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

[Gmsh] GMSH 3D hibrid mesh: ill elements, negative volumes and incorrectly oriented faces

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 18, 2023, 08:09
Exclamation GMSH 3D hibrid mesh: ill elements, negative volumes and incorrectly oriented faces
  #1
New Member
 
Sergi Giménez
Join Date: Feb 2023
Posts: 2
Rep Power: 0
Lligres is on a distinguished road
Howdy all,
This is my first post, so I hope I am doing everithing wright .
I'm designing a 3D mesh of a wing using gmsh in order to run it on Openfoam. I made a hibrid mesh, so the elements around the wing are hexahedra and the elements far from it are tetrahedra; between those hexahedra and tetrahedra there is a layer of pyramids in order to combine the quadrangle faces of the structured mesh with the tetrahedra nodes (It's done by default with the Delaunay algo).
When running the algorithm I have problems, I have two error messages which are the following: "Warning : Strange edge cavity (tet is deleted)" and "Warning : 12 ill-shaped tets are still in the mesh". I managed to reduce the number of ill-shapped tets from 2000 to 12 by reducing the aspect ratio of the quadrangles in contact with the un-structured volumes (this way the pyramids and the tetrahedra sorrounding it seem to be simpler and the algorithm seems to work better), but there are still cells that have 0 or negative volume according to OpenFOAM.

On the other hand, when runing the checkMesh code on openFoam i have several errors : " ***Zero or negative cell volume detected. Minimum negative volume: -0.00053318274, Number of negative volume cells: 83 ", "***Open cells found, max cell openness: 1, number of open cells 432", " ***Number of non-orthogonality errors: 373." , " ***Error in face pyramids: 660 faces are incorrectly oriented." and "***Max skewness = 45.903898, 27 highly skew faces detected which may impair the quality of the results".

I have been working on this for several days but now I'm at a point that I don't know how to advance further. I have attached the .geo file splitted in two .txt files, as it was to heavy to upload in one.

Any help regarding these issues would be very appreciated,
Kind regards,

Sergi Giménez Herrero
Lligres is offline   Reply With Quote

Old   September 19, 2023, 13:13
Default
  #2
New Member
 
Sergi Giménez
Join Date: Feb 2023
Posts: 2
Rep Power: 0
Lligres is on a distinguished road
Next I will attach some images of the mesh, the wing and the computational domain so it may be easier for you to understand the case.

If you pay atention to the wing, you can see that it has a "c" shaped end, it's because it is a c-wing and I am studying the effects of this wingtip.

Hope it can help a bit,
Kind regards to anyone reading this,

Sergi Giménez Herrero
Attached Images
File Type: png 2D computational domain.PNG (162.3 KB, 8 views)
File Type: jpg 2D wing.jpg (200.1 KB, 13 views)
Lligres is offline   Reply With Quote

Reply

Tags
gmsh

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
[Other] error: faces are incorrectly oriented sergiopb91 OpenFOAM Meshing & Mesh Conversion 1 September 9, 2016 10:36


All times are GMT -4. The time now is 13:34.