Acoustical Scattering by Multilayer Spherical Objects Containing Electrorheological Fluid

Abstract

Scattering is the most fundamental problem in the research on phononic crystals and acoustic metamaterials; and scattering in a three-dimensional space poses challenging issues; and yet, the most challenging of all, is the scattering by elastic objects since an acoustic wave splits into different types of waves, propagating at different speeds, when it enters an elastic object. In this paper, a unified formalism is developed to analyze the scattering of an acoustic wave by a multilayer spherical object that is made of a mixture of an arbitrary number of concentric layers of elastic and acoustic media. Using this formalism, acoustical scattering by a multilayer spherical scatterer encasing an electrorheological (ER) fluid layer in an underwater environment is studied. Numerical examples show that ER fluids can alter the scattering characteristics above the first resonant frequency, which itself can be tuned by the applied electric field.