A frequency domain approach for the prediction of tonal noise emitted by rotors in arbitrary steady motion

A novel frequency-domain formulation for the prediction of the tonal noise disturbance induced by rotating blade systems in arbitrary steady motion is presented. It is derived from the time-domain Farassat 1A boundary integral formulation for the solution of the Ffowcs-Williams ans Hawkings equation, and represents thickness and loading noises as harmonic responses to body kinematics and aerodynamic loads via frequency-response- function matrices. The proposed frequency-domain solver is applicable to those configura- tions for which the sound pressure levels of discrete tones are generally much higher than those of broadband noise. The numerical investigation concerns the analysis of the tonal noise produced by a helicopter rotor, as well as the examination of the pressure disturbance radiated by the interaction of a marine propeller with a non-uniform inflow. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.