Turbine engine rotors and bladed disks, which play a crucial role in the energy supply and mobility industries, are dynamic systems that are known to suffer from severe vibration problems. These vibrations may be introduced by aerodynamic forces. Hence, it is important to study the aeroelastic behavior of the blades in turbomachinery design.

Aeroelastic phenomena can be classified into two categories: forced-response and flutter. Typically, flutter is an asynchronous self-excited vibration, generally occurring at a frequency corresponding to one of the lower blade or coupled blade-disk natural frequencies. On the other hand, forced-response resonance of rotor blades generally results from periodic aerodynamic forcing functions with frequencies of integer multiples of the natural frequency of the system.

In general, a bladed disk is designed to have identical blades, but there are always random deviations among individual blades due to manufacturing tolerances, wear, and other causes. This is known as mistuning.

Though mistuning is typically small, mistuned bladed disks can have drastically larger forced-response levels than the ideal tuned design, which can cause blades to fail prematurely due to high cycle fatigue (HCF). HCF is a major cost, safety, and reliability issue for gas-turbine engines. It is clearly of great interest to be able to predict, and ultimately to limit, the increases in maximum blade response caused by mistuning.

Comprehensive modeling, analysis, and understanding of bladed disk vibration is therefore critical to reduce the occurrence of HCF and to improve the performance and reliability of turbomachinery.

For more information, see the Cyclic Symmetry Analysis Guide.