In the last few decades vertical axis wind turbines (VAWTs) have gained increased interest among researchers worldwide. This paper aims to present full two-way Fluid Structure Interaction (FSI) approach to model operation of the Savonius-type VAWT. The developed methodology couples the set of Unsteady Reynolds Averaged Navier-Stokes Equations (URANS) with the unsteady linear elasticity equations and dynamic mesh approach to comprehensively describe the deformations of the turbine rotor. The obtained results provide detailed information on the unsteady flow fields around the operating wind turbine as well as deformations of a turbine rotor caused by an interaction between solid and flowing air. This allowed us to determine the influence of the unsteady deformations of a turbine rotor on the instantaneous and average performance of a wind turbine. Computations were carried out for the wind speed equal to 15 m/s and the tip speed ratio equal to 0.8. The simulations were performed using the commercial ANSYS software. The obtained results showed that deformation of the turbine rotor increases the wind turbine power coefficient by around 5%. Moreover, it was shown that the centrifugal force has a significant effect on the rotor deformation and turbine operation, hence it cannot be neglected. (c) 2020 Published by Elsevier Ltd.