Interaction of acoustic and vortical disturbances with an annular cascade in a swirling flow

A linearized Euler formulation is developed for the interaction and scattering of incident acoustic and vortical disturbances by an unloaded annular cascade in a swirling flow. Exact nonreflecting boundary conditions for the scattered sound are applied at the inlet/outlet of the computational domain. An explicit primitive variable scheme is implemented and validated by comparison with-the uniform flow and narrow annulus limits. Acoustic and aerodynamic results are presented and show that the swirl changes the amplitude and radial phase of the incident disturbances and modifies the number and radial shape of the acoustic modes in the duct. These changes have significant effects on the aerodynamic and acoustic response of the cascade.