On the Effect of Frequency Separation, Mass Ratio, Solidity and Aerodynamic Resonances in Coupled Mode Flutter of a Linear Compressor Cascade

Abstract

At a low mass ratio of structure to air, the work-per-cycle approach, or better known as the energy method, will lead to non-conservative results as aerodynamic coupling of modeshapes acts destabilizing. Using the p-k method to solve the aeroelastic stability equation, the effects of various structural aspects are investigated for a two-dimensional compressor cascade in subsonic and transonic flow conditions. The investigated key parameters are frequency separation, mass ratio and solidity. Furthermore, the effect of a high frequency dependency of the aerodynamic forces is presented. Such phenomena can happen in case of aerodynamic or acoustic resonances. If the resonance peaks are close to the aeroelastic frequency, a discontinuous behavior of the frequency or damping solution can lead to a rapid destabilization of the system, once the aeroelastic frequency moves from one side to the other of the peak. In these regimes, it is crucial to have a high quality representation of the frequency-dependent generalized aerodynamic forces for an accurate prediction of the flutter onset.