problem with AeroDYn 15

Wind & Water Rotor Aerodynamics
1

Dear Jason
I think i have a problem with AeroDyn 15. in this relation, i have two questions.

  1. Are Rotor aerodynamic power coefficient and power coefficient same values? if they are, with WT-PERF, i found that maximum power coefficient for WP-1.5MW is 0.5 but in simulations, sometimes it is over than 0.55. what is the problem?
  2. I use the equation (cp=RotPwr1000/((1/2)rhopiR^2*v^3)) and in this time, power coefficient exceeds than 0.6.
    i will be so grateful for your answer

Best Regards,

2

Dear Farshad,

I’m sorry, but I don’t really understand your questions. Please clarify.

Best regards,

3

Dear Jason

I am really sorry for my English!!. I need power coefficient for my simulations in FAST V8. So i use rotor aerodynamic power coefficient (RtAeroCp)‌‌‌ in AeroDyne. Although i know that it must not exceeds 0.5 but sometimes it is more than 0.55. Now i want to ask is RtAeroCp the same as power coefficient or something else?
Another question is, i use rotor power(RotPwr) in ElastoDyn for obtaining power coefficient by this relation:
cp=RotPwr1000/((1/2)rhopiR^2*v^3)
where rho is air density, R is rotor radius and v is wind velocity
this time it is more than 0.6, what is the problem?

Best regards

4

Dear Farshad,

As I explain in my post dated Feb 24, 2017 in the following forum topic: Pitch rate in Fast v7 - #13 by Jason.Jonkman, RotAeroPwr (and associated RtAeroCp) output from AeroDyn v15 within FAST v8 are derived from the applied aerodynamic loads and RotPwr output from ElastoDyn within FAST v8 (and associated RotCp from FAST v7) are derived from both the applied aerodynamic loads and inertial effects.

By nature of their calculation within the aero-elastic solution, I would only use RotAeroCp and RotCp in a time-averaged sense (RotCp must be time-averaged longer than RotAeroCp) to avoid apparent violations in the Betz limit that may occur instantaneously as a result of the calculation approach.

Best regards,