Frequency Lock-In Phenomenon of Vortex Induced Vibration of a Rotating Blade Considering Bending-Torsion Coupling Effect

A rotating thin blade with bend-torsional coupling subjected to vortex induced vibration (VIV) is considered in this paper. It is necessary to study the motion coupled bending torsion due to the discordant centroid and shear center and the effect of centrifugal force at high-speed. The blade with a single axisymmetric section is regarded as a beam instead of an oscillator. The motion equation coupled bending-torsion of the blade is established by using the Euler-Lagrange equations, and the effect of centrifugal force is also employed. Vortex shedding is described by a nonlinear oscillator satisfying Van Der Pol (VDP) equation. Ritz-Galerkin method is employed to simplify the equations of the blade, and the interaction between the bending and torsion modes of blade and wake modes is discussed. The motion equation is simplified based on the contribution of the blade flutter mode. Furthermore, the single-mode approximation is used to investigate the effects of mass ratio, damping, and coupling coefficient on the locking phenomenon. It is also analyzed that the variation of flutter amplitude and locking region of the rotating blade considering bending-torsion coupling.