CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Volume Mesh - Skewness?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 6, 2007, 06:30
Default Volume Mesh - Skewness?
  #1
David Banks
Guest
 
Posts: n/a
Hi everyone

I have successfully imported an STL file of a seabed bathymetric shape,made up from several faces stitched together and wrapped with 5 other flat faces to create a volume.

I already have face meshes and need to mesh the volume now but keep getting the same message;

"Initialisation failed; perturb boundary nodes and try again:

Error: TG_MESH_DOMAIN failed with error code 1

Error: Tetrahedral meshing has failed for volume v_volume.1 This is usually caused by a problem in the face meshes. Check the skewness of your face meshes and make sure the face mesh sizes are not too large in areas of small gaps"

Does this mean the mesh is no fine enough in certain faces? Can this be easily fixed?

Cheers

Dave

  Reply With Quote

Old   August 6, 2007, 07:21
Default Re: Volume Mesh - Skewness?
  #2
nino
Guest
 
Posts: n/a
no it means that you have high-skewed cells. Check if you have small edges or small faces
  Reply With Quote

Old   August 6, 2007, 08:12
Default Re: Volume Mesh - Skewness?
  #3
David Banks
Guest
 
Posts: n/a
I have some relatively small faces. Do I have to reduce the amount of elements in the smaller cells?
  Reply With Quote

Old   August 6, 2007, 09:31
Default Re: Volume Mesh - Skewness?
  #4
nino
Guest
 
Posts: n/a
no. With this small faces, you enforce Gambit to mesh them, even if your cell size isn't appropriate. I would either refine your mesh on those faces (and use a Size Function for controling your mesh), or try to merge them (if it is possible)
  Reply With Quote

Old   April 4, 2009, 19:53
Default
  #5
New Member
 
bilquise
Join Date: Mar 2009
Posts: 14
Rep Power: 17
cfdproject is on a distinguished road
Hello,
I am trying to mesh the continuum between the fins. and I am getting the same error.
I tried to assigning a size function I have a error of Equiskew Angle>0.97
Can anybosy help me
Thanks
cfdproject is offline   Reply With Quote

Old   April 5, 2009, 19:54
Default
  #6
Member
 
Join Date: Mar 2009
Posts: 35
Rep Power: 17
panda is on a distinguished road
you may try to use Tgrid to mesh the volume, it would be easier to generate a good quality mesh.
panda is offline   Reply With Quote

Old   April 6, 2009, 00:43
Default
  #7
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 3,297
Rep Power: 41
-mAx- will become famous soon enough
The question is why do you get cell's equiskew angle over 0.97.
It is possible that you have short edges, small angle etc...
Have you tried with other parameters in size function?
Have you tried without size function?
-mAx- is offline   Reply With Quote

Old   April 6, 2009, 19:45
Default
  #8
New Member
 
bilquise
Join Date: Mar 2009
Posts: 14
Rep Power: 17
cfdproject is on a distinguished road
My question is how would I be able to deal with a error message saying that the Equisize angle>0.97. and therefore the geometry could not be meshed.
I did try the geometry with varying size function and also without size function but I end up getting the same message..
Please help
Thank you
Bilquise
cfdproject is offline   Reply With Quote

Old   April 7, 2009, 00:28
Default
  #9
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 3,297
Rep Power: 41
-mAx- will become famous soon enough
Go and examine your mesh with the icon at the bottom right.
Select skewness and set the lower value with 0.9 (cells with higher value, may cause problems with the convergence)-
Gambit will show the cells with skewness over 0.9.
It is a good way for knowing where is the problem
-mAx- is offline   Reply With Quote

Old   April 9, 2009, 00:37
Default
  #10
New Member
 
bilquise
Join Date: Mar 2009
Posts: 14
Rep Power: 17
cfdproject is on a distinguished road
Thanks Max.
it works
cfdproject is offline   Reply With Quote

Old   February 17, 2011, 08:33
Default
  #11
New Member
 
bing
Join Date: Feb 2011
Posts: 5
Rep Power: 15
onionmon is on a distinguished road
Hi, I am having the same problem here.

I am meshing a 3D volume using the Tet/Hybrid on a TGrid. I have cleaned my geometry to remove small edges and small areas and small angles. I have implemented size functions where applicable to mesh small areas. My face mesh check shows no elements with an equisize skew > 0.9. A check using geometry command button>check vertices; geometry command button>check edges; geometry command button>check faces; geometry command button>check volumes show 0 failures in the validity check for all different geometries.

What else am I doing wrong for this not to mesh??

Thanks ahead for your help!
onionmon is offline   Reply With Quote

Old   February 19, 2011, 04:20
Default
  #12
New Member
 
bing
Join Date: Feb 2011
Posts: 5
Rep Power: 15
onionmon is on a distinguished road
OK, I solved my problem. Here is my follow up.

I discovered a vertex from one surface that was very close to another surface so that a 3D tet element was not able to be created during 3D meshing. The vertex closeness to a surface is shown in a rough diagram below.


Code:
|-----|    |-----|
|       |_._|       |
|---------------|
I solved the problem by zooming out so I can see my entire system. I noticed a white vertex (multi-edged vertices are purple) sitting by itself in the middle of a face. I created a geometry and boolean-subtracted it from my base geometry so that the vertex was removed. Then I was able to mesh.
onionmon 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
Moving mesh Niklas Wikstrom (Wikstrom) OpenFOAM Running, Solving & CFD 122 June 15, 2014 06:20
[ICEM] Generating Mesh for STL Car in Windtunnel Simulation tommymoose ANSYS Meshing & Geometry 48 April 15, 2013 04:24
[snappyHexMesh] snappyHexMesh won't work - zeros everywhere! sc298 OpenFOAM Meshing & Mesh Conversion 2 March 27, 2011 21:11
ICEM Tetra mesh, Size reduction and Skewness problem Catthan ANSYS Meshing & Geometry 6 December 5, 2010 19:39
ICEM 12 CFD help creating volume mesh from stl EmpError ANSYS 0 November 13, 2010 06:38


All times are GMT -4. The time now is 19:49.