On the Mechanism of Lateral Asymmetry of Noise Emission from a Propeller Installed Near a Wing

The effect of lateral asymmetry in the radiation pattern of a propeller installed near the wing is studied. Within the framework of a simplified theoretical model of the propeller loading noise and its shielding by a half-plane, as well as using numerical modeling of the interaction of the propeller with a flat finite plate, it is shown that when the propeller and the scattering surface are close to each other, a significant lateral asymmetry of the propeller tonal noise emission in the far field appears. The mechanism of this effect, which accompanies the symmetrical sound directivity of the propeller itself and the symmetry of the scatterer (wing), is associated with the phased summation of the sound field emitted directly by the propeller and the secondary sound field generated on the surface of the wing due to the scattering of disturbances (mainly hydrodynamic) created by the propeller on the leading edge of the wing. Thus, the study demonstrated that the presence of lateral asymmetry in the noise radiation pattern inherent in propeller-driven aircraft is a consequence of the interaction of the propellers and closely spaced wings.