Aerodynamic Torque calculation


I need to know the magnitude of the aerodynamic torque. Please tell me how FAST or AeroDyn calculates this parameter. Can I have the aerodynamic torque magnitude as a FAST output data like other parameters (e.g. LSShftMxa,HSShftTq,…)? Or I have to calculate it myself? I have read the FAST manual but I couldn’t find my answer.
By the way I have read the useful post (Resistant moment of the rotor and of the electric generator), where you mentioned how LSShftTq and HSShftTq are obtained.

Thank you for your attention and supports, regards

Alireza Nik

Dear Alireza,

You cannot currently output the aerodynamic torque directly from FAST; instead, the reaction torque within the shaft can be output (LSShftTq=RotTorq), as explained in the forum topic you referred to:

Without changing the source code to output the aerodynamic torque directly, you could derive the aerodynamic from available FAST outputs in a couple ways:

  1. Add the rotor inertia term (due to acceleration/deceleration) to the reaction torque output. That is, solve the equation from the forum topic you referred to, LSShftTq = T_Aero – J_Rotor*Alpha, for T_Aero. If the rotor is flexible, this result will only be approximate, but may be accurate enough for your needs.

  2. Time-average the reaction torque output over time scales large enough to average-out the variations in rotor motion; this result should be the average aerodynamic torque.

Best regards,

Dear Jason

I really thank your attention and fast reply to my post.


Alireza Nik