Numerical modal analysis of DTU 10-MW reference wind turbine’s blade using modified Myklestad´s method

Abstract

Since the rotor blade system of an horizontal axis wind turbine is responsible for converting wind energy into mechanical, which turns into electrical and predicting its dynamic behavior is of vital importance. In that sense, this paper deals with performing a modal analysis of a blade belonging to the DTU 10-MW reference wind turbine by using a modified Myklestad’s method. The blade model was built on two different keystones, as follows: first, considering uncoupled bending in out-of-plane (flapwise) and in-plane (edgewise) directions and considering a coupled bending-torsion motion also in both directions. In order to accomplish these objectives, a Python code was implemented. The computed eigenfrequencies were compared to the results obtained for the blade by using the finite element method. Besides, the mode shapes were plotted and the centrifugal stiffening was also taken into account. Results suggest the feasibility of the modified Myklestad’s method for modal analysis purposes, since good agreement with reference data was achieved and considering that the Myklestad’s method has a considerably less complex implementation than the finite element method.