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

negative drag monitored, but positive in post pro

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 18, 2008, 22:47
Default negative drag monitored, but positive in post pro
  #1
hugo
Guest
 
Posts: n/a
Have anybody encountered the same strange problem in CFX 11.0? When I was monitoring the drag force of a flapping airfoil, the drag was negative, however I stoped the calculation to postprocess it, the drag turned out to be positive.How come? The lift coefficient and the moment coefficient were alright and reasonable. Can anyone give me some advice how could this happen? The other problem is when I used cel areaInt(Wall Shear X)to obtain the wall shear, the error: ERROR The following unrecognised name was referenced: areaInt.. popped up. Is there something wrong with the expression? But I used it before and it was ok.
  Reply With Quote

Old   December 22, 2008, 04:04
Default Re: negative drag monitored, but positive in post
  #2
hugo
Guest
 
Posts: n/a
http://img242.imageshack.us/img242/6...ficientwm7.png[/IMG][/URL]

No one knows as to how could it happen? I am simulating a pithcing airfoil with CFX, but the monitored drag sometimes is negative and not reasonable. I get lift and moment well except drag. When the drag is negative I stop the simulation to post process it, surprisingly it is positive! Can anyone tell me?
  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
anyone has got this paper? Al Main CFD Forum 3 October 8, 2007 02:04
Negative drag on a yacht Sail section Iain Robertson CFX 3 March 27, 2007 09:06
How to determine the Drag Coefficient using POST? Hans CFX 0 January 18, 2006 20:53
Drag Coefficient in POST. Gloria Gaynor CFX 1 June 17, 2004 04:31
Inviscid Drag at subsonic, subcritical Mach # Axel Rohde Main CFD Forum 1 November 19, 2001 13:19


All times are GMT -4. The time now is 20:50.