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

Gambit - meshing over airfoil wrapping (?) problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 7, 2011, 12:00
Default Gambit - meshing over airfoil wrapping (?) problem
  #1
New Member
 
Join Date: Jul 2011
Posts: 1
Rep Power: 0
JFDC is on a distinguished road
I'm having a problem in Gambit with the mesh over an airfoil.

For most of the domain the mesh is exactly like I wanted but in a zone somewhat between the trailing edge and the maximum thickness point of the upper part of the airfoil it is causing problems.

I exported the airfoil shape from Solidworks (it is a 3d model, but the problem here is with one of the slices of that model, so this is a plane mesh like bidimensional examples).

Here is the model before the volume (and naturally face) meshing. As you can see it's a C mesh with 2 zones (=volumes) over the airfoil, one for upper and another for lower flow.
http://img607.imageshack.us/img607/5...tionsshown.png

Here is the general mesh view after the volumes being meshed. It creates negative volume elements because of the problem shown in the images below.
http://img813.imageshack.us/img813/6527/generalmesh.png

From this scale we can start noticing the problem
http://img30.imageshack.us/img30/416...emoverview.png

And comparing both the upper and lower meshes on a closer scale it is becoming more obvious
http://img163.imageshack.us/img163/7...tbehaviour.png

The lower part is an example of how it should be
http://img38.imageshack.us/img38/137...ectexample.png

And this is the problem. I don't know what it does, it seems to wrap the mesh itself and it does not respect the meshing scheme in the "j" direction, where it should have more elements closer to the wall.
http://img853.imageshack.us/img853/6...lemcloseup.png

I use the hex-map instruction to mesh the volume (and so also the "bidemensional" faces). It seems to be close to correct as the mesh nodes on the airfoil and the lines that come from the farfield are consistent, but in this zone there is obviously some problem.

When I use less elements on the vertical, "j", direction, the volumes and the meshing have no errors BUT as in this example the elements that were supposed to be in greater number near the wall are not, they gather together a little over it, but as they are in less number than in this example they don't end up wrapping themselves and the mesh is possible to be made, although it also violates the meshing scheme.

With your experience, is this a meshing scheme problem (maybe the mesh algoritm doesn't like the airfoil shape? In this case I suppose splitting the upper face into more zones would solve the problem) or do you think it is a geometrical problem (I had some of those but here it seems to be correct everywhere else)? Any ideas on how to solve it?

Many thanks!
JFDC is offline   Reply With Quote

Old   July 11, 2011, 06:59
Default
  #2
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 2,873
Rep Power: 29
-mAx- will become famous soon enough
Try to split your volumes around the airfoil (with an ellipse or whatever).
And remesh the new volumes
__________________
In memory of my friend Hervé: CFD engineer & freerider
-mAx- 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
[ANSYS Meshing] Migrating from GAMBIT to ANSYS Meshing David-CFD ANSYS Meshing & Geometry 1 April 1, 2011 06:22
[GAMBIT] Desperate student needs help meshing 3D GAMBIT model - please help! lau06165 ANSYS Meshing & Geometry 1 March 22, 2010 03:09
Gambit meshing problem nana ANSYS Meshing & Geometry 5 August 31, 2009 06:58
Meshing problem in gambit abhishek mukherjee FLUENT 1 July 22, 2008 05:23
Meshing problem in GAMBIT Vidya Raja FLUENT 0 May 21, 2006 00:31


All times are GMT -4. The time now is 18:18.