Effects of blade tapering on the performance of vertical axis wind turbines analysed through advanced visualization techniques

  • Martin Zahariev Dronamics Ltd, Sofia 1729, Bulgaria
  • Taimoor Asim School of Engineering, Robert Gordon University, Garthdee Road, Aberdeen, UK AB10 7GJ
  • Rakesh Mishra School of Computing and Engineering, University of Huddersfield, Queensgate, Huddersfield, UK HD1 3DH
  • Blaise Nsom Université de Bretagne Occidentale, IUT de Brest, IRDL UMR CNRS 6027, France
Keywords: Vertical Axis Wind Turbine, Computational Fluid Dynamics, Tip Speed Ratio, Torque Coefficient


Harnessing the wind energy effectively and efficiently, to fulfil the ever increasing energy demands, has long been an area of active research. This research study is aimed at exploring the blade design of a small-to-medium sized Savonius type Vertical Axis Wind Turbine (VAWT) for urban applications, as the published research in this area is severely limited. A commercial Computational Fluid Dynamics (CFD) based solver has been used to numerically simulate airflow around a conventional (cup-shaped) 2-bladed VAWT over a wide operational range (i.e. Tip Speed Ratio (TSR) from 0.4-1) in order to identify the peak performance point. Blade tapering has been shown to affect the performance of a wind turbine. As such, in the present study, three different VAWT configurations have been used with blade tapering corresponding to Delta, Rhomb and Cross shaped blades. It has been observed that tapering the blades of a Savonius VAWT significantly reduces the torque coefficient of the turbine, while there is a slight decrease in the power coefficient. Comparing the three tapered blade configurations, the delta blades depict higher performance than the competitor designs.


Hara, Y. Sumi, T. Wakimoto, M. Kogo, S. Mizuguchi, S. Yoshimi, K. and Akimoto, H. (2014). Comparison between symmetrical and cambered blade sections for small-scale wind turbines with low center of gravity. JSME Journal of Fluid Science and Technology. Volume: 9. 1 – 16.

Asim, T. Oliveira, A. Charlton, M. and Mishra, R. (2019). Improved Design of a Multi-Stage Continuous-Resistance Trim for minimum Energy Loss in Control Valves. Energy. Volume: 174. 954 – 971.

Asim, T. Oliveira, A. Charlton, M. and Mishra, R. (2019). Effects of the Geometrical Features of Flow Paths on the Flow Capacity of a Control Valve Trim. Petroleum science and Engineering. Volume: 172. 124 – 138.

Asim, T. Algadhi, A. and Mishra, R. (2018). Effect of Capsule Shape on Hydrodynamic Characteristics and Optimal Design of Hydraulic Capsule Pipelines. Journal of Petroleum Science and Engineering. Volume: 161. 390 – 408.

Asim, T. Charlton, M. and Mishra, R. (2017). CFD based Investigations for the Design of Severe Service Control Valves used in Energy Systems. Energy Conversion and Management. Volume: 153. 288 – 303.

Asim, T. and Mishra, R. (2017). Large Eddy Simulation based Analysis of Complex Flow Structures within the Volute of a Vaneless Centrifugal Pump. Sadhana. Volume: 42. 505 – 516.

Asim, T. and Mishra, R. (2016). Optimal design of hydraulic capsule pipelines transporting spherical capsules. Canadian Journal of Chemical Engineering. Volume: 94. 966 – 979.

Asim, T. and Mishra, R. (2016). Computational Fluid Dynamics based Optimal Design of Hydraulic Capsule Pipelines Transporting Cylindrical Capsules. International Journal of Powder Technology. Volume: 295. 180 – 201.

Asim, T. Mishra, R. Abushaala, S. and Jain, A. (2016). Development of a Design Methodology for Hydraulic Pipelines Carrying Rectangular Capsules. International Journal of Pressure Vessels and Piping. Volume: 146. 111 – 128.

Alexander, A.J. and Holownia, B.P. (1978). Wind Tunnel Test of a Savonius Rotor. Journal of Industrial Aerodynamics. Volume: 3. 343 – 351.

Mohamed, M.H.A. (2010). Design Optimization of Savonius and Wells Turbines, MSc thesis, University of Magdeburg, Germany.

Asim, T. Mishra, R. Ubbi, K. and Zala, K. (2013). Computational fluid dynamics based optimal design of vertical axis marine current turbines, Procedia CIRP. Volume: 11. 323 – 327.

Park, K. Asim, T. and Mishra, R. (2015). Numerical Investigations on the Effect of Blade Angles of a Vertical Axis Wind Turbine on its Performance Output. International Journal of COMADEM. Volume: 18. 3 – 10.

Fernando, M.S. (1987). On the Performance and Wake Aerodynamics of the Savonius Wind Turbine, PhD thesis, University of British Columbia, Canada.

Aldoss, T. and Kotb, M.A. (1991). Aerodynamic Loads on a Stationary Savonius Rotor. JSME International Journal. Volume: 34. 52 – 55.

Fujisawa, N. and Gotoh, F. (1992). Visualization study of the flow in and around a Savonius rotor. Experiments in Fluids. Volume: 12. 407 – 412.

Shahzad, A. Asim, T. Mishra, R. and Paris, A. (2013). Performance of a Vertical Axis Wind Turbine under Accelerating and Decelerating Flows. Procedia CIRP. Volume: 11. 311 – 316.

Asim, T., Mishra, R., Kaysthagir, S., and Aboufares, G., (2016), Performance Comparison of a Vertical Axis Wind Turbine using Commercial and Open Source Computational Fluid Dynamics based Codes in proc. International Conference on Jets, Wakes and Separated Flows, 16-18 June, Stockholm, Sweden.