Aeroelastic Stability Analysis of a Non-Rotating Annular Turbine Test Rig: a Comparison Between a Linearized and a Non-Linear Computational Method

During the ongoing research project on turbomachinery Computational Aeroelasticity (CA) and Computational AeroAcoustics (CAA) carried out at the Department of Industrial Engineering (University of Florence), an aeroelastic and aeroacoustic solver, named Lars, has been developed to perform flutter analyses and tone noise evaluations on axial turbomachine blade rows. This solver implements a time-linearized computational method and is designed to work together with the Traf steady/unsteady aerodynamic solver. More recently, the Traf aerodynamic solver itself has been extended to simulate unsteady flows around vibrating blades, thus implementing an aeroelastic non-linear method with phase-lagged periodicity boundary conditions. These two computational methods have been applied to assess the flutter stability of a non-rotating annular turbine test rig measured in a controlled vibration experimental campaign by the Ecole Polytechnique Fédérale de Lausanne (Switzerland), within the European research project FUTURE. The linearized and non-linear numerical results are compared with each other and with the experimental data, thus discussing the pros and cons of the two methods.