基于声学黑洞效应（ABH）的波操纵及其工程应用中的力学问题研究

The fundamental nature of all vibration and acoustic phenomena in engineering structures, such as aircraft, spacecraft and ocean vessels, is wave motion. Futhermore, wave manipulation, such as change of propagation path, focusing, trapping and damping, is the foundation for vibration and noise suppression in these structures. Hence, wave manipulation starts to draw the ever-increasing attention in the scientific community. The development of the so-called acoustic meta-material is just one of the typical examples to evidence the effort that people are making in manipulating waves such as optical or acoustic waves. Acoustic Black Hole (ABH) is another phenomenon which starts to arouse the interest of the vibration community primarily during the last decade. ABH effect takes advantages of the propagation properties of the structure-borne waves in thin-walled structures. By reducing the wall thickness according to a power-law profile, the local phase (and the group) velocity of the flexural waves gradually reduces, theoretically approaching zero reaching the wedge end. In an ideal scenario, this results in zero reflection and total energy absorption with a small amount of damping materials. . Despite the past effort, the research, as well as the exploration of the ABH, is still in its infancy. Two fundamental scientific problems need to be solved in order to push the ABH-based technology to the next level: 1) Understanding of the wave trapping process of the ABH, especially in the presence of geometrical and fabrication uncertainties, is insufficient. 2) The crucial issue of the coupling between the ABH and the damping layer coating is not well apprehended by the existing models. Bothe issues hamper the design and realization of the ABH effect in practice. In terms of engineering applications, structure-borne noise control based on ABH feature is also a new topic which has not been fully explored. Meanwhile, the design issue of effectively producing the ABH effect while ensuring the mechanical rigidity and integrity of the structure also needs to be tackled before the ABH technique can find more real-world engineering applications.. The general objective of the project is therefore twofold. From the basic research viewpoint, this project attempts to provide solutions to the two aforementioned fundamental problems. From engineering application viewpoint, the feasibility of manipulating structure-borne energy for sound radiation and transmission control, along with the understanding of the underlying physics, will be explored. Meanwhile, we shall examine various ABH designs to suit engineering applications. The significance of the project lies in its direct applicability to a wide range of noise control and energy harvesting problems. In a broader sense, the problem under investigation is fundamental and generic in nature, which has significant scientific value for advancing the state-of-the-art in vibration and noise control engineering.

航空航天飞行器、舰船等大量工程结构中的声振现象的共性本质是波动，而实现这类结构减振降噪的一个共性基础正是波的操控。声学黑洞是通过薄壁结构厚度或者材料特性的梯度变化，实现波的减速、聚焦等操控。本项目主要研究基于声学黑洞的工程结构中波操控的力学问题，此研究是学科前沿，不仅具有重要的科学意义，而且直接与工程中的声振问题和能量回收技术相结合，具有广阔的应用前景。在前期力学建模和控制等相关研究的基础上，探究结构中的声学黑洞效应。建立研究此类结构波传播与操控问题的建模和分析方法，重点探索声学黑洞现象的特征行为和波传播演变过程。揭示声学黑洞现象背后的物理机制，深刻认识声学黑洞结构在多物理场耦合情况下各参数的影响规律。积极拓展声学黑洞结构在减振降噪、能量回收等工程领域中的应用，发现声学黑洞的声辐射机制和多物理场耦合能量聚集效应，提出结构优化设计方法，满足工程实际应用。

针对声学黑洞ABH波操控方法的学术前沿，以及高效设计ABH结构相关研究还很匮乏的现状，本项目围绕声学黑洞的建模、分析、评价、应用等开展了研究。建立了基于小波基-拉格朗日法的ABH能量耦合模型，设计了基于激光超声非接触式的波场能量时频域实验方法，提出了基于程函方程的波轨迹数值分析方法，揭示了二维ABH效应的形成机制，解决了传统模型难以高效分析全耦合影响的难题，快速实现了复杂二维ABH结构中波传播路径的追踪和能量聚集位置的预测。明晰了非理想ABH结构全耦合下参数对弯曲波操控效率的影响规律，获得了最优结构设计方案和附加元件的布置方式，提高了能量聚集和耗散效率；建立了基于模态空间和波数域的两种ABH封闭声腔的声振耦合模型，阐明了局部模态降低ABH有效作用频率的现象，发现了ABH声振解耦的特殊优异功能，解释了ABH实现降噪的内在机理。建立了一维反射系数和二维功率流法能量光斑的评价方法，实现了能量聚集效果的定量评估。提出了复合式、非理想等多种ABH新构型，不仅提升了结构的强度，提高了能量聚集效应，而且丰富了ABH结构优化设计的可调节参数；发明了阵列式ABH、多维动力吸振ABH等结构形式，阐明了结构尺寸、位置、维度等参数对控制效果的影响规律，不仅有效解决了强度与频率之间的矛盾，而且克服了传统ABH可调频率范围窄的不足。以直升机和航天结构为对象，设计了圆盘式、内嵌式等ABH减振降噪结构，以及一维和二维能量回收系统，获得了在装备结构减振降噪、能量回收中的应用，取得了良好效果。ABH的研究不仅丰富了波操控理论，为后续设计和优化ABH结构提供了理论依据，且促进了ABH结构在工程减振降噪和能量回收中的实用化。发表论文67篇，其中29篇SCI（另三篇在一修中），10篇EI；获国家发明专利8项；获国防科技发明二等奖、江苏力学科技一等奖各1项。培养博士生11名，硕士生8名。培养青年教师一名，破格成为教授，并获得国家优青。举办国际会议2次，国内会议1次。做大会报告、邀请报告等20余次。