Coefficient of lift formula

[JWSiow]

Hi,

i have to find a formula for the coefficient of lift that has the angle of attack and wing shape (airfoil shape) in it. Also, where can i find airfoil shapes for different planes?

Thanks

 

[rcgldr]

This should get you started, 1550 airfoils:

http://www.ae.uiuc.edu/m-selig/ads.html

Do a web search for "airfoil polar", and you should get a few good hits.

The size of the air foil affects coefficient of lift (Reynolds effect). Also it's probably better to use effective angle of attack, which is defined to be zero at the angle of attack that results in zero lift.

The main things to look for are speed range, and lift to drag ratio, at least for gliders (both full scale and models). For small powered civilian aircraft, efficiency is often traded off to ease manufacturing, such as a flat bottom airfoil. High speed aircraft need low drag more than a good lift to drag ratio, especially super-sonic aircraft.

 

[JWSiow]

so is there a formula for the coefficient of lift that has wing shape and an angle of attack in it?

 

[rcgldr]

so is there a formula for the coefficient of lift that has wing shape and an angle of attack in it?

It's more complicated than that. I'm looking for one, however here's a link to a site with a program you can mess with, it includes lift and coefficient of lift, but not drag.

http://www.lerc.nasa.gov/WWW/K-12/FoilSim/index.html

 

[rcgldr]

Here's a java applet link:

http://www.mh-aerotools.de/airfoils/javafoil.htm

Another program, but more difficult to use:

http://xflr5.sourceforge.net/xflr5.htm

 

[FredGarvin]

so is there a formula for the coefficient of lift that has wing shape and an angle of attack in it?

No. There isn't. The particulars regarding angle of attack and airfoil shape are rolled into the coefficient. It's a measured value in a wind tunnel or estimated via flow modeling.

 

[JWSiow]

thanks heaps everyone :D

 

[F1Guille]

Erm Yeah there is, Cl = Cl(2d slope) * (AR/AR+2)*aoa