Beam Diffraction by the Tip of a Cone and Creeping Beam Waves: Phenomenology Analysis via the Generalized Complex-Source Method

The complex-source (CS) method in conjunction with the spherical-multipole analysis is used to explore and demonstrate the different local phenomena associated with beam-wave scattering by acoustically hard or soft circular cones. The illumination by a beam allows a selective excitation of the scattering phenomena which include reflections, tip diffraction, and creeping beam-waves, where all of them coalesce in the vicinity of the tip. These phenomena depend on the beam's direction and width, on whether the incident beam is converging or diverging as it hits the scatterer, and on whether the scattering point is within or beyond the beam collimation zone. A generalization of the CS method is introduced that can address converging beams. Special emphasis is given to identifying and explaining the footprint of the local diffraction phenomena. All the numerical details are provided so that the reader can readily explore the problem further. For interested readers, supplementary videos are available on IEEE DataPort that give further insight into wave physics and clarify the direction of wave propagation.