Power augmentation of Darrieus wind turbine blades using trapped vortex cavity

Abstract

Enhancing the performance of Darrieus Vertical Axis Wind Turbines (VAWTs) is the key to boost their possible commercialisation in the yet highly competitive wind energy market. This study evaluates an active boundary layer control technique to increase the aerodynamic efficiency of Darrieus VAWTs. A cavity is created on the airfoil's suction side, where suction is applied to create a trapped vortex. High-fidelity Computational Fluid Dynamics (CFD) simulations are used after validation against experimental results. The effect of suction momentum ratio Cμ on the performance of the turbine is investigated. The turbine with suction cavity airfoils (SC) shows a higher power coefficient than the one with baseline airfoil (BL) blades, especially at low tip-speed ratios. For the selected test case, the net maximum predicted power coefficient is 0.435 for the SC turbine at TSR = 2.3, 0.375 for the baseline at TSR = 2.6. At the lower tip-speed ratios, i.e. TSR = 2, the power coefficient of the SC turbine is almost double that of the BL turbine. The feasibility of the active control technique is finally discussed, demonstrating its potential as an effective solution for the performance augmentation of the Darrieus turbine.