Acoustic scattering reduction of elliptical targets via pentamode near-cloaking based on transformation acoustics in elliptic coordinates

TL;DR

This paper develops a novel transformation acoustics method using elliptical coordinates to design pentamode cloaks for elliptical targets, advancing underwater stealth technology by enabling better control over material anisotropy and shape adaptation.

Contribution

It introduces an analytical approach using elliptical coordinates for pentamode cloaks, improving shape flexibility and anisotropy control compared to existing methods.

Findings

Analytical design of cloaks for elliptical targets

Enhanced control over anisotropic material properties

Potential for improved underwater stealth applications

Abstract

Cloaks for underwater applications designed for actual submarine acoustic stealth are still far from the technological advancement needed for being put in practice. Several challenges are to be overcame such as dealing with weight or non-axisymmetric shapes. In this paper, we introduce the use of elliptical coordinates to define quasi-symmetric transformations to retrieve the material properties of pentamode cloaks for elliptical shaped targets, along with a quantifiable approximation introduced by the rotation tensor being different from the identity. This is done analitically adopting transformation theory, in an attempt to generalize the usual approach for axisymmetric cloaks, with the aim of dealing with shapes closer to those of the actual cross section of a submarine. With respect to existing techniques for dealing with arbitrarily shaped pentamode cloaks, the introduced technique allows for a priori control on the principal directions of anisotropy and for enlarged design space in terms of possible combinations of material property distributions for the same geometry of the problem.