Green's function solution for forced vibration of wind turbine blades
By employing Euler-Bernoulli beam model and Greenberg expression,this paper builds the bending-bending-torsional coupled forced vibration equation of wind turbine blade.Based on the vibration equations,the displacement is decomposed into quasi-static displacement and dynamic displacement,and Fredholm integral equations for the forced vibration of wind turbine blades are obtained by Laplace transform and superposition principle.The semi-analytical solution of Green function for the coupled forced vibration of wind turbine blades is obtained by discrete equations.Through numerical calculation,the obtained solutions are compared with those in the existing literature to verify the accuracy of the understanding.Our results show:(1 )the dimensionless damping coefficient only exerts a great impact on the peak value of the first order natural frequency of the blade,and the vibration isolation region of the blade under flap vibration appears after the second order natural frequency,while the vibration isolation region under lead/lag vibration appears between the first and second order natural frequency;(2 )the effects of inflow angle and rotational speed of the blade on the vibration response of the blade are not negligible and the coupling vibration of the blade leads to a marked increase in the quasi-static displacement of the blade.
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