Approximate method for the prediction of propeller noise near-field effects

Abstract

An approximate frequency-domain method is described for predicting the near-field noise levels generated by a high-speed propeller; a near-field to far-field transfer function is defined, and estimated by way of a point force approximation and asymptotic techniques. The transfer function can then be quickly and easily applied to correct existing far-field prediction schemes for near-field effects, representing a considerable simplification over existing frequency-domain methods, as well as providing explicit scaling laws and design information. The method is valid across the whole range of propeller operating conditions (for both single-rotation and centrarotation systems), and its accuracy is demonstrated at each stage by comparison with experimental data.