Test validation- Flap at power curve knee

Hello, I am comparing modeling results to field test data with a new rotor on a Zond Z-48 machine (variable-speed, full-span pitch). I am over-predicting (greater than 10%) the mean flap loads at the knee of the curve. It seems that the real turbine is pitching sooner than the model. I have attempted the following changes:

  1. change fine pitch setting (some effect, but not enough)
  2. lower pitch control rpm set point below rated generator speed (some effect, but drops power too low above rated)
    Do you have any other suggestions?

Thank you for your assistance.

What software are you using to model the turbine?

Hi Marshall,

I am using a version of FAST that I modified to accept curved blades.

If you were using a standard version of FAST, I may have been able to help a little, but if you’ve added curved blades and, I assume, live twist, your problem could be from any of a number of things. You could have modified FAST incorrectly, your airfoil data might be inaccurate, you could have other modeling errors, your control system could be implemented incorrectly, or you might be operating outside the valid realm of the aerodynamic theory.

Other than doing a thorough review of the theory you used for the FAST modifications, a review of the software implementation, and a review your model, there’s nothing I can do for you. I’m sorry, but I don’t have a spare month or two for this. :astonished:


Hi Marshall,

Thank you for the comments and I understand that it is a can a worms with a new implementation. I’ve tried several tweaks to the model, in the aero, structure, and controller, but I haven’t found anything to get the model pitching sooner and lower the flap load at rated. I thought someone out there might have seen this before and might have a suggestion.