RESUMO
A tonal thickness noise and loading noise model of rotating blades has been developed as an extension of the exact frequency-domain solutions for rotating monopole and dipole point sources. The present model has two advantages over the previous methods and models for noise prediction. The first is the unified expression for sources in subsonic and supersonic rotation even at rest. The second is that the present model has no limit on the location of the observer and no interpolation error. Two test cases are carried out to validate the present model and emphasize its advantage at the noise prediction for sources in supersonic rotation. Moreover, as a specified application of the present model for the rotating blades whose tip radius is acoustically compact, acoustic energy distribution at different frequencies and in different directions is analyzed. Result shows that the acoustic energy of acoustically compact rotating blades is mainly concentrated at the source frequency while propagating along the axial direction, leaving the rest propagating along the radial direction at the other frequencies.
RESUMO
An exact solution of the acoustic field around the rotating dipole source has been derived by using a series expansion method and the gradient calculation in the spherical and cylindrical coordinate systems which extends a previously published solution for a rotating monopole source. The proposed exact solution establishes an analytical method to predict the sound radiated from the rotating blades once the acoustic sources have been known.