浅海矢量声场干涉结构形成机理及试验研究

浅海低频声场的微观结构特征在于具有可用波导不变量表征的 稳定空间-频率干涉结构.声场兼具标量场和矢量场, 波导条件下二者联合决定声场的全部特性. 本文研究浅海声场空频干涉结构的矢量场特征. 理论分析了声压谱、动能密度谱、声强流谱等矢量场干涉结构的形成机理, 探讨了矢量场干涉结构的波导不变量表征, 数值仿真研究了Pekeris波导中能量和能流密度的干涉特性, 进行了宽带声源辐射矢量声场干涉特性及表征的海上试验.实测结果与理论、仿真分析有较好的一致性. 研究结果表明: 中近程和中远程声场均能模态相干, 有稳定的空频干涉结构, 并且矢量声场空频干涉结构存在多种形式, 除各种能量和能流密度谱图外, 相干系数谱也呈现干涉特征, 这些形式的空频干涉结构均可用波导不变量理论有效表征. 关键词： 矢量声场 干涉结构 波导不变量 浅海低频声场

The mechanism of the interference structure in shallow water vector acoustic field and experimental investigation

The microscopic structure characteristic of low frequency sound propagation in shallow water is that a stable space-frequency interference structure represented by waveguide invariant exists. Both the scalar field and the vector field determine all the features of the acoustic field. The vector field characteristics of space-frequency interference structure in shallow water acoustic field are investigated. The theoretical analyses of the mechanism of interference structure in the sound pressure spectrum, the kinetic energy density spectrum, and the acoustic intensity flow spectrum in shallow water vector acoustic field are conducted, the numerical simulation studies of the interference of the Pekeris waveguide in energy and energy flow density characteristics are performed, and the sea trials for broadband sound source radiation vector sound field interference properties and characterization are also carried out. The experimental results accord with the theoretical analyses and simulation results very well. The research results show that stable space-frequency interference structure in acoustic vector field exists in many forms for modal coherent in short-distance and long-distance. In addition to various forms of energy and energy flux density spectra, in coherence-coefficient spectrum there appear the interference characteristics. These forms of space-frequency interference structure can be described by waveguide invariant theory effectively.
Keywords： vector acoustic field interference structure waveguide invariant low frequency acoustic field in shallow water