Aeroelastic response of a coupled rotor/fuselage system in hovering and forward flight

The aeroelastic response analysis of a coupled rotor/fuselage system is app roached by iterative solution of the blade aeroelastic response in the non- inertial reference frame fixed on the hub, and the periodic response of the fuselage in the inertial reference frame. A model of the coupled system hi nged with the flap and lag hinges, the pitching bearing which may not coinc ide with the hinges, and the sweeping-blade configuration is established. T he moderate-deflection beam theory and the two-dimensional quasi-steady aer odynamic model are employed to model the aeroelastic blade, all the kinetic and inertial factors are taken into account in a unified manner. A five-no des, 15-DOFs pre-twisted nonuniform beam element is developed for the discr etization of the blade, three rigid-body-motion DOFs are introduced for the motion of the hinges and the bearing. The Hamilton's principle is employed to evaluate the equation of motion of the blade. The derived nonlinear ord inary differential equations with time-dependent periodic coefficients are solved by a modified quasi-linearization method, which is developed for the higher DOF periodic system. The resulting periodic forces and moments exer ted on the fuselage by all the blades are evaluated every time, when the co nverged nonlinear periodic response of the blade is obtained under the cons ideration of the equilibrium of the blades. The fuselage structure is simpl ified to be a beam structure, the governing equation is established in the inertial reference frame and a two-nodes beam element is used to discretize the flexible fuselage. The periodic response of the fuselage is solved by a simple shooting method. The iteration of the rotor/fuselage response is c ontinued, until the aeroelastic responses of the blade and the fuselage con verge simultaneously. Both the hovering and the forward flight states can b e considered. The results of a computed numerical example by the developed program are presented to verify in practice the economy of the modeling as well as the reliability and efficiency of the corresponding solving methods .