Abstract

An important precursor to the dynamic analysis of rotating machinery, in either frequency or time domain, is the extraction of its mode shapes and corresponding frequencies. This is often presented as a Campbell diagram, which plots the frequency of each mode as a function of the rotor speed. A typical Campbell diagram has several backward whirl, linear and forward whirl modes leading to numerous intersections. Therefore augmenting the eigenvalue solution with a mode tracking algorithm to output the Campbell diagram is of essential interest to a practicing engineer. This paper presents an evaluation of several mode tracking approaches for rotor dynamic simulations, starting from their theoretical foundations to practical applications using several test cases. These tracking algorithms are implemented in the structural solver, OptiStruct, part of Altair Engineering’s CAE framework. Finally, the conclusions drawn from this exercise offer engineers studying rotating machinery several key insights.

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