Rotating machines such as steam or gas turbines, turbo-generators, internal combustion engines, motors, and disk drives can develop inertia effects that can be analyzed to improve the design and decrease the possibility of failure. Current trends in rotating equipment design focus on increased speeds, which increase operational problems caused by vibration. At higher rotational speeds, the inertia effects of rotating parts must be consistently represented to accurately predict rotor behavior.

Inertia effects in rotating structures are usually caused by gyroscopic moment introduced by the precise motions of the vibrating rotor as it spins. As spin velocity increases, the gyroscopic moment acting on the rotor becomes critical. Not accounting for inertia effects at the design level can lead to bearing and support structure damage. It is also important to consider bearing stiffness, support structure flexibility, and damping characteristics to understand the stability of a vibrating rotor.

In the sections that follow, modeling details and analysis procedures for a rotating structure are detailed. Generally, a 3D model directly available from the CAD can be used for the analysis; however, 3D models result in a large number of nodes and elements models. This example demonstrates how to extract a plane 2D model from the 3D model, which can be analyzed using far fewer nodes and elements. The ease of use, accuracy, and performance of 2D and 3D model analyses are compared.

For more information about rotordynamics, see the Rotordynamic Analysis Guide and Rotating Structure Analysis in the Advanced Analysis Guide.