angles in faces OK.
Face flatness (1 = flat, 0 = butterfly) : average = 1 min = 1
All face flatness OK.

Failed 1 mesh checks.

End

then after running transformPoints . block -scale "(-1 1 1)" checkMesh gives


Checking topology...
Boundary definition OK.
Point usage OK.
Upper triangular ordering OK.
Topological cell zip-up check OK.
Face vertices OK.
Face-face connectivity OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface
defaultFaces 600 602 ok (closed singly connected surface)

Checking geometry...
Boundary openness (3.41901e-17 -3.41901e-17 1.37863e-18) OK.
This mesh has no valid solving directions. dirs = (-1 -1 -1). Please check mesh definition for empty patches.
This is a 0-D mesh
Domain bounding box: (-0.001 0 0) (0 0.001 0.001)
***High aspect ratio cells found, Max aspect ratio: 6.29961e+191, number of cells 1000

<<Writing 1000 cells with high aspect ratio to set highAspectRatioCells
Minumum face area = 1e-08. Maximum face area = 1e-08. Face area magnitudes OK.
Min volume = 2e-300. Max volume = 2e-300. Total volume = 2e-297. Cell volumes OK.
Mesh non-orthogonality Max: 180 average: 180
<font color="ff0000"> ***Number of non-orthogonality errors: 2700.

<<Writing 2700 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 6000 faces are incorrectly oriented.
<<Writing 3300 faces with incorrect orientation to set wrongOrientedFaces
Max skewness = 5.42101e-15 OK.
Min/max edge length = 0.0001 0.0001 OK.
All angles in faces OK.
Face flatness (1 = flat, 0 = butterfly) : average = 1 min = 1
All face flatness OK.

Failed 4 mesh checks.

End</font>

Am I missing a stage or option to do this conversion? or is this a bug in transformPoints (or checkMesh)?

cheers,
Andrew

block.tgz
__________________
Dr Andrew King
Fluid Dynamics Research Group
Curtin University
andersking is offline   Reply With Quote

Old   March 20, 2008, 08:00
Default The calculation of the transfo
  #2
Senior Member
 
Mattijs Janssens
Join Date: Mar 2009
Posts: 1,419
Rep Power: 26
mattijs is on a distinguished road
The calculation of the transformation tensor breaks down (no clearly defined path to rotate over 180 degrees). Use two steps:

// Rotate 90 degrees around z-axis
transformPoints .. block -rotate '((1 0 0)(0 1 0))'
// Rotate 90 degrees around z-axis
transformPoints .. block -rotate '((1 0 0)(0 1 0))'
mattijs is offline   Reply With Quote

Old   March 20, 2008, 10:32
Default why don't you just use mirrorM
  #3
Senior Member
 
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 21
eugene is on a distinguished road
why don't you just use mirrorMesh? it does everything including the merging for you.
eugene is offline   Reply With Quote

Old   March 25, 2008, 22:33
Default Thanks, doing the transformati
  #4
Member
 
Andrew King
Join Date: Mar 2009
Location: Perth, Western Australia, Australia
Posts: 82
Rep Power: 17
andersking is on a distinguished road
Thanks, doing the transformation in two steps worked, I thought I may have missed something.

As for mirrorMesh I actually need to rotate the mesh 180 degrees, not mirror it (though I realize that's not clear in my post).

cheers,
Andrew
__________________
Dr Andrew King
Fluid Dynamics Research Group
Curtin University
andersking is offline   Reply With Quote

Reply

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
how to set periodic boundary conditions Ganesh FLUENT 15 November 18, 2020 07:09
[snappyHexMesh] Snappyhex mesh: poor inlet mesh Swagga5aur OpenFOAM Meshing & Mesh Conversion 1 December 3, 2016 17:59
[snappyHexMesh] SnappyHexMesh no layers and no decent mesh for complex geometry pizzaspinate OpenFOAM Meshing & Mesh Conversion 1 February 25, 2015 08:05
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 12:55
help: the volume mesh has highly skewed elements xiaofish FLUENT 3 September 18, 2007 10:51


All times are GMT -4. The time now is 04:54.