Campbell diagram

A Campbell diagram plot represents a system's response spectrum as a function of its oscillation regime.

It is named for Wilfred Campbell, who introduced the concept.

[1][2] It is also called an interference diagram.

[3] In rotordynamical systems, the eigenfrequencies often depend on the rotation rates due to the induced gyroscopic effects or variable hydrodynamic conditions in fluid bearings.

It might represent the following cases: In acoustical engineering, the Campbell diagram would represent the pressure spectrum waterfall plot vs the machine's shaft rotation speed (sometimes also called 3D noise map).

Analytical Campbell Diagram for a Simple Rotor
Campbell Diagram of a steam turbine . Analysis shows that there are well-damped critical speed at lower speed range. Another critical speed at mode 4 is observed at 7810 rpm (130 Hz) in dangerous vicinity of nominal shaft speed, but it has 30% damping - enough to safely ignore it.