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

Converting 3-D NACA Wind tunnel test data to 2-D data

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 5, 2014, 07:50
Default Converting 3-D NACA Wind tunnel test data to 2-D data
  #1
New Member
 
M. Abdul Akbar
Join Date: Feb 2013
Posts: 19
Rep Power: 11
akku is on a distinguished road
Hi,

For the purposes of my work, I need to get lift and drag coefficients of certain NACA airfoils for certain Reynolds Number's. However, the constraints of the wind tunnel at my lab does not permit a 2-D (infinite span) test. I can only fit a smaller sized specimen which will inevitably lead to 3-D effect by vortices at the ends. My questions is, how can I convert the 3-D (finite span) lift and drag coefficients obtained from the wind tunnel test to a 2-D (infinite span) ????.

Please excuse my ignorance on aerodynamics.

Thanks in advance.
akku is offline   Reply With Quote

Old   August 5, 2014, 09:43
Default
  #2
Senior Member
 
Troy Snyder
Join Date: Jul 2009
Location: Akron, OH
Posts: 207
Rep Power: 17
tas38 is on a distinguished road
It may be possible to reduce the vortex induced drag by fitting your 3d experimental airfoil with winglets. The results should then compare better with 2d data.
tas38 is offline   Reply With Quote

Old   August 5, 2014, 10:11
Default
  #3
Member
 
Join Date: Dec 2012
Posts: 92
Rep Power: 11
beer is on a distinguished road
In our university they just mount the wing between two walls. According to Helmholtz a vortex can end on a wall and you get rid of the wind tip vortex. If you can't do that you can calculate back from your wing with the theory for induced drag to a 2D-wing. This works as well but is obviously more error prone and more work.
beer is offline   Reply With Quote

Old   August 5, 2014, 20:55
Default
  #4
New Member
 
M. Abdul Akbar
Join Date: Feb 2013
Posts: 19
Rep Power: 11
akku is on a distinguished road
Thanks for the replies.

Hi Beer,

I hope you mean the correction calculations as shown in this page, right ???

http://people.rit.edu/pnveme/EMEM682n/review/liftcoeff.html


When you say it is error prone, do you mean to say that it is more prone to calculation mistakes or that the results may be inaccurate. If it is about the results being inaccurate, do you have any idea of how much the results may vary from the actual ???

Thanks in advance
akku is offline   Reply With Quote

Old   August 5, 2014, 22:27
Default
  #5
Member
 
Join Date: Dec 2012
Posts: 92
Rep Power: 11
beer is on a distinguished road
Hi

The page shows pretty much what I meant to say, but not exactly. What you want to know is the red arrow called L in the picture of the wing with the forces. It is the "real" lift force which is rotated by the wing vortex. If you merge the equations for lift and drag (0 degree and induces drag) you can find a correction factor for the lift coefficient not just for the lift coefficient slope.
To your question: both. But I assume you are able to calculate that problem without making mistakes there. What I meant is error prone can be seen at the end of the page. A wing is almost never perfectly elliptic. So you have to guess, measure or calculate the Oswald factor. There are some good approximation (I remember using them at uni) for differently shaped wings based on empirical equations.
I think the error of these should be small because the equations are approved by the FAA, at least AFAIK.
One other remark: I just read through your first question again. The fact that you use NACA can help you solve your problem. You can try to find lift and drag data on the internet and compare it to your experimentally generated and corrected data to see if your calculations are right.
beer is offline   Reply With Quote

Reply

Tags
drag, finite span, infinite span, lift, wind tunnel

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
flow in cyclic wind tunnel yogesh@cfd Main CFD Forum 0 November 8, 2010 04:28
OF 1.6 | Ubuntu 9.10 (64bit) | GLIBCXX_3.4.11 not found piprus OpenFOAM Installation 22 February 25, 2010 13:43
Test case data Snegan Main CFD Forum 3 June 14, 2006 08:56
Virtual Wind Tunnel in FLUENT ND FLUENT 0 April 7, 2006 07:43
Wind Tunnel Website now online Mike Worthey Main CFD Forum 0 June 6, 2000 02:27


All times are GMT -4. The time now is 18:10.