Bio-inspired asymmetric airfoil design based on the wind energy quality and flow field spatio-temporal on the vertical axis wind turbine rotor plane

Significant progress has been made in optimizing the energy efficiency of vertical-axis wind turbines (VAWTs). However, most optimization studies overlooked the variation in wind energy quality between the upwind and downwind regions. This oversight may hinder further improvement in wind energy utilization. Adopting a typical H-type VAWT, this study evaluates the wind energy quality in the VAWT rotor plane. Lagrangian coherent structure and dynamic mode decomposition are employed to investigate the attenuation principle of wind energy quality. Inspired by the superior hydrodynamic performance of Dall's porpoise, a novel asymmetric airfoil design method is proposed. Unlike previous bio-inspired airfoil designs, the geometric morphometric-based outline method and the average morphological of multiple Dall's porpoise samples is applied. The results indicate that: (1) Wind energy quality in the upwind region is higher than that in the downwind region. At the tip speed ratio (TSR) of 1.2, the downwind wind speed is 55.8 % of the upwind speed. (2) The asymmetric bio-inspired airfoil demonstrates a higher power coefficient compared to the NACA 0018 airfoil. (3) At TSR = 0.5, the bio-inspired airfoil achieves a 42.3 % improvement in wind energy utilization. The proposed design methodology for asymmetric bio-inspired airfoil offers valuable insights into blade and airfoil optimization.