Acoustic Extraordinary Refraction In Layered Sonic Crystals With Periodic Slits And Manipulating Microparticle Based On Metamaterial In Air

Phononic crystal(PC) can manipulate flexibly the sound waves. In the early stage,the researchers mostly focused on the study of phononic band gaps. With the development of phononic crystals and deepening of the study on PCs, the researchers gradually transfer from studying the band gaps of conventional PCs, to focus the properties of conventional PCs and the development of new acoustic crystal devices by utilizing the PCs. In recent years, as development of optical-metamaterial,sound-metamaterial has become the topic. In this dissertation, by using the finite element method we mainly study the acoustic refraction of traditional acoustic phononic crystal, and the trapping for microparticle based on acoustic metamaterial.The main works involved in this dissertation are as follows:Firstly, we present a study of acoustic wave propagation in layered sonic crystals(SCs) with periodic slits, and demonstrate the extraordinary acoustic refractions induced by acoustic backward and forward wave effects in SCs. By tuning the parameters of geometry structures and incident angles of acoustic waves, the positive,negative and zero acoustic refraction are demonstrated respectively. Taking advantage of the exotic acoustic refraction, we present the splitting of acoustic beams through the layered SCs, which is a new method to achieve acoustic beam splitting including the phenomenon of two and three beams.Secondly, we use the deeply sub-wavelength holey structure metameterial to achieve trapping microparticles and the resonant mode is Fabry-Pérot resonance through the analysis effective of medium theory and band structure. We use the second order Fabry-Pérot resonance frequency corresponding to the local sound field and analyze the distribution of force field above the acoustic crystals surface to verify that the deep sub-wavelength holey plate metameterial can trap microparticles in the space where is around 40 um from surface.Lastly, we analyze the resonance mechanism of zig-slit acoustic metameterial which is Mie resonance, and show that highly localized sound fields and the mode of monopole resonance can be induced by optimizing the geometrical parameters of the material,by analyzing the magnitude and direction of acoustic radiation force which is suffered by microparticle in the space, aggregation of the fine particles in the air is achieved.