新型水下耐静压、低频宽带、超薄吸声结构的设计原理和方法

On the basis of new-established theories of Transformation acoustics, Acoustic metamaterials, Phononic crystals, etc., the project proposes a novel design idea and working principle for a underwater acoustic absorbing structure with low-frequency and broadband absorbing performance, large hydrostatic pressure load bearing capacity and ultrathin thickness, and also, a novel underwater acoustic absorbing structure based on the proposed principle is put forward, for the purpose of finding a better solution to the difficult problem for the design of the acoustic coatings of submarine with the low-frequency and broadband absorbing performance and the large hydrostatic pressure load bearing capacity. In principle, (1). Utilizing complex cavity structures, complex channels and anisotropic acoustic materials to converge the acoustic wave, to control its transmitting path, and to guide it propagating along a curved and twisted path in the acoustic absorbing structure, the transmission path length of the acoustic wave in the acoustic absorbing structure will be enormously increased and becomes several dozen times longer than the thickness of the acoustic absorbing structure, as a result, the design of acoustic absorbing structures with ultrathin thickness can be realized easily. (2). Applying the extreme long transmission path of the acoustic wave in the acoustic absorbing structure to arrange the locally resonant element array with distributed resonant frequencies, the low-frequency and broadband absorptive performance of the acoustic absorbing structure can be easily achieved and conveniently designed. (3). Based on the transformation acoustics theory, the effect of the variation of cavity cross section or channel cross section on the acoustic impedance can be eliminated thoroughly by combining the change of the cavity shape and the variation of acoustic material parameters together to control the concentration and propagation of acoustic waves, and the full-frequency band impedance matching design can be achieved in theory. (4). Taking advantage of the hydrostatic load relieving technology and the design method of structural support with quasi-zero tangent stiffness, the influence of the hydrostatic pressure applying to an acoustic material on its absorptive performance of acoustic waves is relieved, and the design of hydrostatic pressure load bearing capacity and the design of acoustic absorbing performance can be separated and considered independently in the design procedure of acoustic absorbing structures. In this project, the theory and method for the acoustic characteristics analysis of the novel underwater acoustic absorbing structure will be investigated, and also, the optimization design theory and method of the novel underwater acoustic absorbing structure will be researched and constructed. Meanwhile, according to the real need of submarines and aiming at bearing pressure with 3MPa—5MPa, lower limit of absorbing frequency band under 300Hz, the relationship between the structure parameters of the novel underwater absorbing structure and its performance parameters will be analyzed and investigated by virtue of numerical simulation method, and the testing model of the novel underwater acoustic absorbing structure will be designed and fabricated.

为解决潜艇声学覆盖层结构低频宽带吸声且耐静压的设计难题，结合变换声学、声学超材料和声子晶体等新理论，构思并提出一种新的水下吸声结构设计原理和新型水下耐静压、低频宽带、超薄吸声结构。原理上，①通过型腔和各向异性材料控制声波汇聚，使其沿曲线迂回传播，几十倍延长声波的传播路径，增加吸声结构等效厚度，实现超薄设计；②利用声波超长传播路径，布置多频率点局部共振单元，实现低频宽带声波吸收；③应用变换声学理论，通过型腔形状和材料参数变化控制声波汇聚和传播，消除型腔截面变化对声阻抗的影响，实现宽带阻抗匹配设计；④借助卸荷设计和近零切线刚度支撑，消除静水压力对声学材料吸声性能的影响，使吸声结构耐静压设计和吸声性能设计独立。本项目将研究这种新型水下吸声结构的理论分析和优化设计方法，并结合潜艇需求，以耐静压3MPa—5MPa，低频吸声拓展到300Hz以下为目标，数值研究结构参数与吸声性能间的关系，设计制造模型。

针对要求潜艇声学覆盖层兼具低频宽带吸声性能和耐静压能力的设计难题，本项目综合应用结构优化设计、低频隔振、变换声学、声子晶体和声学超材料等理论，探索了新型水下耐静压、低频宽带超薄吸声结构的设计原理。至今项目已顺利完成，既获得了诸多的理论成果，也设计了多种可推广应用的具有原创性的声学结构。.理论成果包括：①设计了由变截面型腔和在型腔中填充的声学各向异性材料构成的声波汇聚单元，提出了声波汇聚单元的优化设计策略和方法；②设计了与声波汇聚单元相匹配的曲折声波迷宫通道，提出了声波迷宫通道的优化设计策略和方法；③设计了由曲折声波迷宫通道和在通道中布置的多频率点局部振子构成的声波吸收单元，提出了声波吸收单元的优化设计策略和方法；④设计了由柔性机构和近零刚度机构构成的具有自适应调节静载能力的近零刚度支撑，提出了具有自适应调节静载能力的近零刚度支撑的优化设计策略和方法；⑤设计了由声波汇聚单元、声波吸收单元和近零刚度支撑构成的吸声结构，提出了低频宽带超薄吸声结构的优化设计策略和方法。.可推广应用的声学结构由13项授权的国际和中国专利支撑，包括：新型超薄声波阻抗变换器、控制声波传播路径的宽带超薄吸声结构、隔声结构和声波扩散结构，以及低通声滤波器组宽频吸声体。这些声学结构，能应用于航空航天船舶车辆和社会人文等各个领域，有广泛的应用前景。如：有减振降噪要求的飞机轮船车辆的产品设计、有高精度要求的制造装备产品和精密仪器、有静音设计要求的冰箱空调等家电产品、有超薄设计要求的电视手机等电子产品、有减小尺寸要求的大号长号萨克斯等管乐器、具有较高声品质要求的大型会议室、音乐厅和影院等。.基于本项目，课题组培养研究生35人，其中毕业21人；发表论文11篇，全部被EI检索；获得授权专利13项，包括美国1项、欧盟3项、英国3项、德国3项，中国3项。本项目的成果兼具设计原理上的创新，以及结构和技术手段上的奇思妙想，既有科学价值，也具有实用性。