Nonlinear aeroelastic performance in 5 MW and 15 MW wind turbine blades using intrinsic geometrically exact method

Nonlinear aeroelastic challenges from large deformation and complex airflow in large-scale blades increasingly hinder the advancement of 15 MW + wind turbines. Conventional displacement-based geometrically exact beam theory suffers from accuracy and convergence issues in analyzing 100-m-class blades. To address this, the intrinsic geometrically exact blade model was developed for nonlinear aeroelastic analysis. This model accurately captures large deformations, multi-directional deformation coupling, and aero-structural interactions while integrating stably. Simulations of NREL 5 MW and IEA 15 MW blades under various conditions were conducted to assess the impact of long-flexible designs on aeroelastic behavior. Results show that under one-way loading, the linear model overestimated blade deflection, with maximum deviation increasing from 8.8 % (5 MW) to 13.9 % (15 MW), and the 15 MW blade showing a higher mean deflection deviation (11.7 %) in the tip region. For periodic steady aeroelastic responses at rated wind speeds, nonlinear effects more strongly affect the 15 MW blade. Minimum mean deviations of normal and tangential coefficients reduced to 13.5 % and 31.9 %, while the 15 MW blades exhibited 5.7 %, 17.7 %, and 22.8 % increases in maximum flapwise deflection, flapwise torsion, and edgewise torsion deviations over the 5 MW blade. Stiffness scaling further shows an expanded nonlinear region in the 15 MW blade, revealing the great effect of large-scale, flexible design on aeroelastic responses.