This paper reports the findings of a flutter investigation on a low-pressure turbine blade using a 3D, non-linear, integrated aeroelasticity method. The approach has two important features: (i) the calculations are performed in a time-accurate and integrated fashion, whereby the structural and fluid domains are linked via an exchange of boundary conditions at each time step, and (ii) the analysis is performed on the entire bladed-disk assembly, thus removing the need to assume a critical vibration mode shape. Although such calculations are both CPU and in-core memory intensive, they do not require prior knowledge of the flutter mode and hence allow a better understanding of the aeroelasticity phenomena involved.

The flow is modelled inviscidly but the steady-state viscous effects are accounted for using a distributed loss model. The structural model was obtained from a standard finite element (FE) representation and a large number of assembly modes were included in the calculations. The study focused on three part-speed conditions at which a number of unstable modes were known to exist from the available experimental data. The whole assembly was modelled using about 664,000 mesh points and predictions were made of aeroelastic modal time histories. From these time histories it was possible to identify the forward and backward travelling waves and to deduce the unstable modes of vibration. The theoretical predictions were found to be in very good agreement with the experimental findings.