NREL 5MW Baseline Turbine: Negative AoA for high wind speeds

Wind & Water Rotor Aerodynamics
1

Hi all,

We were currently simulating the 5MW NREL Baseline Turbine as reference case for further studies in passive flow control. One interessting case is at about 18 m/s with 12.1 RotSpeed and 14.92 BlPitch(1,2,3). We were wondering that the angles of attack at RP 12-14 for a turbulent wind field IEC1 A 18m/s had negative values of about -1 to -2 degree. Is that the design point to achieve constant values for torque and and power output or are we making a mistake here?

Thanks a lot for your response

Andreas Ferber

2

Dear Andreas,

This is to be expected. At high wind speeds, the blade-pitch angle will increase to keep the power and rotor speed at rated values (5 MW and 12.1 rpm, respectively). While the overall torque and thrust will remain positive in this case, the angles of attack will become negative at the outer-most portions of the blade.

I hope that helps.

Best regards,