Bio-Inspired Outer-Span Hybridization of the NREL Phase VI Rotor for Enhancing Aerodynamic Performance and Flow-Field Stability

Abstract. The presenting work evaluates a selective bio-inspired outer-span hybridization of the NREL Phase VI wind turbine rotor. An owl-inspired airfoil (OA-T), obtained through controlled thickness scaling of a reconstructed owl-wing section, is integrated over the outer 20 % of the blade span while preserving the original chord and twist distributions. The objective is to assess whether localized geometric modification in the torque-dominant tip region can improve aerodynamic performance under increasing loading. A validated CFD framework is employed at both airfoil and rotor scales. Transition SST simulations reproduce the experimental lift behavior of the owl-inspired airfoil, while steady RANS–MRF simulations capture the torque response of the baseline Phase VI rotor. Using the same modeling setup, the hybrid configuration demonstrates a systematic increase in peak power coefficient from 0.38 to 0.42 at a tip speed ratior λ = 5.41, reaching 0.448 at higher tip-speed ratios. Flow-field analysis reveals outward redistribution of tangential loading, a shift toward a more chordwise-distributed pressure response, delayed separation progression, and a more confined wake structure at elevated wind speeds. The results show that controlled outer-span hybridization within a benchmark rotor can enhance torque retention and aerodynamic stability without full-blade redesign.