Experimental and Numerical Study of Rotor Dynamics of a Two- and Three-Bladed Wind Turbine

In this paper the dynamics of a two-bladed turbine is investigated numerically as well as experimentally with respect to how the turbine frequencies change with the rotor speed. It is shown how the turbine frequencies of a two-bladed rotor change with the azimuthal position at standstill and how the frequencies change due to rotor rotation. The frequency of the asymmetric rotor modes changes with multiple P contributions, not only with ±1P, as has previously been seen for threebladed wind turbine rotors. A three-bladed turbine is also analyzed in a similar way, and the results are compared. This turbine is investigated both in a perfect isotropic condition, where all blades have identical properties, and in an imbalanced edition, where one blade had increased mass.