Performance assessment of Savonius wind turbine: Impact of the cylindrical deflectors with natural shapes

Savonius wind turbine, with various advantage features, is expanding its application for energy harvesting in urban and offshore environments. However, the drawback of this turbine relies on its relatively low aerodynamic efficiency. This study aims to enhance the Savonius wind turbine's aerodynamic performance to expand its effective application in urban areas and reduce offshore wind energy costs by using multiple cylindrical deflectors with natural geometry, changing from square to circular shapes. Results from the sequence of twodimensional (2D) unsteady computational fluid dynamics (CFD) simulations show various performances gained depending on the deflector shapes. The highest power coefficient, with an increment of up to 133% over the turbine without the deflectors without the complex structure and the requirement of the rotated cylinder, is attained with the square cylindrical one at different wind conditions. The insight flow analysis reveals that the high jet flow formed between the turbine and the deflectors is the physical reason behind such improvement, through adding more positive pressure force on the advancing blade while increasing the recovery pressure on the concave side of the returning one. The results suppose the significance of the present study with a simple wind turbine-deflector configuration for high energy harvesting in urban and offshore environments with effective costs.