Impact of Negative Camber for Performance of Vertical Axis Wind Turbine

Abstract

Vertical axis wind turbines are often best suited for urban areas with limited space and turbulent wind flows. This study examined the impact of airfoil shape on the performance of an H-Darrieus wind turbine using Computational Fluid Dynamics (CFD) modeling. As wake and blade interactions are significant for VAWTs, an unsteady simulation with a sliding mesh was used for all simulations. The models show that achieving a quasi-steady state solution for the VAWT requires at least 50 revolutions to fully account for the unsteady wake interactions with the blades. The CFD results confirmed that a negatively cambered airfoil does not improve the overall efficiency or power coefficient of a VAWT compared to a symmetric or positively cambered airfoil section. The analysis shows that in the first half of the VAWT cycle, the turbine with a negatively cambered airfoil produces an average torque that is 8.8% higher. However, in the second half of the cycle, the turbine with a positively cambered airfoil generates an average negative torque that is 118% lower. As a result, it is recommended to use an adaptive cambered airfoil profile that can optimize performance over the entire cycle.