Eigenmode Analysis of Unsteady Viscous Flows in Turbomachinery Cascades

Stall flutter and rotating stall in turbomachinery cascades are recurring problems in the development and operation of gas turbine engines [see e.g. Sisto (1987)]. In this paper, we present a novel technique for analyzing unsteady flows called “reduced order modelling.” The method, which is based on the eigenmodes (natural modes) of unsteady fluid motion through a cascade, is useful for predicting unsteady flows in turbomachinery over a range of reduced frequencies. Furthermore, the resulting model is low-order, and provides physical insight into certain aeroelastic and/or fluid dynamic instabilities, e.g. rotating stall.