可调式局域共振声学材料的水下声学特性研究

The underwater acoustic material has enormous military and civilian demand, such as the noise control of ships and marines, or the acoustic equipment of underwater experiments. However, the traditional acoustic material usually has a bottleneck of the bulky thickness or the high-frequency working limit. The locally resonant sonic material (LRSM) has a broad application prospect, since it can control the long-wavelength sound with much smaller structural size. In this project, we propose an adjustable locally resonant sonic material, and investigate its underwater acoustic performance. Such adjustable LRSM consists of multiple independent layers of sliced local resonators, which is immersed in water. It not only has more acoustic mechanisms, but is also more flexible to adjust properties of resonators or structural sizes. The project focuses on the mechanism and regulation of the coupling of band gaps, as well as the acoustic performance of the LRSM under the condition of oblique incidence. Based on these studies, we further propose two scientific applications. The first one is integrating the reflection of band gaps, the mismatch of characteristic impedance and the dissipation of components to design an underwater acoustic shield with broad working frequencies and strong attenuating performance. The other one is employing the imperfect-coupling pass bands or the surface localized modes to perform an underwater acoustic bandpass filter with high noise-signal ratio. Such project does not only hold great academic significance, but also has a promising engineering application. It provides an important theoretical guidance and technical support for the evolution of the underwater acoustic material.

水下声学材料在舰船与潜艇噪声控制，以及水声实验环境搭建等方面有着重要的军事与民用需求背景，然而传统的声学材料大多存在材料厚度大、作用频段高的设计瓶颈。局域共振声学材料由于具有‘小尺寸控制大波长’的优势，因此在水下声学材料的设计中具有广阔的应用前景。本项目创新提出可调式局域共振声学材料，并研究其水下声学特性。该结构由多层相互独立的片状局域共振单元层周期排列浸入水中构成，不仅具有丰富的声学机理，且可灵活地调节单元属性和结构尺寸。项目围绕其带隙耦合作用机理和调控规律，以及斜入射条件下声学特性的变化规律展开深入的理论研究和实验验证，并提出综合利用带隙反射、阻抗失配、阻尼耗散实现宽带、高效的水下隔声屏障，以及利用非完美耦合通带或表面局域态等声学现象实现高信噪比的水下带通声滤波器。该研究不仅具有重要的科学研究意义，且具有很强的工程应用价值，为水下声学材料的应用与革新提供重要的理论指导和技术支持。

水下声学材料在舰船与潜艇噪声控制、水声实验环境搭建等方面有着重要的军事与民用需求背景，然而传统的声学材料大多存在材料厚度大、作用频段高的设计瓶颈。局域共振声学材料具有‘小尺寸控制大波长’优势，在水下声学材料的设计中有广阔的应用前景。本课题通过建立局域共振单元的物理等效模型、材料整体的等效声速模型、周期边界有限元模型，以及统计优化模型为局域共振声学材料吸声、隔声机理分析，以及优化设计提供了理论基础。.利用单元物理等效模型深入讨论了局域共振单元在不同参数和约束条件下的吸声特性，总结出吸声性能优化的参数规律；利用等效声速模型详细分析了局域共振声学材料中局域共振带隙和布拉格带隙的产生和作用机理；研究了通过调整材料参数，拉低材料整体等效声速，进而降低布拉格带隙作用频段的调参方法，并利用参数调整将局域共振带隙与布拉格带隙耦合，进而获得低频宽带的隔声特性。利用课题所提出的可调式局域共振声学材料思路，设计了具有固液交替式基体的局域共振声学材料，通过带隙耦合优化实现没有横波干扰的低频宽带隔声特性；通过对局域共振声学材料斜入射声学特性进行机理分析，弄清了材料参数与其隔声性能斜入射稳定性之间的作用关系，使优化隔声方案不仅在垂直入射条件下能够有明显的低频隔声效果，在斜入射条件下也能保持稳定的隔声性能。.此外，还通过统计优化模型验证了材料吸声与隔声优化规律，并且通过集成声学结构的优化设计获得了低频宽带的吸声材料，通过实验验证该材料在加压条件下依然拥有优异的低频宽带吸声性能，该研究为舰船低频吸声材料的改进应用提供了可行的应用方案。