基于主动声学超材料的圆柱声隐身斗篷设计研究

Research on a cylindrical cloak with active acoustic metamaterial layers

基于多层复合材料结构的二维卢隐身斗篷设计思想,利用主动隔膜声学空腔有效密度可以任意控制这一特性,设计了主动声学超材料下的无限长圆柱声隐身斗篷.给出了主动隔膜声学空腔单元的声电元件类比模拟电路图和具体的有效密度控制方法.进行了主动声学超材料声隐身斗篷的结构建模,并对平面入射波入射下此圆柱隐身斗篷周围声压分布场进行仿真计算.结果表明,平面波在一定频率范围内可以毫无阻碍地透过圆柱斗篷,似乎不存在这种障碍物,达到声隐身效果.同时,计算了主动卢材料斗篷下总散射截面随频率变化曲线,研究了此斗篷隐身效果随频率的变化特性.本文从主动控制角度探讨实验实现隐身斗篷的技术问题,有望给卢隐身斗篷实验设计提供一条新的技术途径.

Enlightened by the tunable properties of effective density of the active acoustic metamaterial, we design an active infinite cylinder acoustic cloak according to the idea of the multilayer structured acoustic cloak with homogeneous isotropic materials. Utilizing the electrical analog, the dynamical equation of the acoustic cavity with Piezo-Diaphragm is presented. By analyzing the circuit diagram, the control strategy of achieving various effective densities which are used for constructing the acoustic cloak is given. Based on the necessary parameters such as the wide range values of the relative densities gained by active control, and the acoustic speed of each composite layer, the acoustic pressure field of the plane wave incident on the cloak is calculated, via the FEM model. Also the pressure map of a rigid cylinder scatterer with surrounded fluid is performed for comparison. Results show that outside the cloaking shell, the plane wave field is almost undisturbed. However inside the shell, the plane wavefronts are gradually deflected, and guided around the cloaked domain, returning to the original plane shape with small perturbation. This phenomenon making the cloak acoustically invisible in some frequency ranges has useful values in engineering applications. Finally, the total scattering cross section of the cloak is calculated to investigate the invisible effect according to the frequency domain. The total number of the composite active metamaterial layers is 15, which is much easier to realize in experiment.