Computational prediction of stall flutter in cascaded airfoils

Abstract

At off-design conditions turbomachines may experience flow separation from the cascaded airfoils and the circumferential pattern of stalled and unstalled airfoils propagates about the flow annulus. The unsteady periodic nature of propagating stall will force blade vibration; stall flutter of the blades may occur if stall synchronization occurs and the propagation frequency is entrained by the blade natural frequency. A computational scheme based on a modified form of the vortex method is used to simulate the flow over an infinite linear cascade of airfoils.