Sensitivity of Vertical Axis Wind Turbines to Rotor Shape and Blade Design: A Computational Investigation

In this paper we present a computational investigation of the aerodynamics and performance of four vertical axis wind turbines, comparing two different troposkein rotors equipped with two different airfoil sections. Simulations were performed by resorting to an experimentally-validated 2D/3D unsteady Computational Fluid Dynamics model, based on the U-RANS formulation of the equation and relying upon the k − ω SST turbulence model in low-Reynolds formulation. The performance of the selected wind turbine configurations are investigated and discussed considering different operating conditions at 2D level, and then focusing on the peak efficiency condition for the fully 3D analysis. Overall power coefficient data and trends, spanwise distributions and local blade aerodynamics are used to discuss the impact of rotor solidity, Reynolds number, and airfoil shape on turbine performance. The investigation reveals that the adoption of non-symmetric laminar profiles provides important advantages in complex flow regions, typical of such class of machines, both in the equatorial sections and along the span. Moreover, a solidity formulation based on the equatorial section turns out to be representative of the aerodynamics of the entire turbine, despite the trospokein shape of the rotor.