阻抗匹配型水下声传播调控超材料器件的设计与验证

Acoustic metamaterials are artificial structures which can obtain some extraordinary acoustic parameters that cannot be realized using natural materials. These unique properties provide possibilities to manipulate the propagation of acoustic waves. So far, researches on underwater devices based on acoustic metamaterials mainly focused on adjusting the effective refractive index while the impendence was not considered. However, reflections caused by the mismatch of the impedance may bring extra disturbance and reduce the energy transmission efficiency. Referring to our previous experiences in the airborne impendence-matching acoustic bend and underwater devices, we propose a method of adjusting the effective bulk modulus and the effective density simultaneously by using composite metamaterial structures in this project. Moreover, a theoretic coupled model will be analyzed when interactions between different components of structures are taken in account. Based on these theories, impendence-matching devices aimed at manipulating the sound propagation in water will be designed and fabricated, such as the underwater bend and the acoustic carpet cloak. Additionally, both simulations and experiments will be investigated to verify the efficiency of proposed devices. Considering the importance and practicability of the impendence-matching devices, this work will explore the basic physical mechanism of underwater metamaterial structures and characterize the acoustic wave propagation coupled with devices. These will contribute to the theory system of underwater metamaterials and find potential practical applications in underwater communications or detections.

声学超材料由于广泛灵活的参数调控能力而被大量运用于声传播调控器件设计中。然而，目前基于超材料的水声器件研究主要集中在等效折射率调控，忽略了器件与背景材料间及器件内部的阻抗匹配。阻抗不匹配导致的能量反射，会对器件工作效率产生较大影响。基于申请者之前对空气声阻抗匹配型超材料器件和水下声传播调控器件的研究经验，本项目提出利用复合结构声学超材料协同调控等效密度与等效体积模量的研究思路，通过研究不同超材料结构单元之间的耦合理论模型，掌握并实现奇异等效声学参数的结构构造与单元组合方法。在理论机理研究基础上，本项目还将设计、制备阻抗匹配的声学弯管、声学隐身毯等水下声传播调控超材料器件，并进行实验验证。在声学器件设计中，阻抗匹配将大幅降低界面处的声反射，提高工作效率，因此本项目研究不仅有助于加深和拓宽人们对水下声学超材料的物理机理认识，还能够为水下声学超材料走向实际应用提供理论基础和技术储备。

声学超材料由于广泛灵活的参数调控能力而被大量运用于声传播调控器件设计中。然而，目前基于超材料的水声器件研究主要集中在等效折射率调控，忽略了器件与背景材料间及器件内部的阻抗匹配，这种阻抗不匹配导致的能量反射，会对器件工作效率产生较大影响。本项目针对这一问题开展深入研究，提出了基于Biot流体与五模材料两种机理的水下超材料等效密度与等效体积模量的独立调节方案，并利用所获得的密度与体积模量独立调节能力设计出具有各向异性密度、各向异性体积模量等多种奇异声学参数的阻抗匹配水声超材料；在超材料单元的研究基础上，通过建立超材料结构单元之间的耦合理论模型，研制出包括基于五模材料的水下声学隐身毯、五模材料型涡旋波水下复用声通讯超表面、基于合成泡沫的阻抗匹配型水下声学隐身毯、宽频水气阻抗匹配层等阻抗匹配型水下声传播调控超材料器件。本项目研究所取得的水下超材料设计方法有助于加深和拓宽人们对水下声学超材料的物理机理认识，同时所研制的阻抗匹配型超材料器件在水声通信、海底目标声隐身等方面有着重要的应用前景。

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