Overview

Rotordynamics is that branch of systems dynamics dealing with mechanical devices in which at least one part, usually defined as rotor, rotates with significant angular momentum. Following the ISO definition, a rotor is a body suspended through a set of cylindrical hinges or bearings that allows it to rotate freely about an axis fixed in space. This definition is, however, too restrictive, because there are cases in which no material bearings constrain the position of the rotation axis in space: A spinning projectile or space vehicle thus can be also regarded as rotors; aside from the artificial rotors built by human technology, it is also possible to find natural rotors like spinning celestial bodies. The dynamic behavior of stars that spin at very high speeds, as neutron stars, display features that are typical of rotors.

Rotors provided with material bearings to constrain their spin axis in a more or less rigid way to a fixed position in space are usually referred to as fixed rotors, whereas those that are not constrained in any way are defined as free rotors. In the first case, the spin speed is usually considered as constant or at least as imposed by a driving device, whereas the speed of the latter is governed by the conservation of the angular momentum.

The parts of the machine that do not rotate are generally referred to with the general definition of stator.

Rotordynamic studies related to technological applications date back to the second half of the nineteenth...