Implementation of the “Harmonic Variables” concept in the vibration analysis of a coupled rotor/fuselage system

The paper presents a new numerical technique for deriving and solving the nonlinear periodic equations of motion of a coupled rotor/fuselage system. The method is based on the combination of the concept of working with “Harmonic Variables” with general purpose nonlinear solvers. The resulting technique substantially reduces the required analytical effort while preserving high accuracy solution and symbolic harmonic resolution. For demonstration purposes, the present nonlinear modelling consists of elastic blades and fuselage, and contains nonlinear elastic and dynamic contributions. The method is demonstrated by a study of the influence of possible fuselage responsiveness on the vibratory hub motion and hub loads