Some Aspects of Aeroacoustics: From Rayleigh Until Today

Abstract

An overview of aeroacoustics is provided, beginning with a discussion of the properties of point sources of sound of various orders. This is followed by treatment of the sound generated by a free aerodynamic flow (in the absence of rigid surfaces), and finally by a discussion of the effects of surfaces—very small (aeolian tones), very large (boundary layers), and the important effect of the edge of a large surface (trailing edge noise). In the first part, it is assumed that the aerodynamic flow is given, and that the sound produced by the flow does not act on the flow itself. In the second part, there is a reaction on the flow, and the effect is first order. Then a flow resonance occurs, even though no physical resonator is present; and of course, a physical resonator can be present, as in the familiar case of the organ pipe.