Broadband Transformation Acoustic Waveguide With Anisotropic Density Based on Pentamode Metamaterials

Xing Chen,Jihong Wen,Li Cai

doi:10.3389/fmats.2022.860126

Abstract

Multiple layer anisotropic fluid medium is critical to the realization of transformation acoustic devices, such as cloak or bend waveguide. Pentamode metamaterials have attracted extensive attention as a solid artificial version with anisotropic modulus to approximate liquids. In this paper, we present an approach to realize fluid-like anisotropic density by using pentamode materials, and an underwater bend acoustic waveguide with anisotropic density is designed and fabricated to demonstrate the effectiveness of it. Simulation results indicate that, compared with anisotropic-modulus design by using pentamode materials, wider bandwidth acoustic modulation effect can be obtained. An in-depth and comprehensive analysis of the mechanisms of the broadband characteristics is provided by calculating the band structure of the pentamode metamaterials constituting the acoustic waveguides and analyzing their vibration modes. Finally, remarkable wavefront manipulation for underwater acoustics based on the acoustic waveguide with anisotropic density is experimentally verified.

Highlights

Acoustic metamaterials are artificial periodic structures with subwavelength scales that exhibit extraordinary acoustic properties (Liu et al, 2000; Norris, 2009; Assouar et al, 2018), such as negative mass density or modulus (Ding et al, 2007; Huang et al, 2009; Liu et al, 2011; Xu et al, 2020), negative Poisson’s ratio (Burns, 1987; Bertoldi et al, 2010; Li et al, 2017), and anisotropic density or modulus (Torrent and Sánchez-Dehesa, 2008; Wu et al, 2012; Kutsenko et al, 2017)
Acoustic devices designed based on transformation acoustics generally contain material properties that are almost impossible for us to obtain in nature, such as sharp gradient changes, anisotropic modulus or anisotropic density, which greatly hinders the manufacture of such acoustic devices
The geometric configurations of pentamode microstructures with anisotropic modulus tend to be complex, which brings many difficulties to the design and application of acoustic devices with anisotropic modulus. Since both the mass density and modulus of a medium affect the dynamics of acoustic wave propagation, directing acoustic waves to propagate in a curved path can be achieved by materials with anisotropic modulus, and by materials with anisotropic density

Summary

INTRODUCTION

Acoustic metamaterials are artificial periodic structures with subwavelength scales that exhibit extraordinary acoustic properties (Liu et al, 2000; Norris, 2009; Assouar et al, 2018), such as negative mass density or modulus (Ding et al, 2007; Huang et al, 2009; Liu et al, 2011; Xu et al, 2020), negative Poisson’s ratio (Burns, 1987; Bertoldi et al, 2010; Li et al, 2017), and anisotropic density or modulus (Torrent and Sánchez-Dehesa, 2008; Wu et al, 2012; Kutsenko et al, 2017). The advent of the pentamode material allows the density and modulus of the material to be flexibly adjusted within a certain range, which latently provides an access to physical realization of such acoustic devices (Layman et al, 2013; Sun et al, 2019) With this method, pentamode acoustic cloaks are designed using fluidlike pentamode microstructures with anisotropic modulus (Scandrett et al, 2010; Chen et al, 2015). The geometric configurations of pentamode microstructures with anisotropic modulus tend to be complex, which brings many difficulties to the design and application of acoustic devices with anisotropic modulus Since both the mass density and modulus of a medium affect the dynamics of acoustic wave propagation, directing acoustic waves to propagate in a curved path can be achieved by materials with anisotropic modulus, and by materials with anisotropic density. An acoustic waveguide with anisotropic-density is fabricated and the experiment is conducted to verify the effectiveness of this waveguide for manipulating underwater acoustic waves

DESIGN AND PERFORMANCES OF ACOUSTIC WAVEGUIDES

CONCLUSION

DATA AVAILABILITY STATEMENT