Multiwave Vibrations in Mistuned Cascades With Tip-Shroud Friction

Measurements taken during aero engine tests and in the field showed that flutter vibrations of shrouded blades can feature rich wave content (multiwave flutter vibrations). In a previous work, we demonstrated that this behavior can be explained by the nonlinear interaction of aeroelastically unstable traveling wave modes. The resulting vibrations are quasi-periodic. In this work, we show that the nonlinear modal interaction is not strictly needed, but actually mistuning alone can explain the multiwave form of flutter vibrations. The resulting vibrations are periodic and dominated by only a single mode shape of the mistuned system. However, unrealistically high mistuning intensities are needed to obtain significant contributions of multiple wave forms under the considered strong inter-blade coupling. Thus, we conclude that mistuning cannot explain the rich wave content observed in the measurements. Moreover, mistuning tends to hamper the nonlinear modal interactions and, thus, the occurrence of quasi-periodic multiwave flutter vibrations. This implies that intentional mistuning is not only useful to stabilize flutter but might also play an important role in developing flutter-tolerant blade designs.