Investigation on dynamics of rotating wind turbine blade using transferred differential transformation method

The wind turbine blade is commonly treated as a non-uniform beam because of its high aspect ratio. The bend-twist coupled vibrations of the wind turbine blade occur when there exist the misalignments among the shear center, neutral axis and pressure center in the blade cross-section. The differential governing equations of motion for the rotating wind turbine blade are derived by Hamilton principle and solved by the transferred differential transformation method (TDTM). Due to the rotations, three terms, namely the tension, centrifugal and gyroscopic forces, are distinctively summarized and taken into account in the proposed model. The natural frequencies obtained by the TDTM are compared with both experimental and numerical simulations to validate the effectiveness of the proposed solving method. The influences of the tension, centrifugal and gyroscopic forces on the natural frequencies are investigated for the wind turbine blade. The mode veering phenomenon is found and explained by using the complex mode decomposition theory. The phase differences among the flap-wise, edge-wise and torsional motions are also explored by observing the whirling orbits at the blade tip.