The paper is about the analytical modeling of sound generation and transmission in blade and vane rows of radial-flow turbomachines. Feasibility tests are made for a model centrifugal compressor with a vaned diffuser but the analysis holds for radial turbines as well, with the restriction that the flow must be subsonic in the parts of the architecture where the formulation is applied. The mathematical background is a two-dimensional theory of spiral modes superimposed on a spiral base flow, coupled with a mode-matching procedure. Typically, for a compressor, the inlet circle of the diffuser is considered as an interface where incident disturbances are scattered as reflected converging waves and transmitted duct modes into the inter-vane channels. The latter are assimilated to an array of purely radial, bifurcated waveguides. The matching procedure takes the tangential-velocity mismatch of the mean-flow into account. The incident disturbances are either prescribed acoustic waves, for the study of sound transmission, or hydrodynamic modes for the study of sound generation by wake impingement. Only the second case is addressed in detail. The effects of the mean flow and of the geometry on the scattered waves is discussed.
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