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In this tutorial model, learn how to model multiple rotors connected through helical gears using the Rotordynamics Module, an add-on product to the Structural Mechanics Module and COMSOL Multiphysics®. When modeling geared rotors, the presence of gears in the system induces the lateral and torsional vibrations in the rotors. The gear mesh is assumed to be elastic, having a constant stiffness value.

We demonstrate an eigenfrequency analysis to compute the eigenfrequencies of the system for different speeds of the driving rotor. A transient analysis is also performed for the given speed of the driving rotor and the load torque on the driven rotor. With these analyses, we can compute the orbits of gear centers and forces on the bearings. The transient analysis is performed for both rigid and elastic gear mesh in order to analyze the effect of gear mesh stiffness on the rotor vibrations.

The simulation results for this tutorial model include a Campbell diagram showing the variation of eigenfrequencies with the rotational speed, critical speeds of the rotor, frequency response curves for the gear displacement and rotation, the von Mises stress distribution in the shafts, orbits of the gear centers in the rotating and fixed frames of reference, and the dynamic transmission error when transferring rotation from one shaft to another.