Computation of the noise of a subsonic propeller at an angle of attack

Computation of propeller noise due to inflow distorsions is essential to evaluation and reduction of aircraft noise. The angle of attack, the simplest such distorsion seen by the propeller blades, is known to have a double effect on sound generation — mostly an aerodynamic effect, but also a kinematic effect which amplifies the source strengths — and propagation. The research presented in this paper is aimed at investigating numerically those effects thanks to the use of a computer program developed for that purpose. After a brief reminding of the background theory, the numerical methods are described and finally computational results are obtained using unsteady aerodynamic measurements performed during wind-tunnel tests. The importance of both the so-called aerodynamic effect and kinematic/acoustic effect is thus confirmed.

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