CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > ANSYS Meshing & Geometry

(ICEM)Negative volumes instead of thiner layer

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 10, 2009, 06:11
Cool (ICEM)Negative volumes instead of thiner layer
  #1
cbr
New Member
 
Join Date: Aug 2009
Posts: 10
Rep Power: 7
cbr is on a distinguished road
Hi,
I'm preparing 2-D mesh for a wing in ICEM
I need to 7-times decrease thickness of first near-wall layer, because max(y+) is 7 in my result file. But I'm getting negative volume when I set new thickness.
Please help me to fix it, thanks in advance!
cbr is offline   Reply With Quote

Old   August 10, 2009, 14:46
Default Kate Moss Thin
  #2
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,662
Blog Entries: 1
Rep Power: 35
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
There is a known defect (see the release guide) about the quality metrics sometimes calling thin hexas inverted…

If your solver is structured, do the checks in the blocking tab, and if the very thin elements look (visually) ok, proceed to your solver and check it there.

If your solver is unstructured, do the checks on the unstructured mesh (Edit Mesh tab)...

On the other hand, you could actually be having a problem with the mesh…

If so, then I am guessing that you probably have a slight misalignment of parts (curves not aligned with surfaces to the same tolerance as your first cell height) and the mesh is trying to follow too closely. In certain situations, refining the mesh below the scale of the geometry quality can invert the boundary layer in the last element when projection changes from one entity to the other. If that is what you find (visually), setting projection limit can really help.
PSYMN is offline   Reply With Quote

Old   August 19, 2009, 03:35
Default
  #3
cbr
New Member
 
Join Date: Aug 2009
Posts: 10
Rep Power: 7
cbr is on a distinguished road
Thanks Simon,

I have invented also another method- scale initial geometry 10 times (for example), create mesh for scaled geometry, open the mesh in pre and scale mesh 0.1 to initial size. Correct volume of thin elements keeps at that transformation in CFX-pre
cbr is offline   Reply With Quote

Old   August 20, 2009, 08:45
Default
  #4
cbr
New Member
 
Join Date: Aug 2009
Posts: 10
Rep Power: 7
cbr is on a distinguished road
Everithing great is simple

another one solution of this problem is restart ICEM
cbr is offline   Reply With Quote

Old   August 20, 2009, 17:35
Default Reboot the shuttle...
  #5
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,662
Blog Entries: 1
Rep Power: 35
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
Do you recall that time a few years back when the Space Shuttles computers were acting up and there was a tense 15 minutes while the astronauts had to sit in the dark as the orbiters computers were rebooted? There was some worry about if they would reboot properly, but they did, and then everything was fine.

I often think that as I reboot anything… If it was a good enough solution for NASA…
PSYMN is offline   Reply With Quote

Old   August 21, 2009, 04:26
Default
  #6
cbr
New Member
 
Join Date: Aug 2009
Posts: 10
Rep Power: 7
cbr is on a distinguished road
I'm almost astronaut then, hehe
cbr is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Default Faces on Boundary Layer axel Open Source Meshers: Gmsh, Netgen, CGNS, ... 8 February 17, 2011 08:47
To thin boundary layer? Luk CFX 3 February 27, 2009 04:22
errors Fahad Main CFD Forum 0 March 23, 2004 14:20
Boundary Layer Flow Paradox Wen Long Main CFD Forum 3 September 24, 2002 08:47
union of volumes CHUBBY FLUENT 2 May 4, 2001 06:31


All times are GMT -4. The time now is 07:20.