A novel ROM-based FSI model of composite blisk with blades-disk coupling for flutter analysis

With the trend of blisk becoming lightweight, compact, and material-composite, fluid-structure interaction (FSI) in blisk flutter analysis becomes increasingly unignorable. Direct numerical simulation of FSI consumes a large amount of computing resources, and there has been very little research on the mechanism of influence of blades-disk coupling on the flutter characteristics of blisk. This paper proposes a novel low-dimensional FSI model which is integrated with blades-disk coupling and composite materials, for the study of composite blisk flutter analysis. The structural dynamics subsystem is built using a semi-analytical global modal method, while the aerodynamic subsystem is built using a reduced-order method based on system identification. The FSI model proposed in this paper is firstly validated by existing blisk aeroelastic examples, and then extended to study blades-disk coupling, modes coupling, bending-torsion coupling, and material parameter studies. The results show that the dramatic increase in the degree of blades bending-torsion coupling caused by blades-disk coupling is the main reason for the sharp decrease of aeroelastic stability of flexible-disk blisk, especially in the low nodal diameter (ND) mode of each modes set, the modes coupling occurs in the double combination modes of blisk which are time-depend orthogonal in FSI modes, and the dual regulation of material parameters on density and elastic constants makes the effects of material parameters on the two blisk mode sets different. The FSI model and analysis results presented in this paper provide meaningful theoretical guidance for the aeroelastic design of composite blisk.