Acoustic metafluids

TL;DR

This paper introduces acoustic metafluids, fluids engineered to mimic other acoustic properties, highlighting their potential for broadband cloaking through anisotropic inertia and pentamode materials.

Contribution

It characterizes the most general class of acoustic metafluids, linking their properties to anisotropic inertia and pentamode materials, and discusses conditions for isotropic inertia for broadband cloaking.

Findings

Acoustic metafluids can be designed with anisotropic inertia.

Conditions for isotropic inertia enable broadband cloaking.

Energy density transformation underpins the design principles.

Abstract

Acoustic metafluids are defined as the class of fluids that allow one domain of fluid to acoustically mimic another, as exemplified by acoustic cloaks. It is shown that the most general class of acoustic metafluids are materials with anisotropic inertia and the elastic properties of what are known as pentamode materials. The derivation uses the notion of finite deformation to define the transformation of one region to another. The main result is found by considering energy density in the original and transformed regions. Properties of acoustic metafluids are discussed, and general conditions are found which ensure that the mapped fluid has isotropic inertia, which potentially opens up the possibility of achieving broadband cloaking.