复杂条件下潜艇推进器流噪声高效数值预报研究

Numerical prediction on the flow noise from submarine propeller is one of the key techniques in developing quiet submarine. Most of the previous study on the issue is carried out by assuming the following conditions: the blade of the propeller is rigid, the submarine is maneuvered with constant velocity and the sound speed in the ocean is also constant. The following complex conditions are rarely involved, although they are closer to the real circumstance. They are: the blade of the propeller is flexible, the submarine is maneuvered with acceleration and the sound speed in the ocean is at least spatial variable. In this project, the numerical simulation method based on the lattice Boltzmann (LB) method is used to investigate the generation and propagation of flow noise from submarine propeller under such circumstance. The following issues are mainly included: propose proper numerical models and tools for implementation of the boundaries conditions based on LB method which can accurately describe the influence of the complex conditions on the flow noise; develop an efficient numerical platform of the flow noise prediction on the GPU-CPU heterogeneous computer systems; Investigate the influence of the complex conditions on the far field intensity distribution, the directivity, frequency pattern of the flow noise using this platform and analyze the contributions of different noise sources (monopole ,dipole and quadrupole) on the total noise. With this project, we hope we can provide an efficient reasonable method for numerical prediction of underwater flow noise under such complex conditions, and then a theoretical guidance for corresponding noise reduction methods.

潜艇推进器流噪声数值预报是开发安静型潜艇的关键技术之一。目前关于潜艇推进器流噪声数值预报的研究多是假定推进器叶片为刚体、潜艇均速机动和空间声速为常数的条件，很少涉及叶片结构形变、潜艇变速机动及声速空间变化等更接近真实的复杂条件。鉴于此，本项目拟采用基于格子Boltzmann（LB）方法的数值模拟手段，对此类条件下潜艇推进器流噪声的产生传播机理进行研究。主要包括：构建能准确刻画此类条件影响的LB模型及边界处理格式，开发能实现上述LB模型的GPU-CPU异构计算机系统条件下的流噪声高效数值预报平台，并借此平台探究叶片结构形变、潜艇变速机动及声速空间变化对潜艇推进器流噪声远场声源强度分布、辐射方向、频率特性等的影响规律，分析这种条件下不同噪声源(单极子、偶极子和四极子等)对总体噪声的贡献。本项目研究可望为认识此类条件下水下流噪声产生传播机理提供合理高效的方法，为相应消声降噪技术提供理论支持。

潜艇推进器流噪声数值预报是开发安静型潜艇的关键技术之一。本项目针对目前潜艇推进器流噪声数值预报的研究很少涉及叶片结构形变、潜艇变速机动及声速空间变化等这类更接近真实条件下的流噪声建模仿真与物理机理取得如下主要研究成果：（1）基于格子Boltzmann方法的数值框架，构建了一系列能准确刻画此类条件影响的 LB 模型及边界处理格式。提出了基于力修正的LB-IBM新方法克服已有模型的数值滑移问题，耦合了计算稳定性较好的光滑粒子方法处理固体大变形问题。发展了基于Buick模型的LB方法处理声速空间变化的问题。（2）基于这些格式，初步建立了一套自主知识产权的能够刻画上述条件影响的流噪声高效数值预报平台。数值仿真和实验表明了方法的高性能。（3）借此平台研究了上述复杂条件下的流噪声譬如可变形旋转椭圆柱流噪声产生和传播规律，得到了符合物理实际的结果。上述研究结果进一步证实了基于LB方法的流噪声数值建模方法的优越性，为潜艇复杂条件下的消声降噪技术提供了可靠的数值预报工具。