Based On The Singular Medium Of Acoustic Ultra-scattering With The New Cloak Design And Research

In this thesis,we design and investigate two kinds of novel acoustic devices using acoustic metametarials:two-dimensional acoustic superscatterers and two-dimensional novel acoustic cloak that can cloak "external" objects.These two kinds of acoustic devices can accomplish functions which are absent in the traditional acoustic devices, and can find some interesting applications.Our work is based on acoustic metametarials which is considered as novel fruits of material science.The novelty of acoustic metamaterials originates from its artificial elastic composite structure which can enable some exotic material parameters,such as negative anisotropic dynamic mass density and negative bulk modulus,beyond that of natural materials.Due to such exotic material parameters,we could design some novel devices which break the limits imposed by traditional materials,theoretically and functionally.This thesis can be divided into the following chapters:In the first chapter,we present some brief introduction to metamaterials.At first, we give the acknowledged definition of metamaterial which poses a novel concept in material science before the history and applications of electromagnetic metametarials are discussed.Then we shift emphasis on the mechanism behind acoustic metamaterials, and by comparing the development of devices based on electromagnetic metamaterials to those based on acoustic metamaterials,we point out there are numerous yet meaningful works to be done in the field of acoustic metamaterials based devices, and the existing results of electromagnetic metamaterials based devices can essentially facilitate the research of its acoustic counterparts.In the second chapter,we firstly present the concept of complementary media, then introduce a novel device named "acoustic superscatterer",which utilizes acoustic complementary media and scatters more waves than it appears.The fundamental process of theoretical design of acoustic superscatterers lie on the deduction of material parameters of the metamaterial layer in the devices,which is fulfilled by generalization of transformation optics in the scenario of electromagnetic metamaterials based design, to acoustic cases.Both the two-dimensional circular and rectangular design are given, simulated by using finite element solver,and verified thoroughly.Then some potential applications and the difficulty in their experimental realization are discussed.In the third chapter,we firstly present the essential drawback of traditional acoustic cloaks by which the cloaked objects are "deafened".Then we generalize the newest advance in electromagnetic cloaks,namely using "anti-object" to cloak "external" objects, to the case of acoustic cloaks,conquering the drawback of existing designs by allowing receival of incoming waves by the cloaked objects.The geometrical configurations, deduction of material parameters and simulations are borrowed from existing works of designing superscatterers in the second chapter,and the simulation results clearly demonstrate the strength and performance of our design.