Stationary or Dynamic Analysis

When using the Solid Rotor interface in the Rotordynamics Module, you must adopt a view where the concepts of what is static and what is dynamic deviate somewhat from the common conceptions.

In a general structural mechanics setting, different forms of dynamic analysis are used when inertial forces cannot be ignored. As the Solid Rotor interface is formulated in a corotating frame, some of the inertial effects are already taken into account as static loads. Thus, a rotor that spins under conditions that are stationary when viewed by a corotating observer does not require a dynamic analysis.

On the other hand, a load that is fixed in the spatial frame, like gravity, will have a harmonic variation when seen from the corotating perspective, and it provides a dynamic excitation.

As opposed to the Solid Rotor interface, the Beam Rotor and Solid Rotor, Fixed Frame interfaces are still formulated in a space-fixed frame, and hence the sense of static and dynamic loads does not change for these interfaces. However, effects of the rotor spin are already taken into account in the Beam Rotor interface through gyroscopic moments.