流体基中单层圆柱/圆球人工结构中的非泄漏声表面波及波导特性研究

The recent research on artificial surface acoustic wave（SAW） has attracted widespread interest in the research field of acoustic artificial structure. However the current mentioned mechanism of artificial surface acoustic wave is mostly based on acoustic waveguide mode in the subwavelength hole/slit in rigid plate or the collective diffraction effect based on periodic subwavelength grooves/ridges without openings. Recently by studying the Dispersive line caused by the structure of monolayer solid cylinder/ball immersed in fluid background, we found that this artificial nonleaky surface acoustic wave which performed like Lamb wave could be supported by that structure, meanwhile different from the previous studies, this kind of surface acoustic wave is originated from the scattering of a single cylinder. Firstly, we intend to study dispersion line of the system with high acoustic impedance ratio (steel water / air) and the scattering matrix of a single cylinder, and analyze the utility of different scattering channels on the surface wave then find out the key physical quantities. Secondly we intend to discuss the scattering properties of single cylindrical in the system with low acoustic impedance ratio. For the existence of Stoneley wave on the solid-fluid interface, the physical mechanism of non leaky surface acoustic wave acoustic in the system is more abundant, which is helpful for the design of deep subwavelength surface acoustic wave by using higher order scattering characteristics. Finally we want to use this kind of surface acoustic wave to design high efficient acoustic waveguide, and through the design of artificial structure to realize the controllable propagation of waveguide in direction and spatial position. The research of this project will help to put forward a new mechanism of artificial surface acoustic wave, and with the theoretical value and application prospect.

近年来人工声表面波的研究在人工结构领域引起广泛兴趣。但目前提出的人工声表面波基本都是基于声学平板上亚波长孔/缝结构中的声波导模式或是板上周期性突起/凹槽的集体衍射效应。最近申请人通过研究流体基中单层钢柱的色散线，发现这种非联通人工结构能够支持类似Lamb波的非泄漏表面波模式，且与以往不同的是这种模式源于单个圆柱的散射。本项目首先拟通过研究高声阻抗比体系(钢-水/空气)的色散线及单个圆柱的散射矩阵，分析不同散射通道对该表面波的作用，找出关键物理量；其次拟讨论低声阻抗比体系中单个圆柱的散射特性对非泄漏声表面波声物理机制的影响，低声阻抗系统中固-液界面上存在的Stoneley波使得单体散射特性更加丰富，有助于利用更高阶散射特性实现深亚波长声表面波的设计；最后拟利用这类声表面波设计高效声波导，并通过设计人工结构实现其传播方向和空间位置的可控。本项目的研究有助于提出新的人工声表面波机制，预期新应用。

基于课题组在人工声学材料、超表面等方面已有的研究成果，本项目主要围绕两方面开展研究。一方面研究人工声学材料中的新型声表面波导特性、高效阻声及声学分束特性：研究周期排列钢柱-水/空气结构中的非泄漏兰姆波模式和波导特性，实现高效声表面波导传输；研究了钢/水二组元体系中泄露的兰姆波的激发效应，实现反对称泄露兰姆波的单向激发；利用空气圆柱/钢/水复合二维结构，在水基体中实现高效隔声效应；设计了一个新颖的有限尺度二维钢/水声子晶体实现了声学分束。另一方面围绕利用人工设计结构实现有限衍射声束及声场中对颗粒操纵方面进行了探索和实验研究：人工设计了两种声超表面结构，能够分别实现将入射的高斯声束转化为二维的半贝塞尔声束和声涡旋束；设计制备了梯度变化的一维钢/水体系声人工结构板，实现了可移动的声场和粒子往返运动操控；研究了一阶及二阶涡旋声束对不同形状固体材料的力矩效应，实现了同一工作频率下的一阶及二阶贝塞尔束；设计并制备二维正方排列的周期孔分布（孔中填充软树脂）的结构板，利用声人工结构中的周期局域声场实现胶囊型颗粒的捕获。本项目的研究有助于提出新的人工声表面波及声波场操控的机制，为新型声波器件设计提供新思路。