Performance of Savonius Turbines with Tubercles Inspired by Humpback Whales

Recent studies found that tubercles had been integrated into various applications beyond nature to enhance performance. Therefore, the present work investigates the performance of a Savonius turbine with various tubercle configurations at a wind speed of 7 m/s which corresponds to a Reynolds number of 148,000. The Savonius turbines with tubercle features were initially designed and inspired by the distribution of tubercles on the flippers of humpback whales. However, only the models with the best performance were chosen for fabrication and tested in the wind tunnel. The new turbine designs have 33% of the blade without tubercles, with turbine model 1 (D1) having a large tubercle beginning in the midspan and tapering towards the endplates, while turbine model 2 (D3) applies the 33% without tubercles in the midspan of the blade. The results demonstrated that turbine model 1 had the highest maximum Cp of 0.19 at the tip speed ratio of 0.78 and indicated that the spanwise location of tubercles in which it is integrated into the turbine is a significant geometric arrangement to improve the performance. The new turbine models designed with tubercles performed significantly better than the baseline model, with 46.15% and 23.08% improvements, respectively. The flow visualization for both models with tubercle configurations showed smaller wake sizes that represent reduced drag and eventually produced higher performance in comparison with the baseline. The results provide insights into the implementation of the tubercles concept on a Savonius turbine with a low aspect ratio.