On the effect of support asymmetry on rotordynamic instability

One of the causes of rotor instability is the damping of the rotating parts of the system. Its de-stabilizing effect can be counteracted only by introducing a suitable non rotating damping. It is well known that the instability threshold increases at increasing ratio between non rotating and rotating damping. The aim of the present paper is showing that support anisotropy tends to increase the stability of the system, by increasing the instability threshold. This effect is however present only if this anisotropy causes the whirl orbits to become elliptical