稳定层化海洋中潜航体自航湍流尾迹及其海表特征数值方法研究

With the developments of the non-acoustic detection technologies, submarine non-acoustic stealth performances are facing great threats. The density of the ocean is usually stably stratified in vertical direction because of varieties of the temperature and salinity of the seawater. When a submerged body with propeller navigating under the ocean, it can generate turbulent wakes with sea surface features which will become important targets of non-acoustic detections. Meticulous numerical simulations of the submerged body turbulent wakes should be implemented in order to make clear of the space and time structures and also the sea surface characteristics of the wakes. This project is based on the basic principles of the computational fluid dynamics (CFD) and uses the thermal density current model to realize the density stratification of the of fluid. The overlapping grid (Overset) technologies will be implemented to attaining the submerged body movements and propeller operations. The numerical simulations of turbulence in the wake will adopt the detached eddy simulation(DES) methods. Analysis of the DES methods will focus on the high efficiency and reliability for capturing the details in the core area of the turbulent wakes. One of the important purposes of this project is to seeking the theoretical models and prediction methods of turbulent wakes behind a submerged body, especially for the methods to capture the fine unsteady phenomenon of the wakes. And also it will carry out the comparative analysis of the time and space structural evolutions of the submerged body turbulent wakes. On this basis, this project intend to using the CLSVOF method to capture the free surface features of the turbulent wakes. CLSVOF is a coupled method of VOF and Level-Set method, which can improve the capability of the free surface tracking. The researches of this project will have important theoretical significances for the numerical simulations of the stratified environments of the ocean and also have important application values for the developments and progress of the submarine non-acoustic detection technologies.

随着非声探测技术的发展，潜航体（如潜艇）非声隐身性能面临极大威胁。在密度稳定分层海洋中，潜航体自航产生的湍流尾迹及其海表特征会成为非声探测的重要目标。为明确潜航体湍流尾迹时空结构及海表特征，需建立潜航体湍流尾迹的精细数值模拟方法。本项目基于计算流体力学基本原理，采用温度异重流模型实现流体密度分层；拟采用重叠网格（Overset）技术，实现潜航体运动及螺旋桨运转；研究探索脱体涡（DES）方法在湍流尾迹数值模拟中的具体实现，着重探讨湍流尾迹核心区的模拟方法，以期能够精细捕捉湍流尾迹中的非定常现象，最终寻求构建潜航体湍流尾迹计算预报理论方法，并开展潜航体湍流尾迹时空结构和演化规律分析。在此基础上，拟采用耦合的CLSVOF方法，建立追踪湍流尾迹自由表面特征的方法。本项目的研究工作对发展稳定分层海洋中潜航体水动力尾迹的数值模拟具有重要理论意义，对潜艇非声探测技术的发展和进步具有重要应用价值。

由于温度、盐度等外部因素变化的影响，海洋水体通常会呈现出密度稳定分层的特性，当潜航体在分层海洋内部以一定的航速航行时，潜航体与周围水体相互作用，会产生丰富的水动力尾迹特征。潜航体水动力尾迹具有显著的非定常流动特性，对潜航体的水下隐蔽性和水下航渡构成了严重威胁。该项目即针对潜航体水下带桨自航时产生的分层湍流尾迹，围绕湍流尾迹的数值模拟方法以及自航运动的实现方法，对湍流尾迹产生机理、时空演化结构等方面展开研究，探索对湍流尾迹产生的海表特征进行精细捕捉和追踪的方法，为潜航体带桨自航湍流尾迹特征的进一步研究奠定基础。该项目通过调研相关密度分层、温度分层和盐度分层水文资料，基于温度异重流模型构建相关海洋水体稳定密度分层物理模型，探索其变化规律。研究分析基于船舶精细计算流体动力学方法（CFD）及高精度湍流数值模拟方法（LES\DES）等，提出并构建了一套稳定海洋分层环境数学模型及潜航体分层尾流流动及湍流尾迹海表特征的数值模拟方法。对提出的密度分层湍流流动数值模拟方法进行了数值验证工作，同时开展了实现潜航体自航的重叠网格和滑移网格技术研究，并开展典型潜航体的内波尾迹和湍流尾迹数值模拟工作。拓展研究了潜航体热排放尾迹和冷尾迹的海表温度变化特征及其演化规律。采用重叠网格技术和滑移网格技术，模拟真实螺旋桨转动过程，利用PI控制思想实现自航点寻找，进而实现潜航体的定速直航自航运动，总结分析了采用VOF 及相关拓展方法进行潜航体尾迹自由表面追踪的方法。在以上研究工作基础上，着重开展了潜航体湍流尾迹海表特征研究工作，对Suboff潜体定速直航时的湍流尾迹静水面自由表面特征进行定性定量研究，并拓展分析了尾迹海表特征的雷达散射成像仿真研究，研究了潜航体加减速机动过程、附体及其安装形式等对潜航体分层尾迹的影响规律。该项目的研究工作可用于评估潜航体尾迹隐蔽性，并针对隐蔽性需求提供改善措施和控制原则。