Performance characterization of a slotted wind turbine airfoil featuring passive blowing

Abstract

Renewable energy is crucial for a sustainable future, and wind energy holds significant potential as a viable solution to meet global demands. The current study employs high-fidelity Computational Fluid Dynamics (CFD) simulations to investigate the unsteady aerodynamics of an S809 wind turbine airfoil carved with an inclined contracting curved slot at the mid-chord location. The numerical analyses cover a wide range of angles of attack, α = 0°− 20°, at a chord-based Reynolds number of Rec = 5 × 105. The slotted airfoil exhibits superior aerodynamic performance over moderate-to-high angles of attack (α > 6°), with increased lift, reduced drag, and enhanced glide ratio of up to 1.3×, 0.5×, and 3.7× respectively, compared to the baseline. The slot-induced flow control significantly suppresses flow transition and separation across the airfoil surfaces. The attached-flow regime impedes the formation of flow anomalies, resulting in enhanced aerodynamic performance. Comparative analyses reveal significant reductions in velocity fluctuations, Reynolds shear, vorticity, and turbulent kinetic energy, across the slotted airfoil surface and wake region. The aeroacoustic analysis of the slotted airfoil exhibits substantial reduction in the far-field noise over moderate-high angles of attack, with an overall noise level reduction of approximately 14 decibels recorded at α = 17°. Overall, this study highlights the potential of slot-induced flow control as an effective strategy for enhancing the aerodynamic performance of wind turbines.

Keywords

• Flow-control
• Reynolds shear
• Turbulent kinetic energy
• Strain rate
• Far-field noise