Research on Acoustical Scattering, Diffraction Catastrophes, Optics of Bubbles, Acoustical Phase Conjugation, and Wake of an Oscillating Circular Cylinder.

摘要

The research summarized concerns several aspects of the propagation and scattering of acoustical and optical waves. The topics discussed fall under the following five categories: A. Project to extend GTD (Ray methods) to guided waves on smooth elastic objects in water as tested by synthesis of the forward and backward scattering amplitudes of a spherical shell and the total scattering cross section. B. Acoustical and optical caustics and associated wavefields: opening rate in the transverse cusp in light scattered from oblate water drops; scaling laws and wavefront shape for light backscattered from oblate drops. C. Physical optics of bubbles in water: an asymptotic series for critical angle scattering useful for determining bubble sizes. D. Acoustics phase conjugation and aspects of wavefront reversal: the present status of experiments on three-wave mixing in a layer of microbubbles in water; and preliminary aspects of an experiment with phase conjugation of ripples on layer of water. Response of the wake of a circular cylinder to forced torsional oscillations: waves on shear layers and effects on primary and secondary vortices.(JHD)