Investigation on aerodynamics and active flow control of a vertical axis wind turbine with flapped airfoil
A 2D unsteady numerical simulation with dynamic and sliding meshing techniques was conducted to solve the flow around a threeblade Vertical axis wind turbine (VAWT). The circular wakes, strip-like wakes and the shedding vortex structures interact with each other result in an extremely unstable performance. An airfoil with a trailing edge flap, based on the NACA0012 airfoil, has been designed for VAWT to improve flow field around the turbine. Strategy of flap control is applied to regulate the flap angle. The results show that the flapped airfoil has an positive effect on damping trailing edge wake separation, deferring dynamic stall and reducing the oscillating amplitude. The circular wake vortices change into strip vortices during the pitch-up interval of the airfoils. Examination of the flow details around the rotating airfoil indicates that flap control improves the dynamic stall by diminishing the trend of flow separation. Airfoil stall separation has been suppressed since the range of nominal angle of attack is narrowed down by an oscillating flap. Vortices with large intensity over rotational region are reduced by 90 %. The lift coefficient hysteresis loop of flapped airfoil acts as an O type, which represents a more stable unsteady performance. With flap control, the peak of power coefficient has increased by 10 % relative to the full blade VAWT. Obviously, the proposed flapped airfoil design combined with the active flow control significantly has shown the potential to eliminate dynamic stall and improve the aerodynamic performance and operation stability of VAWT.
KeywordsAerodynamics Control strategy Flapped airfoil Vertical axis wind turbine (VAWT)
Unable to display preview. Download preview PDF.
- C. K. Maucher, B. A. Grohmann, P. Danker, A. Altmikus, F. Jensen and H. Baier, Actuator design for the active trailing edge of a helicopter rotor blade, Proceedings of the 33rd European Rotorcraft Forum, Kazan, Russia (2007) 11–13.Google Scholar
- A. Mishra, J. Sitaraman, J. D. Baeder and D. G. Opoku, Computational investigation of trailing edge flap for control of vibration, The 25th AIAA Applied Aerodynamics Conference, Miami, Florida, USA (2007) 1–25.Google Scholar
- T. K. Barlas and G. V. Kuik, Aeroelastic modelling and comparison of advanced active flap control concepts for load reduction on the upwind 5MW wind turbine, Proceedings of the 2009 European Wind Energy conference & Exhibition, Marseille, French (2009) 1–12.Google Scholar
- I. Abdallah, Advanced load alleviation for wind turbines using adaptive trailing edge flaps: sensoring and control, Denmark Technical University, Roskilde, Denmark (2010).Google Scholar
- W. J. Zhu, W. Z. Shen and J. N. Serrensen, Modeling of airfoil trailing edge flap with immersed boundary method, The 2011 International Conference on Offshore Wind Energy and Ocean Energy, Beijing, China (2011) 1–9.Google Scholar
- T. Lutz, A. Wolf, W. Wiirz and J. G. Jeremiasz, Design and verification of an airfoil with trailing edge flap and unsteady wind tunnel tests, UPWIND Technical Report, Stuttgart, Germany (2011).Google Scholar
- G. K. Tan, G. X. Shen and W. H. Su, Experimental investigation on the aft-element flapping of a two-element airfoil at high attack angle, J. of Experiments in Fluid Mechanics, 21 (3) (2007) 1–7.Google Scholar
- I. Paraschivoiu, Wind turbine design: with emphasis on darrieus concept, Polytechnic International Press, Montreal, Canada (2002).Google Scholar
- J. C. Hunt, A. A Wray and P. Moin, Eddies stream and convergence zones in turbulent flows, Proceedings of the 1988 Summer Program, California, USA (1998) 193–208.Google Scholar