A PROCEDURE FOR THE EVALUATION OF INSTALLED PROPELLER NOISE

A method for the prediction of the acoustics of a propeller in the flow-field of a wing is presented. The method is used to study the noise generated by the unsteady loading induced on the propeller as it passes through the wing flow-field. Both the aerodynamic and acoustic methods are previously proven techniques, the aerodynamic method being based on a combination of free wake analysis and a three-dimensional boundary element method, while the acoustic calculation is a full-surface, moving medium form of the Ffowcs Williams–Hawkings equation. Calculations are presented for a reference case of a four-bladed low-speed propeller in forward flight. The acoustic predictions are supplemented with retarded time results which relate the radiated noise to the aerodynamic conditions on the blade at the time of noise emission. The noise data and the retarded time results are discussed and related to previous aerodynamic work.