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

Gambit boundary layer distortion

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 9, 2009, 11:41
Default Gambit boundary layer distortion
  #1
New Member
 
Join Date: Sep 2009
Posts: 27
Rep Power: 7
ghost is on a distinguished road
Hi, I am trying to create a 2D flow over an airfoil using gambit and fluent.

In gambit, I split the airfoil into 6 edges, and the b/l of 5 edges can be meshed correctly. Only the final edge will have some distortion.

This leads to a slowdown in the computer system, which I assumed is caused by a lot of background calculation due to the distortion.

Attached is a picture of what I meant by distortion.



I created this 2D airfoil by importing a Solidworks IGES file, which contains a 3D model. After that I removed all faces and volumes, except the edges and vertex of one plane of airfoil. Is this method correct?
ghost is offline   Reply With Quote

Old   September 9, 2009, 14:04
Default
  #2
New Member
 
Sean Delfel
Join Date: Aug 2009
Posts: 27
Rep Power: 8
delfel is on a distinguished road
Hi ghost,

That method sounds perfect, but in my experience you almost always need to clean up the geometry in some way after importing it from CAD files. In my experience it's especially true at the trailing edge of airfoils. That mess at the trailing edge would most certainly effect your convergence and accuracy and should be cleaned up manually. I would zoom in and see if there is a blunt edge at the trailing edge and either make it sharp or create additional faces to compensate for it. Also, what does your wake mesh look like?

Cheers,
-sean
delfel is offline   Reply With Quote

Old   September 9, 2009, 21:44
Default
  #3
New Member
 
Join Date: Sep 2009
Posts: 27
Rep Power: 7
ghost is on a distinguished road
How can I actually do cleanup of the model? sorry, this is my first time using gambit.

The trailing edge is sharp as it consist of a single vertex, connecting the top half and bottom half of the airfoil.

What do you mean by creating additional faces at the T/E?

My wake mesh will be using two big rectangles and meshing them using the 'Mesh Edge' and 'Mesh Face' function, not the create b/l function.
ghost is offline   Reply With Quote

Old   September 13, 2009, 05:06
Default
  #4
Member
 
Ivan
Join Date: May 2009
Posts: 85
Rep Power: 8
ivanbuz is on a distinguished road
have you tried using a rounded T/E? that way you may also create b/l for it.
ivanbuz is offline   Reply With Quote

Old   September 14, 2009, 01:26
Default
  #5
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 2,992
Rep Power: 30
-mAx- will become famous soon enough
I am not experienced with BL, but what you can try is to split your domain from trailing edge point (the one which gives you trouble) till links extremity from your domain.
Your BL will be projected along the split edge and you won't have this distorsion anymore.
It will also enable your to better solve the wake region
__________________
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
How to use boundary layer option in gambit san FLUENT 0 May 5, 2006 00:41
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 16:55
errors Fahad Main CFD Forum 0 March 23, 2004 14:20
GAMBIT BOUNDARY LAYER Rich FLUENT 0 August 27, 2003 14:13
boundary layer thickness 98.4F Main CFD Forum 1 December 29, 2000 08:23


All times are GMT -4. The time now is 21:05.