Two questions concerning the NREL phase VI wind turbine

Hi all,

i have two questions concerning the NREL phase VI wind turbine, and i hope to receive the reply soon!

1- phase VI wind turbine has been tested at 3 deg tip pitch angle, however the blade tip has local twist of about - 1.78 deg with respect to the zero twist at 75% blade-span as found in “Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Configurations and Available Data Campaigns” .

Does this mean that the blade pitch angle equals 4.75, or else ?

2-The same refrence mention that the rated power of phase VI wind turbine is about 19.8 kW, but i found that the peak power equal about 10 kW at 3 deg pitch angle. How ths contradition can be explained?

Best regards

No - 3 degrees of tip pitch is accurate.

19.8kW is the rated power of the generator. The rotor’s peak power depends on many other things, including density, pitch, and which rotor configuration was used.

Lee Jay Fingersh

thanks Lee for your reply

i think my question was not clear so i will reformulate it.

considering the WT_PERF simulator, if i want to compare the predicted results using WT_PERF with the measured power of the NREL phase VI turbine available at 3 deg tip pitch angle, should i enter the blade pitch analysis parameter in WT_PERF as 3deg?, or enter the following:

blade pitch angle = tip pitch angle - local blade twist angle

so ----, blade pitch angle = 3 - (-1.78) = 4.78

so i enter the blade pitch angle in WT_PERF as 4.78?

i hope it becomes clear.



The tip pitch claimed in the experiment is true pitch relative to the plane of rotation. So if your twist distribution has -1.78 at the tip, then +4.78 would be needed for 3 degrees at the tip relative to the plane of rotation.

Lee Jay Fingersh

I’m trying to use WT_Perf seperately for BEM analysis for NREL Phase VI turbine Performance analysis
I got following doubts

  1. How or where to enter the number of blade segments (Not geometry info of the blade), blade is divided into in WT_Perf?
  2. Is it possible to enable 3D corrections ( which is incorporated in HARP_Opt) in WT_Perf?
  3. Some examples I noticed, they are not entering the geometry information of the tip (like radius, chord and twist) .
    4)I get an error "
    Your analysis nodes are incorrectly defined. Please review the following forum topic for an
    explaination of this error:

The radius for blade segment #4 is too far inboard for a physically realizable blade. It must
be greater than 1.56".

Can you please explain me, how to resolve it.

Dear Ijaz Fazil,

Here are my answers to your questions:

  1. The number of blade segments in WT_Perf is entered via input parameter NumSeg.
  2. I’m not sure which 3D corrections your referring to, but e.g. hub loss, tip loss, and skewed wake corrections are features that can be enabled/disabled within WT_Perf. Rotational augmentation of the airfoil data is not handled by WT_Perf, but can be considered in the airfoil data provided (by using a preprocessor like AirfoilPrep).
  3. I’m not sure I understand your question, but in WT_Perf (as in AeroDyn v12 - v14) the analysis nodes are located at the centers of the elements/segments, not at the end points, so, there is never a node defined directly at the tip.
  4. The relationship between the length of each segment (dr) and the local radius (RElm) is described in our FAQ: I know that AeroDyn v12 – v14 where very strict on ensuring that dr and RElm are compatible, but I’m not sure what logic is implemented in WT_Perf. You will have to review the WT_Perf source to confirm.

Please note that we no longer support WT_Perf, which has essentially been replaced by the standalone driver for AeroDyn v15:

Best regards,