声学栅修饰声子晶体及周期固体板特性研究

发布时间：2018-10-05 10:19

【摘要】：声子晶体(Sonic Crystal,SCs)具有丰富的色散关系,可以人为地设计带结构,实现声波的独特传播,广受人们关注。随着研究的发展,具有单一功能的声学器件逐渐不再满足人们的需求,为了满足声学集成的需要,人们开始研究声子晶体和其它声学器件的复合,以及它们结合所产生的新现象和特性。而本文主要关注点之一就是声学栅与声子晶体的复合系统。同时声学表面结构是文章涉及的另一种研究对象,这类的研究始于结构表面波(designer surface waves)的实现。在研究过程中反常透射、反常反射和反常折射都被人们证实,并且展现了一些其它独特的性质和优点,逐渐地成为了声学研究的新热点。通过求解弹性波方程和利用有限元软件进行数值模拟,本文主要关注了声学栅与声子晶体的复合系统某些功能器件的设计和声学表面结构电磁学现象的声学类似。具体来说,本文的工作主要涉及以下几个方面:首先在第二章中,基于声学栅修饰的二维声子晶体,我们分别分析了完美声子晶体的相空间、对称复合系统的相空间、非对称系统的相空间。计算结果表明,通过引入不同附加的声学栅结构,我们在晶体界面能获得不同横向的波矢增量。更具体来说,引入适当的对称声学栅,可以很好地改善完美晶体禁带的能量通透性;引入非对称栅结构,我们获得了一种较为新颖的分束装置。随后在第三章中,进一步研究了这个复合系统,进行一些功能设计:第一,通过不对称声学栅打破晶体两侧的空间对称性,合理的设计其结构,实现了声波的不对称传播设计;第二,实现了一个较为高效地传播声波向表面波的转换装置;第三,通过附加声学栅结构改善了整个系统的色散关系,在高对称点周围,获得等效微量负折射形成的高品质定向自准直束。最后在第四章,利用在刚性固体板表面刻上周期的亚波长凹槽,获得了结构表面波。引入一个小的梯度,分别计算了它们的色散关系:它们全部处于水线以下,表明了其非泄露的特性,并且随着凹槽深度的增加,表面波越来越偏离基体线,越来越局域在固体板表面;同时随着凹槽深度的增加,它对应的截止频率逐渐减小。由此,我们设计引入一个凹槽深度线性增加的结构,结果显示在垂直固体板表面方向,声波越来越贴近固体板;在沿表面方向,声波传播距离越来越短。最终设计实现了一个类“电感”器件。
[Abstract]:Phonon crystals (Sonic Crystal,SCs) are widely concerned because of their rich dispersion relationships and the artificial design of band structures to achieve the unique propagation of sound waves. With the development of research, acoustic devices with a single function gradually no longer meet the needs of people. In order to meet the needs of acoustic integration, people began to study the combination of phonon crystals and other acoustic devices. And the new phenomena and characteristics produced by their combination. One of the main concerns in this paper is the composite system of acoustic grating and phonon crystal. At the same time, acoustic surface structure is another kind of research object, which begins with the realization of structural surface wave (designer surface waves). Anomalous transmission, anomalous reflection and anomalous refraction have been confirmed in the course of the study, and have shown some other unique properties and advantages, which have gradually become a new hot spot in acoustic research. By solving the elastic wave equation and using the finite element software for numerical simulation, this paper focuses on the design of some functional devices of the composite system of acoustic gate and phonon crystal, which is similar to the acoustical surface structure electromagnetic phenomenon. In the second chapter, we analyze the phase space of perfect phonon crystal and the phase space of symmetric composite system based on the two dimensional phonon crystal modified by acoustic grating. The phase space of an asymmetric system. The calculation results show that we can obtain different transverse wave vector increments at the crystal interface by introducing different additional acoustic gate structures. More specifically, the energy permeability of the perfect crystal band gap can be improved by introducing a proper symmetrical acoustic gate, and a novel beam splitting device is obtained by introducing the asymmetric gate structure. Then in the third chapter, the composite system is further studied and some functions are designed. Firstly, the asymmetric acoustic grating is used to break the spatial symmetry on both sides of the crystal, and its structure is reasonably designed to realize the design of asymmetric propagation of sound wave. Secondly, a conversion device for transmitting acoustic wave to surface wave is realized. Thirdly, the dispersion relation of the whole system is improved by adding the acoustic grating structure, which is around the high symmetry point. A high quality self-collimating beam with equivalent trace negative refraction was obtained. Finally, in chapter 4, the structural surface waves are obtained by using the periodic subwavelength grooves etched on the surface of rigid solid plates. A small gradient is introduced to calculate their dispersion relations: all of them are below the pipeline, indicating their non-leakage properties, and the surface wave deviates from the matrix line with the increase of the groove depth. At the same time, the cutoff frequency decreases with the increase of groove depth. As a result, we design and introduce a structure with a linear increase in groove depth. The results show that the sound wave is closer to the solid plate in the vertical direction of the surface, and the propagation distance of the sound wave is getting shorter and shorter in the direction of the surface. Finally, a kind of inductor device is designed and implemented.
【学位授予单位】：吉首大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O735

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