Investigating the nonlinear coupled vibrations of elastic blade of helicopter and analysis of flutter frequencies

Document Type : Research Article

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university of tabriz

Abstract

Aeroelastic instability in blades is one of the most important sources of instability in helicopter rotors, and the most critical of these instabilities is flutter. In this paper, in order to investigate the blade flutter and its relationship with the rotor structural parameters, using the Hamilton's principle and considering the Euler-Bernoulli beam theory, the coupled nonlinear partial differential equations governing the rotating elastic blade of a helicopter in the hover flight mode are extracted and converted into a set of ODEs by applying Galerkin method. Then the obtained equations for small perturbations are linearized around the steady state conditions. The effects of the gyroscopic couplings are investigated and assuming the harmonic response, the natural frequencies of the blade in three motion axes are calculated and the relationship between the natural frequency and flutter frequency of the blade with structural and aerodynamic parameters are shown. Using numerical simulation, the results for two types of soft and stiff blades with given characteristics in terms of different parameters such as blade twist angle, pre-cone angle and rotation speed of rotor for the first mode shape are extracted. Finally, the effect of each of the mentioned parameters on the flutter frequency and also, the blade stability region is analyzed. It is shown that by increasing the blade stiffness, the flutter frequency will increase and the system will be stable.

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Amirkabir Journal of Mechanical Engineering
Volume 55, Issue 12
March 2024
Pages 5-5

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