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Analysis of Vortex-induced Vibrations using a free- wake aeroelastic tool Spyros Voutsinas (*) Fangmao Zou(**), Vasilis Riziotis(*), Jun Wang(***) (*)

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Presentation on theme: "Analysis of Vortex-induced Vibrations using a free- wake aeroelastic tool Spyros Voutsinas (*) Fangmao Zou(**), Vasilis Riziotis(*), Jun Wang(***) (*)"— Presentation transcript:

1 Analysis of Vortex-induced Vibrations using a free- wake aeroelastic tool Spyros Voutsinas (*) Fangmao Zou(**), Vasilis Riziotis(*), Jun Wang(***) (*) NTUA, School of Mechanical Engineering, Greece (**) China-EU Institute for Clean and Renewable Energy, Wuhan, China (***) Huazhong University of Science and Technology, Wuhan, China EWEA Annual Event 2013 Vienna February, 4-7, 2013

2 Vortex induced vibrations 2/16 Vortex-induced vibrations & wind turbines Aeroelastic instabilities and vortex-induced vibrations can appear on wind turbine blades at stand still. 1.Negative (CL-a) slope a~90o triggers Aeroelastic instabilities 2.Large vortex structures trigger Vortex induced vibrations Du96-w-180: Skrzypiński et al, DTU 2012

3 Vortex induced vibrations 3/16 Validation Good agreement in the prediction of the lift slope, critical for aeroelastic damping characterization The double wake model Cl max Cd max v+,P-v+,P- v-,P+v-,P+ Cl min Cd max v-,P+v-,P+ v+,P-v+,P-

4 Vortex induced vibrations 4/16 PSD of CL PSD of CD about 10% shift in vortex shedding frequency PSD of CLPSD of CD Validation

5 Vortex induced vibrations 5/16 Forced vibration results

6 Vortex induced vibrations 6/16 (d) T*=10 (e) T*=11 (f) T*=13 Cl-x plot of A*/T*=0.03 series Forced vibration results

7 Vortex induced vibrations 7/16 V w u Structural model with 3 d.o.f. Aeroelastic simulations Typical blade section model

8 Vortex induced vibrations 8/16 Aeroelastic simulations eigenvalue stability analysis m=165 kg/m, f flap =0.7 hz, f edge =1.1 hz c=2.8 m (r/R=0.7), d=1.25% (  =0.2%) high damping of flap mode driven by high C D value flap mode edge mode damping of edge mode driven by negative slope of CL and CD value wind speed 25 m/s damping driving parameter

9 Vortex induced vibrations 9/16 Aeroelastic simulations eigenvalue stability analysis: reference to “reality” 3D aerodynamic characteristics m=165 kg/m, f flap =0.7 hz, f edge =1.1 hz c=2.8 m (r/R=0.7), d=1.25% (  =0.2%) edge mode wind speed 25 m/s damping driving parameter

10 Vortex induced vibrations 10/16 Aeroelastic simulations eigenvalue stability analysis – effect of mass and chord length wind speed 25 m/s C=2.8 C=1.6

11 Vortex induced vibrations 11/16 Aeroelastic simulations eigenvalue stability analysis – effect of structural properties m=165 kg/m, c=2.8 m: (Rf=0.021) wind speed 25 m/s structural pitch Edge frequency f flap =0.7 hz, f edge =1.1 hz

12 Vortex induced vibrations 12/16 Aeroelastic simulations non-linear aeroelastic stability analysis m=165 kg/m, c=2.8 m (Rf=0.021) wind speed 25 m/s f flap =0.7 hz, f edge =1.1 hz 10s excitation period at the frequency of the edge mode (1.1 hz) Strongly non linear behaviour. Difficult to measure damping aoa = 90 o

13 Vortex induced vibrations 13/16 Aeroelastic simulations non-linear aeroelastic stability analysis m=165 kg/m, c=2.8 m (Rf=0.021) wind speed 25 m/s f flap =0.7 hz, f edge =1.1 hz aoa = 100 o

14 Vortex induced vibrations 14/16 Aeroelastic simulations analysis of lock-in due to vortex shedding m=165 kg/m, c=2.8 m (Rf=0.021) f flap =0.7 hz, f edge =1.1 hz U=10 m/s U=15 m/s U=20 m/s f s1 =0.36hz f s2 =0.71hz f s1 =0.54hz f s2 =1.07hz f s1 =0.71hz f s2 =1.43hz

15 Vortex induced vibrations 15/16 Aeroelastic simulations analysis of lock-in due to vortex shedding m=165 kg/m, c=2.8 m (Rf=0.021) f flap =0.7 hz, f edge =1.1 hz U=25 m/s U=30 m/s U=35 m/s f s1 =0.89hz f s2 =1.79hz f s1 =1.07hz f s2 =2.14hz f s1 =1.25hz f s2 =2.50hz

16 Vortex induced vibrations 16/16 Conclusions The double wake model has been successfully applied The cut-off length acts as calibration parameter. Good results were obtained for relatively large values Lock-in was detected at the shedding frequency corresponding to T~10. The positive feedback between the lock-in phenomenon and the structural vibration is found to be the main reason for the vortex induced aero-elastic instability.

17 Vortex induced vibrations 17/16 Thanks for your attention END

18 Vortex induced vibrations 18/16 Aeroelastic simulations analysis of lock-in due to vortex shedding m=165 kg/m, c=2.8 m (Rf=0.021) f flap =0.7 hz, f edge =1.1 hz flapwise deflection flap deflection edgewise deflection


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