Non-linear dynamic analysis of a wind turbine blade

Wind turbine blades' dynamic behavior must be well investigated during the design process in order to avoid resonance. Modal analysis and nonlinear dynamic analysis of a rotating wind turbine blade are presented in this paper to study the effects of rotation speed on the natural frequencies and displacements. Accordingly, an enhanced finite element formulation based on uncoupled translational and rotational displacements' kinetic energy was developed. A twisted wind turbine blade was discretized using beam elements with different cross sections; each has six degrees of freedom per node. At rest, the model results were validated using ABAQUS software. Furthermore, the effects of geometrically non-linear phenomena produced by blade displacement on the vibration characteristics of the rotating blade have been discussed. The blade non-linear problem was solved by applying the Newmark method combined with the Newton-Raphson schema. Results show that the blade natural frequencies and displacements increase under angular rotation speed augmentation. This work highlights the significant sensitivity of the blade vibration characteristics to the geometric non-linearity. Accordingly, a modal and a linear analysis are insufficient to precisely estimate the dynamic behavior of a rotating turbine blade.