Multipole reasonances in elastic wave-scattering from cavities and in acoustic wave-scaterring from bubbles and droplets

Abstract

By means of the Resonance Theory of viscoelastic wave-scattering from cavities in solids, we examine several multipole contributions to the sonar cross sections of fluid-filled cavities in solid rubbers. The analysis is done first ignoring, and then accounting for mode-conversion in the solid rubber matrix. The results are analytically particularized to the simpler cases of a) the nth multipole of a gas-bubble in water, b) the nth multipole of a liquid droplet in a gas, c) the zeroth order multipole (i.e., monopole) contribution for a gas-filled cavity in solid rubber. Results for other multipoles are then numerically examined and displayed, up to the quadrupole case. The program we have developed can generate similar results for any higher-order multipole and any combination of substances, in any of the above situations.