The Effect of Unsteady Aerodynamic Asymmetric Perturbations on Flutter

Nearly all turbomachinery aeroelastic analyses assume that the blades are “tuned” aerodynamically. That is, all blades experience identical steady and unsteady loads (except for an interblade phase shift). This paper presents the results of a perturbations sensitivity study of the effects of aerodynamic asymmetries on flutter of bladed disks. A high fidelity model including both structural and aerodynamic coupling is used. The types of asymmetry considered are single blade, symmetric group, and random. For the case of one blade perturbation, and symmetry group of 2 perturbations, the effect is to suppress flutter. This is similar to the effect of frequency mistuning. However, the results from random perturbations of all blades suggest that manufacturing variations or field damage may cause an engine to flutter. This provides a strong motivation to conduct additional research in this area.