Direct simulation of acoustic scattering by a rotorcraft fuselage

A new technique is used to simulate the scattering of sound by a rotorcraft fuselage. In this technique, the scattering body is replaced by a region of different acoustic impedance. The main rotor is taken to be the noise source and is modeled by a rotating dipole. The linearized Euler equations are solved to get the near-field noise. The far-field noise is obtained by a numerical integration of the Ffowcs Williams-Hawkings equation in the near-filed. Comparisons are made between the noise levels obtained by the solution of these equations in the presence and in the absence of the fuselage. It is observed that both the near-field and far-field noise levels are significantly altered due to the presence of the scattering fuselage.