High speed rotor noise due to blade loading
Abstract
An equation for the far field radiated sound due to dipole sources, which results from blade loading, is derived using the theories of Lowson (1965) and Ffowcs et. al. (1969). The power spectral density (PSD) of the pressure field in a far field is analyzed. The effects caused by the Doppler shift in the amplitude and in the PSD of load fluctuations are considered. The equation relates the PSD of a timedependent dipole strength to the PSD of the pressure fluctuation in the distant radiation field. The theory is employed to study fan noise, and a modified form of the Gutin theory of propeller noise is developed. The application of the data to the prediction of helicopter rotor noise and broadband noise is discussed.
 Publication:

Thermophysical Aspects of Reentry Flows
 Pub Date:
 July 1986
 Bibcode:
 1986aiaa.confQ....D
 Keywords:

 Aeroacoustics;
 Aerodynamic Loads;
 Aerodynamic Noise;
 Fan Blades;
 High Speed;
 Rotor Speed;
 Broadband;
 Far Fields;
 Mathematical Models;
 Acoustics