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# Lift to drag and angle of attack

## Lift to drag and angle of attack

(OP)
For a given NACA airfoil is it available any formula which relates the (L/D) ratio with the angle of attack?

### RE: Lift to drag and angle of attack

Yes, there are many methods for calculating the theoretical values.  There is also a lot of published experimental data for airfoils, especially NACA foils.  Your best bet would probably be to take a look at this data.

Since you are asking I would assume you are not looking to come up with the theoretical equations, so check out www.worldofkrauss.com/ They have lots of Cl and Cd data for different AOAs for tons of foils.  They allow you to compare several foils.

### RE: Lift to drag and angle of attack

Are you talking about a wing or a loose airfoil?

Every airfoil will behave slightly different, but if they're not to thick on may use some linear theories.

There are many theoretical texts on this. The drag should go quadratically with lift, while lift (before stalling) goes linear (slope about 2*pi) with the angle of attack.

Have a look at
http://en.wikipedia.org/wiki/Lift-induced_drag

Parasite drag
Induced drag
The laminar bucket
Linear lift theory

A classical text on this issue is:
Abbott, Ira H., and Von Doenhoff, Albert E. (1959): Theory of Wing Sections. Dover Publications Inc., New York, Standard Book Number 486-60586-8

### RE: Lift to drag and angle of attack

(OP)
Thanks guys for replies.

aafuni,
Frankly I was looking for a theoretical correlation, anyhow your link is very interesting.

### RE: Lift to drag and angle of attack

I like that site to get some rough comparisons and narrow down my options before I move into the more in depth analysis.

### RE: Lift to drag and angle of attack

i don't think there's a general theoretical solution.

i think the most you'll find is curve fits to experimental results.

the lift side is pretty easy, the drag side is quite complex ... 2D wing section or 3D wing ?  a 3D wing adds "drag due to lift"

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