利用单模发射的浅海内波环境下声场简正波耦合效应研究

Internal waves (Internal tide and nonlinear internal waves) are common in shallow water of continental shelves and adjacent seas, cause strong acoustic normal mode coupling and lead to rapidly normal mode amplitudes, traveling time, temporal and cross-range coherence fluctuation. Normal mode coupling usually is shown by coupling matrix. Coupling matrix is the important physical quantities, which shows internal waves affect on acoustic field. The rules of sound energy transferring between different normal modes and sound fluctuations may be understood with coupling matrix. Usually, it is hard to get accurate, complete coupling matrix, so research on the relation between coupling matrix and internal wave's characteristic is based on numerical simulation. Many of results lack the support of experimental dada, which restricts the progress of sound fluctuation. Single normal mode excitation technique provides an effective means to get mode coupling matrix in shallow water internal waves. In project, experimental method of single mode acoustic field excitation would be used to get the coupling matrix. Results of literature would be test using coupling matrix data. Conditions and rules of normal mode coupling would be built. Succeed of the project will has important scientific significance for research on internal waves affect on acoustic fluctuation and internal waves inversion.

夏季的浅海海域，潮汐内波和非线性内波活动频繁, 引起声传播的能量在不同号简正波之间进行转移的耦合现象,导致了接收声场的幅度、传播时间、时空相关性等出现快速的变化。简正波耦合现象主要通过耦合矩阵的形式来给出，耦合矩阵是反映内波对声场影响的重要物理量。通常情况下，要得到比较准确、完整的耦合矩阵是非常困难的。对耦合效应与内波特征的关联性研究大多建立在数值分析上，许多结果缺乏实验数据的支持和检验，制约了内波引起声场起伏研究的进步。单模（单号简正波）发射技术的出现为内波环境下的耦合矩阵获取提供了一种有效的手段。本项目拟采用理论建模结合单模声场激发的实验手段，来获得不同内波环境下不同频率声场的简正波耦合矩阵，从耦合矩阵的分析入手，对已有的一些的结论进行验证，并总结和完善内波环境下简正波相互耦合的条件和规律。该项目的成功开展对内波引起声场起伏的规律研究以及内波的声学反演方法研究都有比较重要的科学意义。

内波对声场影响研究是水声学的研究热点之一，内波活动引起声传播的能量在不同号简正波之间进行转移的耦合现象,导致了接收声场的幅度、传播时间、时空相关性等出现快速的变化。简正波耦合现象主要通过耦合矩阵的形式来给出，耦合矩阵是反映内波对声场影响的重要物理量。项目组利用声源激发单号简正波(单模)声场的方式给出了提取内潮和非线性内波环境下简正波耦合矩阵的方法；讨论了内波引起各号简正波耦合的量化关系；利用23元相控发射阵进行了内波环境下单模声场耦合效应获取的海上试验，在试验中测量了黄海内波环境下单号简正波通过内波后的接收声场数据，实现了利用单模声场来获取内波环境下声场简正波耦合矩阵。测量数据表明，黄海内波引起619Hz声场第3号简正波的能量向1号和2号简正波耦合。项目研究成果和相关数据对促进内波对声场影响的规律研究有一定的科学意义。