Abstract The performance of a Savonius wind turbine with constant cross-sections is examined by means of quasi 2D flow predictions executed in ANSYS CFX. Simulations were performed in a way that allows comparison with wind tunnel data presented in a related paper, where two designs were simulated: the Classical and so-called Bach-type Savonius rotor. Comparison revealed the importance of applying a laminar–turbulent transition model. Additionally, turbine design with an Elliptical blade shape was modelled. Such a shape has not been examined before with the use of CFD. All mentioned designs were analysed at different values of tip speed ratio. The paper presents a systematic analysis of the obtained coefficients of power, coefficients of torque and torque variation with the angle of incidence. The most characteristic flow structures are identified and compared. Finally, the wake is observed and examined by means of FFT analysis of pressure fluctuations at the point located downstream of the rotor.