Numerical Simulation of Savonius Vertical Axis Wind Turbine and Evaluation of the Effect of Horizontal Overlap Parameter on its Performance

Among renewable energies, wind energy is considered as the least costly source of available energy. Savonius wind turbine is a vertical axis wind turbine type which its performance is not dependent on wind direction. In this paper, the effect of overlap ratios in the common semi-cylindrical Savonius wind turbine is investigated with a new attitude. In this regard, positive and negative overlap ratios are considered by maintaining the rotor diameter. Numerical modeling is conducted using Ansys-Fluent commercial software and sliding mesh method. Simulations are carried out by using RANS method and Realizable K-ε turbulence model. By examining the velocity contours around the blades in different overlap ratios, it is found that the perturbation is higher in the circumference of the blades with negative overlap ratios. This reduces the useful net momentum. Moreover, according to the torque and power coefficients, it is found that in general, geometry with an overlap ratio of 0.15 could be more appropriate