Enhancing aerodynamic performance of vertical axis wind turbines using bionic airfoils inspired by swordfish tail

Abstract

In this work, a pioneering approach is proposed to enhance the efficacy of vertical axis wind turbines within the aerodynamic field. This innovative method involves integrating a bionic airfoil, inspired by the tail fin of a swordfish, along the trailing edge of the airfoil. To evaluate the impact of these biomimetic airfoils on wind turbine functionality, applications such as numerical simulations facilitated by computational fluid dynamics (CFD) and design of experiments (DOE) were employed. The primary objective of this study is to mitigate the flow separation phenomenon that occurs when wind turbines operate at low tip speed ratios (TSR < 4). The results indicate that the addition of the bionic tail delays the angle at which the peak torque appears, and enhances positive torque generation effectively within the phase angle range of 60° to 150°, suggesting successful suppression of the flow separation phenomenon. The presence of the tail also postpones the occurrence of dynamic stall, particularly near the trailing edge of the airfoil, and reduces losses associated with the expansion and shedding of dynamic stall vortices. As the tip speed ratio increases, the average power coefficient of the bionic airfoil exhibits a positive trend. Notably, at a tip speed ratio of 2.63, a significant increase in the average power coefficient of approximately 17% was observed. The analysis of the downstream wake of the wind turbine reveals that the bionic tail enhances the speed loss in the wake. This indicates that the blades can generate greater lift at a lower tip speed ratio, allowing the vertical axis wind turbine to operate effectively at low wind speeds, particularly in urban areas with significant development potential.