Acoustic metafluids made from three acoustic fluids

TL;DR

This paper proposes a method to significantly reduce acoustic signatures by surrounding objects with layered shells made of three different acoustic fluids, optimizing their properties for effective sound steering.

Contribution

It introduces a novel design of multi-layered acoustic shells using three fluids with optimized densities and compressibilities to enhance sound steering and radiation reduction.

Findings

Nearly optimal results with specific fluid density configurations.

Simulations demonstrate effectiveness in 2D and 3D.

Discussion on limitations of two-fluid metafluids.

Abstract

Significant reduction in target strength and radiation signature can be achieved by surrounding an object with multiple concentric layers comprised of three acoustic fluids. The idea is to make a finely layered shell with the thickness of each layer defined by a unique transformation rule. The shell has the effect of steering incident acoustic energy around the structure, and conversely, reducing the radiation strength. The overall effectiveness and the precise form of the layering depends upon the densities and compressibilities of the three fluids. Nearly optimal results are obtained if one fluid has density equal to the background fluid, while the other two densities are much greater and much less than the background values. Optimal choices for the compressibilities are also found. Simulations in 2D and 3D illustrate effectiveness of the three fluid shell. The limited range of acoustic metafluids that are possible using only two fluid constituents is also discussed.