Aeroelastic response of a coupled rotor/fuselage system in hovering and forward flight |
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Authors: | Z-C Zheng G Ren Y-M Cheng |
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Institution: | (1) Department of Engineering Mechanics, Tsinghua University Beijing, 100084, China, CN |
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Abstract: | Summary The aeroelastic response analysis of a coupled rotor/fuselage system is approached 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 hinged with the flap and lag hinges, the pitching bearing which may not coincide with
the hinges, and the sweeping-blade configuration is established. The moderate-deflection beam theory and the two-dimensional
quasi-steady aerodynamic model are employed to model the aeroelastic blade, all the kinetic and inertial factors are taken
into account in a unified manner. A five-nodes, 15-DOFs pre-twisted nonuniform beam element is developed for the discretization
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 ordinary 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 exerted on the fuselage by all the blades are evaluated every time, when
the converged nonlinear periodic response of the blade is obtained under the consideration of the equilibrium of the blades.
The fuselage structure is simplified 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 continued, until the aeroelastic responses of
the blade and the fuselage converge simultaneously. Both the hovering and the forward flight states can be 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.
Received 4 May 1998; accepted 11 August 1998 |
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Keywords: | helicopter dynamics rotor/fuselage coupling aeroelastic response time-dependent periodic system nonlinearity |
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