Three-Dimensional Viscous Flutter Analysis of Standard Configuration 10

The results of a three-dimensional (3D) viscous flutter analysis for a compressor stage, Standard Configuration 10, are presented. The unsteady flow simulations were performed by a 3D linearized Navier-Stokes flow solver using the Spalart and Allmaras turbulence model. Significant flow blockage due to corner separation at the hub on the suction surface was predicted by the steady-state 3D viscous simulation at a design condition. Corner separation was not predicted by 3D inviscid or two-dimensional (2D) viscous simulations. The corner separation was found to have a destabilizing effect and changed the nature of the unsteady flow. In fact, the 3D viscous simulations predicted negative aerodynamic damping for almost half of the inter-blade phase angles, while the 2D and 3D inviscid simulations predicted stable positive aerodynamic damping for all inter-blade phase angles. An off-design flow condition was also examined and significant differences between the 2D and 3D viscous simulations were found.