Aeroelastic characteristics and mechanism of plunging mode in turbine cascades under transonic buffet flow

The transonic flow is prevalent in the aerospace field. It is characterized by a complex flow mechanism and can induce intricate aeroelastic phenomena, resulting in substantial structural vibrations or even fractures. The computational fluid dynamics/computational structural dynamics (CFD/CSD) method and reduced-order model (ROM) method are both used to analyze aeroelastic characteristics of the cascade plunging mode under transonic buffeting flow. Different from the pitching mode, the plunging-mode structural responses obtained by the CFD/CSD method remain stable in both subcritical and supercritical buffeting flows. To analyze the phenomenon, an aeroelastic model based on the ROM method was established. An unsteady aerodynamic force model was established under subcritical flow conditions based on the dynamic linear flow assumption. Coupling the unsteady aerodynamic force model with the structural motion equations, an aeroelastic model was developed, translating the aeroelastic analysis of the cascade into the problem of analyzing the characteristics of the aeroelastic model. The eigenvalue trajectories of the aeroelastic model are obtained by varying the structural stiffness. The results demonstrate that the stability of the 1 nodal diameter (1ND) mode near the buffet flow frequency region is strengthened due to the mutual attractive behavior with the buffet fluid mode (FM). In contrast, the instability of the 1ND mode in the low-frequency region arises from the mutual exclusion with the zero-frequency FM.