Aerodynamic performance of helical Savonius wind rotors with 30° and 45° twist angles: Experimental and numerical studies

Abstract

In this study, the aerodynamic performance of helical Savonius rotors with 30° and 45° twist angles have been investigated experimentally and numerically and compared with the conventional rotor with zero twist. This comparison has been performed at two Reynolds number of 1.50 × 105 and 1.84 × 105 (corresponding to wind velocities of 7.3 and 9 m/s) on Savonius type rotors with an aspect ratio of 1.0. Numerical simulations have been performed using the ANSYS-Fluent commercial software using the sliding-mesh method for considering the rotation of the turbine. The experimental measurements, however, are performed at an open-circuit wind tunnel facility. Results show that the maximum power coefficient of the helical rotors are less than the conventional rotor, in a manner that this coefficient decreases from 0.12 to 0.11, when the conventional rotor is replaced with the helical rotor having 45° twist angle. However, the helical rotors have a more uniform time variations of the torque coefficient. The maximum power coefficient for all the rotors has occurred at the tip speed ratio of 0.7. The good agreement observed between the numerical and experimental results revealed the suitability of the employed numerical scheme for predicting the aerodynamic performance of Savonius-type wind turbines.