Numerical and wind tunnel investigation on aerodynamic coefficients of a three bladed Savonius wind turbine with and without overlap between blades

With the growing demand for energy worldwide, conventional sources are becoming more scarce and expensive. So there is an obvious need for alternative sources of energy. Wind is among the most popular and fastest growing sources of alternative energy in the world. It is an inexhaustible, indigenous resource, pollution-free, and available almost any time of the day, especially in coastal regions. Vertical axis wind turbines (VAWTs) include both a drag-type configuration, such as the Savonius rotor, and a lift-type configuration, such as the Darrieus rotor. The Savonius wind turbine is the simplest one. It is good at self-starting and works independently of wind direction. Its efficiency is relatively lower than that of the lift-type VAWTs. Nevertheless, this rotor is being used in different countries of the world because of its simple design, easy and cheap technology for construction and a good starting torque independent of wind direction at low wind speeds. Due to its simple design and low construction cost, this rotor is mainly used for water pumping and wind power on a small scale. The purpose of the project is to investigate the performance improvement of vertical-axis Savonius wind turbine. Wind tunnel investigation has been performed on semi-cylindrical three-bladed Savonius rotor scale models with different overlap ratios and without overlap within three blades. The experimental measurements and testing have been conducted in front of a low speed subsonic wind tunnel at different Reynolds number. Pressures around the concave and convex surfaces of each blades as well as the static torque for the rotor models are measured. Using these measured data aerodynamic characteristics, such as drag coefficients, static torque coefficient, and power coefficient have been calculated experimentally. The computational fluid dynamics (CFD) simulation has been performed to analyze the static rotor aerodynamics of those models. Commercial CFD software FLUENT and GAMBIT have been used for the computational simulation. Numerical and experimental results are compared for verification.