A propeller operating in a non-uniform flow can generate excessive noise. The non-uniform condition is inevitable for the aircraft with a pusher configuration, contra-rotating open rotors, or most of the marine propeller which operates in the wake of the ship. Therefore there is a need for studies by which the noise from the propeller in a non-uniform flow can be predicted theoretically and experimentally tested.

In this thesis, a propeller noise formulation in the frequency domain is derived from the Formulation 1 of Farassat. It includes loading and thickness noise. The feasibility of measuring marine propeller noise by wind tunnel instead of a water tunnel is studied. A Mach number scaling law of noise generated by a propeller in uniform flow is presented. Using this law, a...[ Read more ]

A propeller operating in a non-uniform flow can generate excessive noise. The non-uniform condition is inevitable for the aircraft with a pusher configuration, contra-rotating open rotors, or most of the marine propeller which operates in the wake of the ship. Therefore there is a need for studies by which the noise from the propeller in a non-uniform flow can be predicted theoretically and experimentally tested.

In this thesis, a propeller noise formulation in the frequency domain is derived from the Formulation 1 of Farassat. It includes loading and thickness noise. The feasibility of measuring marine propeller noise by wind tunnel instead of a water tunnel is studied. A Mach number scaling law of noise generated by a propeller in uniform flow is presented. Using this law, a marine propeller noise has the potential to be measured in a wind tunnel with a model propeller when the flow is uniform. However, the blade vibration caused by the non-uniform water stream may introduce a source that is hard to replicate in a wind tunnel.

The noise from a propeller in the wake of an airfoil is experimentally studied. Before the main experiments, the acoustic wind tunnel was calibrated in terms of aerodynamics and acoustics. Then in this airfoil-propeller interaction set-up, the upstream airfoil modifies local downstream wakes, which further impinge the downstream propeller, leading to an increased noise level compared to the clean set-up with an isolated propeller. A two-component particle image velocimetry (PIV) measurements and far-field acoustic pressure measurements are performed simultaneously. In particular, the velocity field between the stator and the blade of a propeller was measured using PIV. Then, the conventional beamforming technique in aeroacoustics is slightly adapted to locate the sources of the corresponding aerodynamic sound. An increase in the overall propeller noise of about 3 dB was observed, along with the increase of high harmonics of the blade pass frequency tonal noise, when the airfoil is installed.