A FLUTTER MODEL FOR ROTOR BLADESWITH FLAPS

摘要

A three-dimensional, frequency-domainrnflutter theory for a five Degree-of-Freedomrn(5DOF) system for rotor blades with trailingedgernflaps is developed. Lagrange’s equationrnusing superposition of normal modes and thernaerodynamic forces and moments given by twodimensionalrnstrip theory for an incompressiblernflow is applied to develop a flutter solution. Inrnorder to solve the flutter problem, the freernvibrations for both the bending and torsionalrnmode shapes and natural frequencies for thernrotating blade are determined. To model thernflap, the stiffness of the torsional spring for thernflap is tuned such that the flap rigid bodyrnuncoupled natural frequency can be equated tornthe flap input frequency, thus allowing analysisrnof the effect of flap input frequency on the flutterrnsolution.rnThree-dimensional aspects are includedrnwith sectional variations of mass, geometry andrnfreestream velocity. Aerodynamic effects arernexamined through different lift deficiencyrnfunctions. It is assumed that the aerodynamicrnforces and moments do not change thernuncoupled modes shapes. Practical applicationrnis demonstrated using a hingeless rotor blade.