Studies on the performance of Savonius rotors in a numerical wave tank

Waves were generated in a numerical wave tank (NWT) using a piston type wave-maker. Firstly, the performance of a 1.8 m diameter Savonius rotor was tested at a mean wave height (H) and a mean wave period (T) of 2.00 m and 12.68 s respectively. The Savonius rotor performed the best at a submergence depth of 1.0 D when compared to greater depths. The power produced by the rotor decreased by 37% at 1.25 D compared to 1.0 D. In addition to this, the blade entry angle also affected the rotor performance. The 20° rotor at 42.5 rpm was found to have the best performance. The maximum power and efficiency at the mean sea state were 15.01 kW and 16.7% respectively. Secondly, simulations were performed at the minimum sea state (H = 1.37 m, T = 10.00 s) and the maximum sea state (H = 2.34 m, T = 14.39 s). It is observed that the peak power at the maximum sea state is lower than the peak power at the mean sea state. The maximum power that the rotor produced was 15.01 kW at 42.5 rpm which gave an efficiency of 16.7% at the mean sea state.