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

Flow Result Accuracy

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

Reply
 
LinkBack Thread Tools Display Modes
Old   February 22, 2012, 11:53
Default Flow Result Accuracy
  #1
New Member
 
Jimmy
Join Date: Feb 2011
Posts: 7
Rep Power: 6
wildabyss is on a distinguished road
I was performing turbulent flow modeling with Fluent on an untapered rectangular wing with an aspect ratio of 6.6, at an Re of approximately 1e6. The airfoil is NACA0015. I used the S-A turbulence model with low-Re correction.

I performed validation using a VLM solver (AVL) for lift, moment and induced drag, and the fully turbulent flat plate solution for skin friction drag. As can be seen from the plots, the CL and CD agree pretty well. How come the CM is more than 3 times off?
Attached Images
File Type: png CL.png (12.7 KB, 13 views)
File Type: png CD.png (17.1 KB, 12 views)
File Type: png CM.png (9.5 KB, 14 views)
wildabyss is offline   Reply With Quote

Old   February 22, 2012, 17:25
Default
  #2
Senior Member
 
Martin Hegedus
Join Date: Feb 2011
Posts: 497
Rep Power: 9
Martin Hegedus is on a distinguished road
Cm is always tricky, and the hardest, to compare.

One of the better metrics is to calculate the error in the center of pressure or aerodynamic center, in your case, dxac = (cm1-cm2)/cl = (3.25e-2-1.0e-2)/1.0 = 2.25e-2. So your aerodynamic center is off by 2.25 percent of the chord. (Assuming your reference length is the chord length) This is to be expected.
Martin Hegedus 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
Flow meter Design CD adapco Group Marketing CD-adapco 3 June 21, 2011 08:33
Can 'shock waves' occur in viscous fluid flows? diaw Main CFD Forum 105 November 20, 2009 05:19
mass flow in is not equal to mass flow out saii CFX 2 September 18, 2009 08:07
reversed flow at velocity inlet / mass flow inlet ib FLUENT 1 March 26, 2007 13:11
Cavity air flow with radiation – result variable Yingchun CFX 1 November 25, 2005 12:13


All times are GMT -4. The time now is 00:11.