Computational fluid dynamics and turbulence modelling in various blades of Savonius turbines for wind and hydro energy: Progress and perspectives

The world's focus is shifting towards solar and wind energies which are primarily contributing to renewable energy. Wind turbines are subdivided into horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs). Savonius turbine is a VAWT that works mainly on the drag force. Despite its low efficiency, a Savonius turbine is quite useful due to its operational independence on wind direction, its advantage as a stand-alone turbine, and its low-cost power production. Savonius turbine performance depends mainly on the overlap ratio, aspect ratio, number of blades, and blade design. Various researchers have focused on modifying these parameters to improve the efficiency of Savonius turbines using CFD studies. One key challenge encountered in such studies is the selection of an appropriate turbulence model to predict the flow characteristics and performance parameters accurately. Due to small computational time and cost associated with the RANS-based turbulence models, various researchers have focused mainly on using these models. This article presents a review of various turbulence models employed in different CFD studies on Savonius turbines. Further, various computational approaches used in CFD simulations of Savonius wind and hydro turbines and key findings of such studies are also presented along with future directions. •Steps for CFD simulations of Savonius wind turbines presented.•Effects of turbulence models on Savonius turbine characteristics are explored.•Grid requirements, computing costs, and accuracies of turbulence models are shown.•Use of different turbulence models for various blade shapes is reviewed.•Future scope of CFD studies presented.