rotational drag and lift coefficients

Dear all

I am reading Aerodyn manual and trying to use it. Actually, I am not professional and have ambiguities about using Cl and CD in either 2D or 3D?

As the input of Aerodyn, should I read rotational Cl and CD or 2D is enough?

Best regards,

Zeinab

Dear Zeinab,

In the rotating environment of a wind turbine blade, airfoils likely don’t behave as they do in a 2D environment, at least for much of the blade span. As such, for more accurate predictions from lifting line aerodynamics models, I would generally recommend applying a 3D rotational augmentation correction. In the absence of more information, you can use NREL’s AirfoilPrep or AirfoilPreppy tools to apply standard rotational augmentation corrections, e.g. the Du and Selig model.

Best regards,

Dear Dr. Jonkman

Thank you very much for your response!

About CL and CD in 3D, as I read about the method of du an selig, there is a Lambda=tangential velocity/relative wind velocity which interfere in FL computation. As I realized Airfoil prep is used before Aerodyn code so what about this relation if either wind or rotation changes? do we need to re-compute 3D CL and CD for every change in wind velocity or it is considered in Aerodyn Code and it doesn’t need to read Airfoil prep when Wind or rotation changes?

Best regards,

Zeinab

Dear Zeinab,

I would normally recommend using fixed “nominal” values and not recalculating the rotational augmentation for different wind or rotational speeds, but you could always check the sensitivity of the results to different values. A similar question was asked and answered in the following forum topic: http://forums.nrel.gov/t/help-needed-in-airfoil-prep/1838/2.

Best regards,