Abstract
With the increasing size of wind turbines and the trend toward longer and more flexible blades, the aeroelastic response of blades has become significant. To achieve efficient and high-fidelity modeling, a new approach is required. In this study, a parametric two-dimensional cross-sectional model is developed based on the Variational Asymptotic Method, retaining Saint-Venant free warping. Vlasov theory is incorporated to add the warping-rigidity term associated with longitudinal variation in the torsion rate to the energy functional, thereby representing non-uniform-warping energy. To address the taper effect in variable-section blade structures, dimensionally consistent offset- and gradient-dependent correction terms are introduced through Tapered Beam Modification (TBM) to establish an expression for tapered torsional stiffness. Numerical results are presented for a tapered beam, a uniform composite beam, and the NH1500 blade; the method is then applied to the IEA 15-MW blade. The results show that, for the tapered beam, TBM reduces the deviation in the global frequency-equivalent stiffness from 4.2% to 2.1%, while for the IEA 15-MW application the peak sectional correction is 3.88% at x = 0.320 and the first torsional frequency differs by 5.21% between the two reduced-order models. The reported time-domain and AEP differences quantify sensitivity to the structural model.