Multi-Scale Mapping of Sectional Stiffness Coupling in IEA 10MW,15 MW, and 22 MW Wind-Turbine Blades

Abstract. This study compares the spanwise stiffness and stiffness coupling characteristics of 10 MW, 15 MW, and 22 MW wind turbine blades using sectional 6×6 stiffness matrices extracted from NREL BeamDyn_blade input files. We define a normalized coupling coefficient and a root-mean-square (RMS) coupling score to map how axial–bending, shear–torsion, and bending–torsion interactions evolve along the blade span. With increasing scale, the 10 MW blade shows strong, localized coupling “hotspots” inboard, the 15 MW blade redistributes these interactions across mid-span, and the 22 MW blade exhibits weaker peak coupling but broader spatial influence extending toward the tip. This “smoothing with scale” indicates a design shift away from highly localized passive load alleviation and toward globally distributed aeroelastic tailoring for ultra-long (>130 m) blades. The method is fully reproducible from public OpenFAST model inputs. These findings provide crucial insights for the structurally-optimized and aeroelastically-stable design of next-generation megawatt-scale turbines.