Torque and power coefficients

Dear NREL team

I am using FAST with simulink. I got Power coefficient as an output from FAST. Also I calculated the powercoefficient based on Rotor Aerodynamic torque, Low Speed Shaft velocity and incomming wind speed (Aerodynamic Power/Available power) but they are not equal. Why ?
Is this power coefficient (FAST output) similar to what WT-Perf or Aero-Dyn can provides. I mean if I calculate the CP curve by WT-Perf and I find the relevant CP from this curve (WT-Perf output), based on the TSR and Pitch angle of FAST model then the result should be equal to FAST output.

Regards
Mahmoud

Phd Candidate
NTNU-Trondheim Norway

Dear Mahmoud,

We’ve had a discussion on this forum regarding how FAST calculates RotCp. Please see the forum topic found here: http://forums.nrel.gov/t/betz-law-and-rotcp/259/1. Hopefully this clarifies things a bit.

The power coefficient predicted by WT_Perf is calculated purely from steady state aerodynamics. FAST should produce similar results to WT_Perf under these conditions (but not identical results because the aerodynamic algorithms are slightly different).

I hope that helps.

Best regards,