Application of overset mesh approach in the investigation of the Savonius wind turbines with rigid and deformable blades

Machines utilising renewable energy constantly undergo research aimed at raising their efficiency. One of them is a Savonius wind turbine, where scientists propose adjustments to improve its aerodynamic properties. At present, their assessment is usually performed by means of transient computational fluid dynamics simulations with two- or threedimensional models. In this paper, the overset (chimera) mesh approach was applied to investigate the performance of a Savonius wind turbine equipped with deformable blades. They were continuously deformed during rotation by a dedicated mechanism to increase a positive torque of the advancing blade, and meanwhile, decrease a negative torque of the returning blade. A quasi-two-dimensional model with a two-way fluid-structure interaction method was applied, where the structural solver determined blade deflection caused by the predefined deformation mechanism and aerodynamic loads, whereas the coupled computational fluid dynamics solver determined the transient flow. The deformable blades rotor performance was calculated and compared with a conventional rigid Savonius turbine, both simulated using the overset mesh approach. The average value of the power coefficient achieved a 55% rise in the case of deformable blades turbine. Additionally, to validate the overset method, its results were compared with the classical sliding mesh method for a conventional rigid rotor.