The dynamics of rotors running on lubricated bearings is complex. While the linearized analysis allows to study the stability in the small and phenomena like oil whirl and oil whip, more complex behaviour, that may include chaotic motion, requires a fully nonlinear analysis. Since lubricated bearings behave like anisotropic supports, complex whirling pattern can be expected when the rotor is anisotropic. The aim of the present paper is to investigate to what extent the anisotropy of the rotor affects its dynamic behaviour. In particular, the interactions between the instability ranges due to rotating anisotropy and to oil whip are searched. The rotor models are built using DYNROT FEM code to build the basic rotor model and to obtain linearized solutions. The linear model of the rotor is then mated to nonlinerar bearing models and integrated numerically in time. Time domain results allow to draw some general conclusions applicable to simplified models as well as to real-world rotors.

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