1. European Wind Energy Conference and Exhibition 2006 Athens, Greece EWEC’06 Athens 27 February-2 March 20061/16 Advanced Aeroelastic Modeling of Complete Wind Turbine Configuration in View of Assessing Stability Characteristics V.A.Riziotis and S.G.Voutsinas National Technical University of Athens School of Mechanical Engineering Fluids Section NTUA

2. EWEC’06 Athens 27 February-2 March 2006 2/16 NTUA Overview of the Presentation

3. EWEC’06 Athens 27 February-2 March 2006 3/16 NTUA

4. EWEC’06 Athens 27 February-2 March 2006 4/16 NTUA wind turbine modes are excited, – by individual blade pitch (rotor modes and tower fore aft mode) – by point force applied at tower top (tower modes) duration of excitation 15sec pitch amplitude 2 o tower force amplitude 2.5 ton damping extracted from transient loads time-series Non-linear damping identification 15 s 5 rev Excitation Method

5. EWEC’06 Athens 27 February-2 March 2006 5/16 NTUA ΔtΔt ΔtΔt t0t0 -ζ Ω n moving block method Damping Identification Methods

6. EWEC’06 Athens 27 February-2 March 2006 6/16 NTUA Hilbert method A(t): envelope signal 90 0 phase shift Damping Identification Methods

7. EWEC’06 Athens 27 February-2 March 2006 7/16 NTUA 1 st tower lateral bending Comparison with Measurements

8. EWEC’06 Athens 27 February-2 March 2006 8/16 NTUA 1 st tower longitudinal bending Comparison with Measurements

9. EWEC’06 Athens 27 February-2 March 2006 9/16 NTUA reduction of damping beyond 16m/s is associated with the inability of the damping identification method to predict well the damping of spectrally close modes Comparison with Measurements

10. EWEC’06 Athens 27 February-2 March 2006 10/16 NTUA r/R = 0.40 r/R = 0.85 Comparison with Measurements

11. EWEC’06 Athens 27 February-2 March 2006 11/16 NTUA 1 st regressive rotor lead-lag Comparison with Measurements

12. EWEC’06 Athens 27 February-2 March 2006 12/16 NTUA 1 st progressive rotor lead-lag Comparison with Measurements

13. EWEC’06 Athens 27 February-2 March 2006 13/16 NTUA 1 st tower lateral bending1 st tower longitudinal bending Comparison of damping Identification Methods

14. EWEC’06 Athens 27 February-2 March 2006 14/16 NTUA 16 m/s12 m/s Comparison of damping Identification Methods

15. EWEC’06 Athens 27 February-2 March 2006 15/16 NTUA Conclusions

16. EWEC’06 Athens 27 February-2 March 2006 16/16 NTUA Acknowledgements European Commission for funding this work under contract NNK5-CT2002-00627 (STABCON project) STABCON project partners for publishing of the paper