Mitigating Stall in Wind Turbines through Modified Leading-Edge Tubercle Airfoils

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Abstract
Tubercles at the leading edge (LE) of airfoils are used in maintaining the lift coefficient at the higher angle of attack (AoA) and delay stall. Previous research has documented the impact of varying the wavelength and amplitude of sinusoidal tubercles on the aerodynamic efficiency of various airfoil models, with a particular focus on changes at the leading edge. This study introduces a novel approach to tubercle design by analyzing the aerodynamic efficiency of a sinusoidal leading edge airfoil featuring a single, high-amplitude tubercle, offering a more realistic estimate of its effects. The research involves the development of three wing models – first, a baseline with a smooth leading edge; second, an airfoil with a tubercle labeled A3λ11; and third, an airfoil featuring a high-amplitude tubercle (A311λ11) on a sinusoidal leading edge. All airfoil models are developed using the NACA0021 airfoil profile and simulated at the 20° angle of attack. Large eddy simulations (LES) are conducted at a chord-based Reynolds number Rec = 1.2 × 105, and the results are validated against experimental data reported in the literature. Compared with the baseline airfoil, both tubercle airfoils show a substantial increase in the lift coefficient and a reduction in the drag coefficient. For the A3λ11 and A311λ11 airfoil models the lift coefficients increase by 34.8 and 12%, respectively. Moreover, reduction in the drag coefficient of about 10.3 and 23.6% are noticed for the A3λ11 and A311λ11 airfoil models, respectively. Additionally, the results reveal that the A311λ11 airfoil model exhibits a 14.9% reduction in the drag coefficient as compared to that of the sinusoidal A3λ11 airfoil model.

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