Vane sweep effects on rotor/stator interaction noise

The application of a lifting surface theory to compute the aerodynamic and acoustic response of swept vane stators to viscous rotor wakes is studied. Starting from the flow equations for a perturbed, axially subsonic flow, expressions are derived for the velocity field induced by a stator. A new representation of Green's function is used, which avoids the traditional expansion in duct modes. This representation is more practical for arbitrary vane shapes than the classical one. The boundary condition at the vane surfaces yields an integral equation for the unknown pressure jump distribution over the vanes. A Galerkin projection transforms this integral equation into a set of linear equations that is solved numerically. The new method agrees with the classical method and with experimental data for zero sweep. Sample calculations show that vane sweep can be exceptionally effective in the reduction of noise resulting from the interaction of rotor wakes and a stator.

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