A REDUCED-ORDER MODEL OF UNSTEADY FLOWS IN TURBOMACHINERY

A novel technique for computing unsteady flows about turbomachinery ca scades is presented. Starting with a frequency domain CFD description of unsteady aerodynamic flows, we form a large, sparse, generalized, n on-Hermitian eigenvalue problem that describes the natural modes and f requencies of fluid motion about the cascade. We compute the dominant left and right eigenmodes and corresponding eigenfrequencies using a L anczos algorithm. Then, using just a few of the resulting eigenmodes, we construct a reduced order model of the unsteady flow field. With th is model, one can rapidly and accurately predict the unsteady aerodyna mic loads acting on the cascade over a wide range of reduced frequenci es and arbitrary modes of vibration. Moreover, the eigenmode informati on provides insights into the physics of unsteady flows. Finally we no te that the form of the reduced order model is well suited for use in active control of aeroelastic and aeroacoustic phenomena.