Coefficients CD,L and CD,L2^2

[pedrobri...@gmail.com]

I would like to know if the coefficients CD,L and CD,L^2 are the terms the shape the drag polar in the following shape: DPolar = (CD,L)*cd0 + (CD,L2)*cl^2 ? If not, how can I obtain them? I am currently working with high cambered airfoils and when I tried to make a curve fit to obtain (CD,L) and (CD,L^2) the result obtained contained an negative drag coefficient.  

[Aero Lab Team]

Hi,

Those coefficients are best understood by following the airfoil tutorial in our course. Here is a link to three videos that will walk you through the airfoil definition and how that includes drag: http://aero.go.usu.edu/lessons/1-6-airfoil-definition-and-analysis/

The equation for drag is: CD = CD0 + CD,L*Cl + CD,L^2*Cl^2

We find this definition more accurate than the traditional definition, which neglects the middle term on the right-hand side. It turns out that term is important in order to more accurately match drag polars.

Please let me know if you have more questions.

Thanks,

Doug