Numerical simulation and research on improving aerodynamic performance of vertical axis wind turbine by co-flow jet

The co-flow jet (CFJ) based active flow control method is a new approach for suppressing the flow separation on the blade, delaying the stall, and enhancing the lift. In this study, a detailed numerical analysis of the flow field developing around a Darrieus wind rotor equipped with CFJ is presented in order to explore the effectiveness of CFJ in the efficiency improvement of vertical axis wind turbines (VAWTs). Unsteady Computational Fluid Dynamics simulations of the straight one-bladed and three-bladed rotors with the NACA0015 profile, using the shear stress transport (SST) k-ω turbulence model, were conducted. As a result, the effects of jet operational parameters such as the injection site and the momentum coefficient on the aerodynamic performance of the straight-bladed Darrieus vertical axis wind turbine (VAWT) have been comprehensively studied. The numerical results suggest that CFJ would be capable of recovering some of the power loss due to blade stall and its control effectiveness is more pronounced with the increase in the jet momentum coefficient. In addition, a power saving method for intermittent injection of a CFJ in accordance with the cyclic variation of the angle of attack is proposed and our results show that the stalling characteristics around a VAWT blade especially at low tip speed ratios can be considerably improved using intermittent CFJ which requires much less additional energy input.