Abstract
Vertical axis wind turbine blades undergo dynamic stall due to the large angle of attack variation they experience during a turbine rotation. The flow over a single blade was modeled using a sinusoidally pitching and surging airfoil in a non-rotating frame with a constant freestream flow at a mean chord Reynolds number of \({10^5}\). Two-dimensional, time-resolved velocity fields were acquired using particle image velocimetry. Vorticity contours were used to visualize shear layer and vortex activity. A low-order model of dynamic stall was developed using dynamic mode decomposition, from which primary and secondary dynamic separation modes were identified. The interaction between these two modes was able to capture the physics of dynamic stall and as such can be extended to other turbine configurations and problems in unsteady aerodynamics. Results from the linear pitch/surge frame are extrapolated to the rotating VAWT frame to investigate the behavior of identified flow structures.
Similar content being viewed by others
Abbreviations
- t :
-
Time (s)
- \(\alpha\) :
-
Angle of attack (°)
- \(\theta\) :
-
Turbine rotation angle (°)
- \(Re_{\rm c}\) :
-
Chord Reynolds number (\(\frac{Uc}{\nu }\))
- \(U_\infty\) :
-
Wind speed (\(\hbox {m s}^{-1}\))
- U :
-
Effective velocity (\(\hbox {m s}^{-1}\))
- \(\bar{U}\) :
-
Average velocity in experiment (tunnel velocity) (\(\hbox {m s}^{-1}\))
- \(\chi\) :
-
Spanwise vorticity (\(\hbox {s}^{-1}\))
- \(\eta\) :
-
Tip speed ratio (\(\frac{\omega R}{U_\infty }\))
- \(\omega\) :
-
Turbine frequency (\(\hbox {rad s}^{-1}\))
- \(\varOmega\) :
-
Pitch/surge frequency (\(\hbox {rad s}^{-1}\))
- R :
-
Turbine radius (m)
- Ro :
-
Rossby number (\(\frac{U_\infty }{2c \omega }\))
- c :
-
Chord length (cm)
- \(\nu\) :
-
Kinematic viscosity (\(\hbox {m}^2\hbox { s}^{-1}\))
- \(\lambda\) :
-
Transformed DMD eigenvalues (\(\hbox {rad s}^{-1}\))
- k :
-
Reduced frequency (\(\frac{\varOmega c}{2 \bar{U}}\))
- \(\varGamma _1\) :
-
Vortex center criteria
- \(\varGamma _2\) :
-
Vortex boundary criteria
- \(x,\, u\) :
-
Streamwise coordinate [c], streamwise velocity (\(\hbox {m s}^{-1}\))
- \(y,\, v\) :
-
Cross-stream coordinate [c], cross-stream velocity (\(\hbox {m s}^{-1}\))
- z :
-
Spanwise coordinate (c)
- xl :
-
Leading edge position (c)
- i :
-
Imaginary component
- r :
-
Real component
- j :
-
Variable index
- \(\pm\) :
-
Pitch up (+) and down (−)
References
Baik YS, Bernal LP, Granlund K, Ol MV (2012) Unsteady force generation and vortex dynamics of pitching and plunging aerofoils. J Fluid Mech 709:37–68
Brent S (2009) AWEA standard update
Carr L, McAlister K, McCroskey W (1977) Analysis of the development of dynamic stall based on oscillating airfoil experiments. Technical Report January, NASA
Carr LW (1988) Progress in analysis and prediction of dynamic stall. J Aircr 25(1):6–17
Chakraborty P, Balachandar S, Adrian RJ (2005) On the relationships between local vortex identification schemes. J Fluid Mech 535:189–214
Chen KK, Tu JH, Rowley CW (2012) Variants of dynamic mode decomposition: boundary condition, Koopman, and Fourier analyses. J Nonlinear Sci 22(6):887–915
Choi J, Colonius T, Williams DR (2015) Surging and plunging oscillations of an airfoil at low Reynolds number. J Fluid Mech 763:237–253
Dabiri JO (2011) Potential order-of-magnitude enhancement of wind farm power density via counter-rotating vertical-axis wind turbine arrays. J Renew Sustain Energy 3(4)
Gerakopulos R (2010) Aerodynamic characterization of a NACA 0018 airfoil at low Reynolds numbers. In: 40th AIAA fluid dynamics conference, July. Chicago, IL
Graftieaux L (2001) Combining PIV, POD and vortex identification algorithms for the study of unsteady turbulent swirling flows. Meas Sci 1422
Greenblatt D, Harav AB, Mueller-Vahl H (2013) Mechanism of dynamic stall control on a vertical axis wind turbine. 51st AIAA aerospace sciences meeting
Hau E (2013) Wind turbines: fundamentals, technologies, application, economics. Springer, Berlin
Islam M, Ting DSK, Fartaj A (2007) Desirable airfoil features for smaller-capacity straight-bladed VAWT. Wind Eng 31(3):165–196
Jones AR, Babinsky H (2010) Unsteady lift generation on rotating wings at low Reynolds number. J Aircr 47(3):1013–1021
Kinzel M, Mulligan Q, Dabiri JO (2012) Energy exchange in an array of vertical-axis wind turbines. J Turbul 13(38):1–13
Mulleners K, Raffel M (2012) The onset of dynamic stall revisited. Exp Fluids 52(3):779–793
Mulleners K, Raffel M (2013) Dynamic stall development. Exp Fluids 54(2):1469–1477
Müller-Vahl HF, Strangfeld C, Nayeri CN, Paschereit CO, Greenblatt D (2015) Control of thick airfoil, deep dynamic stall using steady blowing. AIAA J 53(2):277–295
Prangemeier T, Rival D, Tropea C (2010) The manipulation of trailing-edge vortices for an airfoil in plunging motion. J Fluids Struct 26(2):193–204
Rowley CW, Mezić I, Bagheri S, Schlatter P, Henningson DS (2009) Spectral analysis of nonlinear flows. J Fluid Mech 641:115–127
Schmid PJ (2010) Dynamic mode decomposition of numerical and experimental data. J Fluid Mech 656:5–28
Simão Ferreira C, Bijl H, van Bussel G, van Kuik G (2007a) Simulating dynamic stall in a 2D VAWT: Modeling strategy, verification and validation with particle image velocimetry data. J Phys Conf Ser 73
Simão Ferreira C, van Bussel G, Scarano F, van Kuik G (2007b) 2D PIV visualization of dynamic stall on a vertical axis wind turbine. In: 45th AIAA Aerospace science meeting
Simão Ferreira C, van Kuik G, van Bussel G, Scarano F (2009) Visualization by PIV of dynamic stall on a vertical axis wind turbine. Exp Fluids 46(1):97–108
Simão Ferreira CJ, Van Zuijlen A, Bijl H, van Bussel G, van Kuik G (2010) Simulating dynamic stall in a two-dimensional vertical axis wind turbine: verification and validation with particle image velocimetry data. Wind Energy 13:1–17
Tsai HC, Colonius T (2014) Coriolis effect on dynamic stall in vertical axis wind turbine at moderate Reynolds number. In: 32nd AIAA applied aerodynamics conference, Atlanta, GA
US Energy Information Administration (2012) Electric power monthly. Technical Report DOE/EIA-0226, US energy information administration
Windspire (2013) Standard wind unit 1.2kw. Accessed 11/2013
Acknowledgments
This work was supported by the Gordon and Betty Moore Foundation through grant GBMF#2645 to the California Institute of Technology. The authors thank Professor Peter Schmid for his assistance in implementing the dynamic mode decomposition algorithm, Professor Morteza Gharib for the use of the free surface water channel facility, Hsieh-Chen Tsai and Professor Tim Colonius for discussion on the Coriolis effect and Professor John Dabiri for his insight from VAWT field research.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Additional information
This article belongs to a Topical Collection of articles entitled Extreme Flow Workshop 2014. Guest editors: I. Marusic and B. J. McKeon.
Rights and permissions
About this article
Cite this article
Dunne, R., McKeon, B.J. Dynamic stall on a pitching and surging airfoil. Exp Fluids 56, 157 (2015). https://doi.org/10.1007/s00348-015-2028-1
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/s00348-015-2028-1