In this work, the performances of several different design configurations for Savonius turbines are investigated with the numerical approach. To compare different design configurations, 2D simulations were carried out in the ANSYS Fluent v15.0.k-ω SST model and the Spalart-Allmaras model for low TSR simulation was selected as the turbulence model for the simulations. The results are validated with experimental data before the simulations are carried out. The overlap ratio for spline-shape Savonius rotor blade are investigated for two different wind speeds (3m/s and 7m/s), and the optimal overlap ratio for certain wind speed is determined. Then several simple drag-reducing augmentations, including holes, venting slots, and slats at blade tips are investigated. Through numerical study, the impact of venting slot/holes to the Savonius rotor is understood. Based on the test results of drag-reducing profiles and inspired by the concept of cyclorotor, a new design of a self-regulating Savonius rotor is proposed. The blade tip arrangement of the new design is similar to an H-rotor and can change its angle around its own axis through a linkage system. The blade tip will bend inward opening a gap for the returning blade to reduce the negative torque from the returning blade, and bend outward, closing the gap for the advancing blade. Two different designs for blade tip are investigated and compared. Finally, the static torque performances of three different designs of the Savonius rotor, including the self-regulating rotor, are investigated. Comparing the static torque performance and dynamic torque performance not only helps to find the design with the best self-starting ability, but also gives a better insight into the torque mechanism of the Savonius rotor.