CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

inverted cells in Gambit

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

LinkBack Thread Tools Search this Thread Display Modes
Old   June 30, 2005, 12:06
Default inverted cells in Gambit
Posts: n/a
Hello all,

I would be very grateful for some help here if anyone knows how.

I'm building up a structured mesh consisting of a number of connected volumes. Some of these volumes however, when meshed, report inverted (negative volume) elements. Some of these I realize are because the volume geometries are not ideal for obtaining a structured mesh and I have tried my best to improve them or the way in which they are meshed. Some of the volumes, however, are relatively simple in geometry and should be allowing nicely structured meshing yet report every element of the mesh to be highly skewed and inverted.

What I am wondering is first of all why Gambit is doing this and secondly whether there is any tool in Gambit that can amend these inverted cells. I've tried the mesh smoothing tool but to no avail.

Fluent cannot read the mesh structure I have buit and I am sure it is due to this issue. The error reported is 'Cell Centroid is xc 300.876183 yc 10.127939 zc 10.439100WARNING: no face with given nodes. Error: Build_Grid: grid error. Clearing partially read grid.

Error: Null Domain Pointer'

I would be extremely grateful if anyone can help me here.

Thanks a lot.

  Reply With Quote

Old   June 30, 2005, 15:42
Default Re: inverted cells in Gambit
Posts: n/a
The only thing you can do is remesh your geometry. A lot of times what happens is there are edges or vertices that are really close together. When you go to apply a mesh to these faces, then it puts a node at each vertice, and these are extremely close relative to the size of the mesh you want, which creates skewed elements. Use the examine mesh tool... button at the bottom right of the screen... to locate the problem areas and understand what's going wrong that way you can figure out what you need to do to fix it.

Goodluck, Jason
  Reply With Quote

Old   July 2, 2005, 04:52
Default Re: inverted cells in Gambit
Posts: n/a
thanks a lot Jason - a gentleman
  Reply With Quote

Old   July 3, 2005, 22:58
Default Re: inverted cells in Gambit
Posts: n/a
well when u r creating a sturctured mesh , you got to be shrewd for complecated geometries, the very first thing that you can do (if u r not already doing) is to spend time on thinking how you can further subdevide the geomtery into smaller volumes, with the property that each subvolume is a topological cube. (that is it should have 8 vertices or 4 in 2d, and 6 faces).

so if u have a cube and u substract a sphere from it, it is not a topological cube since it might show u 8 vertices but now it has 7 faces.

once this thing is done, and all the faces are connected, creating a structured emsh is then a work of minutes if not of seconds.

  Reply With Quote


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
Counting the number of cells in GAMBIT Ravi Doddas FLUENT 4 May 1, 2013 22:51
[snappyHexMesh] snappyHexMesh won't work - zeros everywhere! sc298 OpenFOAM Meshing & Mesh Conversion 2 March 27, 2011 21:11
physical boundary error!! kris Siemens 2 August 3, 2005 00:32
Continuously growing cells with Gambit? Regert FLUENT 6 May 10, 2001 04:01
Dead cells created on edges when a grid file is generated in GAMBIT and imported into FLUENT4 Isaac Manohar Ch. FLUENT 1 June 2, 2000 04:58

All times are GMT -4. The time now is 14:10.