Whirl flutter analysis of a wind tunnel model using multidisciplinary simulation and multibody dynamics

Kurzfassung

Whirl flutter is a dynamic instability known mostly from tilt-rotors and prop-airplanes. For a tilt-rotor or prop- airplane, from one side the gyroscopic effect of the rotating rotor/propeller causes the coupling of the elastic modes of the propeller-nacelle system and produces the so-called whirl modes and from the other side the unsteady aerodynamic forces/moments generated due to the whirl modes change the damping of the system. With the reduction of the damping, the whole system can reach a zero or negative damping resulting in an oscillation of the system with constant or increasing amplitude, respectively. Classical analysis of whirl flutter is limited to a system with reduced degrees of freedom. However, going beyond this classical approach allows considering more physical effects. In this work a multidisciplinary simulation of the whirl flutter phenomenon is introduced. Different simulation codes are used to create the model and to simulate the physical effects. A FEM code is used to model the elasticity of the wing and nacelle. A propeller comprehensive code is utilized to consider the propeller induced velocity field for the calculation of the propeller aerodynamics. The full model is then implemented within a multibody simulation tool, which allows performing the dynamic stability analysis. The method introduced in this paper can be used for the whirl flutter investigation of any configuration.