1. 3D Dynamic Stall Modelling on the NREL phase VI Parked Blade ALVARO GONZALEZ XABIER MUNDUATE 47th AIAA Aerospace Sciences Meeting and Exhibit Orlando, Florida, 5 – 8 Jan 2009

2. Contents Background and Motivation How DS differs 2D-3D: Experimental analysis dynamic stall  2D S809 aerofoil sinusoidal pitching  Parked Blade under the same motions Why DS differs 2D-3D: Dynamic stall modelling Parked blade Conclusions

3. Background and Motivation Understanding of the 3D unsteady aerodynamics.  Particularly dynamic stall on a Parked Blade. Reduce uncertainty on loads prediction.  Current deviations up to 30% on loads calculations. Traditionally “loads envelop” implies Parked blade unsteady aerodynamics loads to be a design driver that constrain the blade platform tailoring. Wind turbine blade unsteady load calculations still relay on 2D sectional steady data.

4. How and Why 3D Dynamic Stall 2D S809 AEROFOIL sinusoidal oscillatory pitching from OSU. PARKED BLADE NREL PHASE VI Sequence O, the same sinusoidal oscillatory pitching than OSU. BASED ON 2D S809 STEADY DATA from OSU. BASED ON SECTIONAL PARKED BLADE STEADY DATA NREL PHASE VI Sequence L. 3D DYNAMIC STALL STUDY

5. NREL phase VI parked blade experimental data NREL phase VI Parked blade Sequence O.  Sinusoidal motions of the blade at 12 o’clock position.  Oscillations AOA=8±10 deg and AOA=20 ±10 deg  30% 47% and 80% blade span sections  Low and high reduced frequency pitching motions: k= 0.025 and k= 0.075.

6. How DS differs 2D-3D:Experimental analysis dynamic stall Parked blade 30% section. AOA=8±10deg. k=0.025

7. How DS differs 2D-3D:Experimental analysis dynamic stall Parked blade 47% section. AOA=8±10deg. k=0.025

8. How DS differs 2D-3D:Experimental analysis dynamic stall Parked blade 80% section. AOA=8±10deg. k=0.025

9. Why DS differs 2D-3D: Dynamic stall modelling Cm Prediction Parked blade 30% section. AOA=8±10deg. k=0.025 Cn Prediction Parked blade 30% section. AOA=8±10deg. k=0.025

10. Why DS differs 2D-3D: Dynamic stall modelling Cm Prediction Parked blade 47% section. AOA=20±10deg. k=0.025 Cn Prediction Parked blade 47% section. AOA=20±10deg. k=0.025

11. Why DS differs 2D-3D: Dynamic stall modelling Cm Prediction Parked blade 80% section. AOA=20±10deg. k=0.025 Cn Prediction Parked blade 80% section. AOA=20±10deg. k=0.025

12. Conclusions The experimental comparison between the unsteady 2D aerofoil and the NREL parked blade sections has shown the necessity to consider the blade geometry effects. It has been shown that Dynamic stall computations based on 2D aerofoil data may over predict forces and moments, especially near the root. The modelling results have confirmed that 3D Dynamic stall follows its steady parked blade values. It may be concluded that 3D Dynamic stall on a parked blade can be simulated, as referred to forces and moments, based on a 2D simulation with the appropriated inputs.

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