Open rotor tone scattering

This paper describes a method for calculating the scattering of open rotor tones by an adjacent surface such as the aircraft fuselage or wing. This is of practical importance because shielding by these structures could be used to significantly reduce community noise levels. In the first part of this paper the propeller is modelled as a rotating point source and the effect of propeller translation is neglected. The scattering of sound from this rotating point source by either a rigid circular cylinder or a rigid half-plane is calculated and the reflection/shielding effect is clearly demonstrated. In the second part of this paper, the point source/stationary medium model is extended to include the effect of distributed sources and a moving medium. The extended model is then applied to calculate the effect of scattering of rotor-alone tones by a wing (which is modelled as an infinite half-plane). The effect of wing sweep and the application of the Kutta-condition at the trailing edge is investigated. An approximate method for quickly calculating open rotor tone scattering is also developed and validated.