Reduced order modeling of a bladed rotor with geometric mistuning: Alternative bases and extremely large mistuning

This paper represents further development of Modified Modal Domain Analysis (MMDA) (Sinha, 2009), which is a breakthrough method for the reduced-order modeling of a bladed rotor with geometric mistuning. The bases vectors for model reduction in MMDA have been formed using the mode shapes of cyclic sectors with blades' geometries perturbed along the POD (Proper Orthogonal Decomposition) features. The use of mode shapes from modal analyses of cyclic sectors perturbed along the POD features adds an additional step of creating the finite element models of artificially perturbed geometries. Here, an alternative formulation of MMDA is presented in which bases vectors are created from cyclic sectors with actual blades. Therefore, the additional step of creating artificial blades with geometries perturbed along POD features is avoided. The MMDA is also extended to a bladed rotor in which a few blades have extremely large mistuning; for example, blended airfoils. The validity of proposed approaches is shown by comparing with ANSYS results for full (360 degree) bladed rotor.