粗糙海面散射引起的浅海远程混响特性起伏及机理研究

The impact of ocean reverberation on the performance of active sonar system is hardly avoided, and it had always been a hot issue of underwater acoustics. Both the experimental data and theoretical research had shown that time and space variant ocean environmental parameters would cause large prediction uncertainties of reverberation. For example, reverberation prediction uncertainty that introduced only by sea surface scattering can be remarkable enough, of order 5 dB at 8km. Most of current reverberation model are still based on the empirical scattering kernel, and it’s really hard to get the physical mechanism of rough surface scattering. Therefore, more and more researchers have been focus on how sea surface scattering affect reverberation prediction uncertainties. The scientific issue of this project pay close attention to the influence of rough sea surface scattering on long range reverberation in shallow water. The scattered field will be considered as the interaction of the incident modes with rough surfaces, and the complex propagation effect of the waveguide with rough sea surface will be investigated and quantified. This research is at forefront of the reverberation research in worldwide, and can provide a physical foundation for development of new long range detection system.

海洋混响是主动声纳系统不可回避的重要干扰，也是水声学研究的热点与难点。浅海远程混响受海洋波导效应影响显著。实测数据和最新研究结果均表明：海洋波导环境的时变空变特性可导致混响特性预报有很强的不确定性。例如：海面散射效应可导致8km处混响强度预报值产生约5dB的起伏，这将严重制约水声设备的性能和海洋环境信息获取的精度。目前的混响理论模型多采用经验散射函数，缺乏对起伏海面散射过程的物理分析。近年来国际上尤其重视研究海面散射对浅海混响预报不确定性的影响与物理机制。本课题围绕“起伏海面散射对浅海远程混响的影响机理”这一科学问题，深入研究起伏海面散射对远程混响强度特性、空间相关特性的影响和物理过程。从粗糙海面散射如何影响声场模态间能量转换的角度，研究海面起伏对海底混响的影响机理。这不但符合最新的国际学术发展潮流，而且对我国低频主动探测新原理、新方法的发展具有重要研究价值和国防意义。

本项目针对浅海中起伏海面散射引起的混响问题，从粗糙海面与声波的相互耦合角度，利用耦合简正波理论表述了粗糙界面散射对声场的再辐射过程。其优势是便于对界面散射的物理过程进行机理性探讨和分析。重点通过对起伏海面散射引起的模态间能量耦合的分析，对起伏海面效应引起的海底混响强度及空间相关特性的变化特点进行了机理性探讨。结果表明：起伏海面改变了浅海波导的传输特性，海况越差，海面散射引起的模态间能量耦合就会越剧烈，最终表现为增加声场的海面反射损失，使高阶模态更快的消逝掉，因此远程海底混响强度会变小，空间相关特性则会增强。这不但符合该领域最新的国际学术发展潮流，而且对我国海洋声学设备、水声装备的新型混响抑制方法的提出有实际研究价值。