22 Fluid-Induced Instability

Fluid-induced instability is a condition that is caused by rotor interaction with a surrounding fluid. It can produce large amplitude, usually subsynchronous, self-excited vibration of a rotor, leading to rotor-to-stator rubs on seals, bearings, impellers, or other rotor parts. The vibration can also produce significant alternating stresses in the rotor, leading to fatigue failure. Because it is so potentially damaging, fluid-induced instability should be eliminated and avoided.