Airfoil leading edge radius

RandomGuy88

Does anyone know how to determine the leading-edge radius of an airfoil using just the x y coordinates.

boneh3ad

You could just do a curve fit and then find it analytically...

AIR&SPACE

I know you can do it in XFoil...

ie:
1) Start XFoil
2) type "NACA 0012"
3) type "OPER"
4) hit "enter/return" key
5) type "GDES"
6) a window pops up:

RandomGuy88

Do you know if there is a way to output the value of rLE from XFOIL. I need the value of the leading edge radius for a code I am writing and would prefer to not have to enter that value manually..

AIR&SPACE

I knew I'd find it eventually... had to find my book first.

Essentially, if you have a NACA 4 series then NACA ABCD, where CD gives the max thickness, t.

Then: [itex]R_{LE}=1.1019t^{2}[/itex]

AIR&SPACE

And if all you have is x-y coordinates then you should be able to find 't' by the thickness distribution (assuming you know it's a NACA 4-series)

[itex]\pm y_{t}=\frac{t}{0.20}\left(0.29690 \sqrt{x}-0.12600x-0.35160x^{2}+0.28430x^{3}-0.10150x^{4}\right)[/itex]

The source: Theory of wing sections: including a summary of airfoil data By Ira H. Abbott, Albert Edward Von Doenhoff

akallabeth

Hey! had more or less the same problem, do you think the equation given by Abbott gives an appropriate value if it's not a NACA four digit profile ? For example for normal nowadays aircrafts ? (I don't know what kind of profile I have)