PhD thesis: Time domain calculation of noise generated by a propeller in a flow

In this thesis, the problem of calculating the noise from an acoustically subsonic aircraft propeller is approached using a ``moving medium'' method. An established theory of noise generation by rigid bodies in motion is combined with the moving medium Green's function to develop a linear acoustic formulation for the sound radiated by a body in arbitrary motion in a uniform steady flow of arbitrary orientation. Results from a numerical code based on this formulation are then presented and compared to experimental results from a test campaign conducted as part of the EU-sponsored SNAAP (Study of Noise and Aerodynamics of Advanced Propellers) project. Near field acoustic results from two propellers, a conventional ``low speed'' propeller and an advanced ``high speed'' design, are presented for a range of operating speeds in the high subsonic to supersonic range. Further results are presented for the far-field noise of the low speed propeller operating at a low flight Mach number. In each case the blade loading distribution used in the calculations is interpolated from experimental data.

It is found that the numerical code predicts the experimental data quite well but is more accurate in predicting the noise from the high speed propeller than the low speed design, even for supersonic blade tip speeds (up to Mach numbers of 1.08). This and other features of the numerical predictions are discussed and explained.

It is concluded that the moving medium time domain method presented is useful and can be coded for efficient prediction of propeller noise.