The linear stability characteristics of flap-lag-torsion horizontal axis wind turbine blade are investigated. The partial differential equations of elastic rotating cantilever blade subjected to combined flap/lead-lag/torsion motion are obtained. The aerodynamic forces are introduced from extensive Theodorsen's theory based on a quasi-steady approximation. Galerkin's method together with eigenvalue analysis and time integration are used for stability analysis. The locus of roots of flap-lead,lag and torsion fundamental mode with increasing wind speed are obtained. The effects of inplane configurations, torsion natural frequency and precone angle on the aeroelastic stability o f the blade are shown. The effect of the number of mode shapes on accuracy and convergence is also examined. Finally, the results based on eigenvalue analysis is compared with the time simulations of deflections of the blade.
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