Prediction of Sound Scattered by Moving Bodies with Application to Propeller-Driven Airplanes

This paper deals with the acoustic field generated by rigid bodies in arbitrary motion. The Ffowcs Williams and Hawkings equation is the starting point for the derivation of a boundary integral formulation for the acoustic disturbance. It yields a unified approach for the prediction of both sound generated aerodynamically and sound scattered by arbitrarily moving, (eventually) vibrating, surfaces impinged by an acoustic signal. The advantages of the acoustic formulation presented here with respect to other approaches that are commonly used are discussed. A boundary element method is applied for its numerical solution and the resulting prediction tool is validated by analysing the problem of low-frequency and high-frequency plane waves impinging on a rigid sphere. Then, the formulation is applied to an aeronautical configuration for the determination of the scattered pressure field generated by a fuselage impinged by the incident pressure wave emitted by a propeller.