Sensitivity of the aerodynamics damping coefficient prediction to the turbulence modelling conjugated with the vibration mode shape.

The flutter corresponds to an aerodynamic loading of the structure which amplifies the natural blade vibration. In this paper, a modern design of a high pressure compressor is investigated using a time-linearized RANS solver on 2D blade to blade channel. Two operating points at part speed have been selected, the first with only small supersonic pockets and the second with the interblade channel blocked. Two vibration modes are investigated, the first torsion mode (with a nodal diameter at 2) and the first flexion mode (with a nodal diameter at 2, 4 and 6). Two different two equations turbulence models, k-l and k-ω have been used to resolve the steady state. The unsteady resolution is based on the previous steady state field. Turbulent variables are calculated over time based on a k-ω turbulence model. It was found that for some mode shapes, but not for all, the work exchange between the flow and the blade presents a large disparity depending on the turbulence model used primarily in the steady calculation. This paper proposes a parametric study in terms of rotor velocities, nodal diameters and vibration mode shapes to determine which flow phenomena are sensitive to the turbulence modelling. Main results point to the effect of the shockwave motion, and its interaction with the boundary layer and its separation.