Green’s Functions Technique – Moving Sources
The formal solution of the linear wave equation is provided by Green’s function technique, fully described in many handbooks of acoustics and more specifically by Goldstein (1976). This background is shortly reminded here for the sake of completeness. The wave equation describes all prob-
Figure 6. Academic exercise: scattering of a lateral
quadrupole by a cylinder. Instantaneous pressure maps up to a distance of 5 wavelengths from the cylinder axis.
lems in mathematical physics in which the effect of some scalar quantity propagates with a finite speed. Aeroacoustics is just a special case in which the sources are related to unsteady flow features. Therefore source motion
is first analyzed here from the more general standpoint of the wave equation itself, and later specified to monopole, dipole and quadrupole acoustic sources. This will highlight the specific nature of acoustic sources.