三维绝热简正波-抛物方程理论及应用

摘要

Complex zone of the ocean is often characterized by horizontal variations of environmental parameters (bathymetry, sound speed profile, bottom properties etc.), initiating redistribution of the sound field in horizontal plane, which is the so-called three-dimensional (3D) effect. Based on the adiabatic mode parabolic equation method, modeling of 3D effects is carried out, in which the eigenvalues and eigenfunctions are calculated by the standard normal mode model KRAKEN, and the amplitude corresponding to each mode is computed by the wide-angle parabolic equation model RAM. The present 3D model is very efficient and can give clear physical meaning, but it can be only applied to a waveguide whose properties vary gradually with horizontal range due to the adiabatic assumption between different modes. This model is then used to analyze the horizontal refraction caused by internal waves and by a coastal wedge. The numerical results show that there are several areas in the horizontal plane, corresponding to different structures of intensity distributions. Moreover, the redistribution of the sound field in horizontal plane depends on source frequency and mode number. Frequency and modal dependences lead to variations of spectrum, distortion of signal with some spectrum, and spatiotemporal fluctuations of the sound field.%复杂海域通常存在环境参数的水平变化，这会导致声波在传播过程中发生水平折射，呈现出三维效应。利用绝热简正波-抛物方程理论进行三维声场建模，在垂直方向上使用标准简正波模型KRAKEN求解本征值和本征函数，水平方向上使用宽角抛物方程模型RAM求解简正波幅度。该模型物理意义清晰，计算效率高，但由于忽略了各号简正波之间的耦合，只适用于环境参数水平变化缓慢的问题。使用该模型分析了内波环境和大陆架楔形波导中的声波水平折射现象，结果表明，声波的水平折射将水平平面分为不同区域，每个区域内的声场结构明显不同。此外，声强在水平平面内的分布与声源频率和简正波号数有关，这种依赖关系是导致声信号频谱变化、波形畸变以及声场时空扰动的主要原因。