Most of the wind turbines analysis studies have been conducted under steady and uniform wind conditions. The unsteady flow past rotating rotor blades is, however, one of the most challenging applications for a numerical simulation. This is attributed to the existing aerodynamic complexities under such conditions. In this paper, a numerical approach to investigate the global dynamic behaviour of a Darrieus turbine under unsteady and non-uniform flow conditions is proposed. The dynamic response of Darrieus wind turbine geared system operating in fluctuating inflow present a more significant challenge for this approach. In this work, unsteady Computational Fluid Dynamic simulation is used to investigate the aerodynamic performance. Using the validated numerical model, unsteady wind inflow performance that affects the aerodynamic performance and the bevel gear dynamic response is conducted. The present results show that the dynamic behaviour of the Darrieus turbine geared system is strongly affected by the fluctuating inlet velocity. As such, a change in the inlet velocity results in the entire response changing in both the aerodynamic performance and the dynamic vibration of the studied wind turbine. The study results will hopefully be of importance to wind industries that require designs of VAWTs operating in unsteady winds condition. (C) 2018 Elsevier Ltd. All rights reserved.