Investigation on the Aerodynamic Performance of a Vertical Axis Wind Turbine

Abstract

The two dimensional unsteady flow around a vertical axis wind turbine (VAWT) comprising three rotating symmetric airfoils (NACA0018) was studied numerically with the consideration of the near wake. The simulations were set to run at several tip speed ratios (TSR) ranging from 1 to 5 and then the variation of the power coefficient (Cp) was calculated as a function of TSR. The maximum Cp was reported as 0.34 at TSR of 3.8. Furthermore, the influence of the rotor diameter on the aerodynamic performance of the VAWT was investigated for the same chord-length-to-rotor- radius ratio. The results show that Cp remains almost constant at the same value of TSR for different rotor diameters. The Cp for the case of a low Reynolds number flow within the turbine was low due to the presence of leading edge separation bubble and reduction in lift-to-drag ratio. Finally, the effect of the solidity ratio on the Cp was studied and it was found that the maximum Cp could be achieved at relatively lower value of TSR with the increase in the solidity ratio.