Numerical Study on Stall Flutter of a Compressor Cascade : 1st Report, Numerical Method and Numerical Example

Stall flutter of a compressor cascade is studied by the numerical analysis of the unsteady separated flow around the blades oscillating in a torsional mode. A numerical method is developed for the present study, in which used are a discrete vortex modeling to calculate the convection and the diffusion of vorticity in the separated flow and a grid system deforming together with blade oscillation. The present method is applied to a compressor cascade working at an inlet flow angle where the rotating stall is also liable to occur. The numerical result shows that the strong vortices shed from the leading edge of stalled blades have dominant influences both on the flow behavior and on the flutter excitation of blades, and that the occurrence of stall flutter is closely connected with the propagation of rotating stall.