Numerical study of detailed flow field and performance of Savonius wind turbines

The Savonius vertical axis wind turbine is simple in structure, has good starting characteristics, relatively low operating speeds, and an ability to accept wind from any direction, although it has a lower efficiency than some other vertical axis wind turbines. So far a number of experimental investigations have been carried out to study the performance of the Savonius rotor; however, there is a lack of detailed descriptions of the flow field for different types of Savonius rotors. The aim of this paper is to numerically explore the non-linear two-dimensional unsteady flow over a conventional Savonius-type rotor and a Bach-type rotor, and develop a simulation method for predicting their aerodynamic performance. The simulations are performed using Star-CCM+. The motion of the blades is solved by using a moving mesh. A comparative study of the two types of rotors was carried out, and numerical simulation results were compared with experimental data. The Bach-type rotor is demonstrated to have better performance for torque and power coefficient than the conventional Savonius-type rotor. A discussion of the causes of these differences is presented that is based on a detailed study of the respective flow field characteristics, including the behavior of moment coefficients, velocity vectors and pressure distribution. A simulation method for further study of new blades shapes is suggested.