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The VAWT in Skew: Stereo-PIV and Vortex Modeling

The VAWT in Skew: Stereo-PIV and Vortex Modeling. ir. C.J. Sim ã o Ferreira, M.Sc. K. Dixon, Dipl.-Ing. C. Hofemann, Prof. Dr. ir. G.J.W. van Bussel, Prof. Dr. ir. G. A.M. van Kuik 47th AIAA Aerospace Sciences Meeting 5 - 8 Jan 2009, Orlando World Center Marriott Orlando, Florida. Who

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The VAWT in Skew: Stereo-PIV and Vortex Modeling

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  1. The VAWT in Skew: Stereo-PIV and Vortex Modeling ir. C.J. Simão Ferreira, M.Sc. K. Dixon, Dipl.-Ing. C. Hofemann, Prof. Dr. ir. G.J.W. van Bussel, Prof. Dr. ir. G. A.M. van Kuik 47th AIAA Aerospace Sciences Meeting 5 - 8 Jan 2009, Orlando World Center Marriott Orlando, Florida

  2. Who What Why How Where Results Table of contents Carlos, Kristian, Claudia, ... Vertical Axis Wind Turbine (VAWT) To understand the influence of the skew angle on the performance of the VAWT Numerical & Experimental… Upwind & Downwind blade passage Effect of the skewed angle on wake

  3. What ?VAWT

  4. What VAWT in Skew Skewed flow -> Misalignment of the flow perpendicular to the ground

  5. Why ? VAWT operating under skewed flow show a higher efficiency than VAWT operating under normal conditions ! Why ?

  6. How ?Numerical 3D unsteady free wake panel method • Design and research tool • capturing the 3D nature of a VAWT and its wake • Allows to analyze the effect of skew in terms of • bound circulation, • shed and trailing vorticity • torque, wake and flow asymmetry • Validated by PIV and Smoke Trail Studies

  7. How? Numerical

  8. How ?Experimental Two blades: NACA 0015 (trailing edge) NACA 0018 (quarter chord) Tip speed ratio: λ = 4 Wind speed: 10 m/s Reynolds number: 8 x 10 4 • c = 60 mm • l = 700 mm Z Y X • d= 570 mm λ = ωR/V

  9. How? Low speed /Low turbulence Wind Tunnel Wind X Z Y

  10. How ? 3D-Stereo-PIV

  11. Where ? Upwind & Downwind NumericalUpwind & Downwind Experimental Downwind 180° Y measuring planes 120 mm 0.42 y/R 90° wind X -120 mm -0.42 y/R downwind upwind 0°

  12. Results ? Tip vortex locus (Exp.) • Skewangles: • = +20 = 0  = - 20

  13. Results ? Tip vortex locus (Sim.) • Skewangles: • = +20 = 0  = - 20

  14. Results ? Tip vortex locus

  15. Results ? Location of the wake • Azimuth angle: • = 90 • Skew angles: •  = +20 •  = 0 •  = - 20

  16. Results ? Trailing vorticity • Skew angles: •  = +20 •  = 0 •  = - 20

  17. Results ? Shed vorticity • Skew angles: •  = +20 •  = 0 •  = - 20 18

  18. Results ? Bound vorticity • Skew angles: •  = +20 •  = 0 •  = - 20 19

  19. Results ? Normal Force • Skew angles: •  = +20  •  = 0 20

  20. Results ? Trailing vorticity • Skew angles: •  = 0 •  = 10 •  = 20 •  = 30 21

  21. Results ? Shed vorticity • Skew angles: •  = 0 •  = 10 •  = 20 •  = 30 22

  22. Results ? Tangential Force • Skew angles: •  = 0 •  = 10 •  = 20 •  = 30 23

  23. Results ? Validation 24

  24. Conclusions ? The impact of the skew angle on the wake has been shown by the 3D panel method Skewed flow increases the performance of the VAWT generates an asymmetry of the wake in z-direction causes asymmetry of the expansion of the wake in y-direction 3D unsteady free wake panel code is able to replicate the effect of skew shows the impact of the skew angle on the strength of the wake for trailing and shed vorticity shows the effect on bound vorticty as well as on normal and tangential forces is not able to capture the roll of motion

  25. Questions ?

  26. Results ? Induction in x-direction • Skew angles: •  = +20  •  = 0 •  = - 20

  27. Results ? Induction in z-direction • Skew angles: •  = +20  •  = 0 •  = - 20 28

  28. Why ?

  29. Δt How ? Stereo PIV / Displacement

  30. NACA 0018: leading edge quarter chord NACA 0015: flat tip trailing edge What ? Blade configuration

  31. Where ? Wind Y Z X

  32. Where ? 180° Y measuring planes rotational directions 180 mm 120 mm 60 mm 90° wind X -60 mm -120 mm -180 mm downwind upwind 0°

  33. How? StereoPIV Method: indirect monitoring due to tracer particles the displacement is pictured via two images, taken within Δt Stereo -> 2 cameras (rotated) to quantify the out of plain motions Laser z x y Z Y X

  34. How? DataReduction

  35. How ?Evaluation • Methode: • longest vorticty level • Integration over the enclosed area

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