非线性波浪波面追踪的一种新模式

基于Laplace方程的Green积分表达式和波面BemouUi方程所建立的非线性波动数学模型,是一个时域上具有初始值的边值问题,而精确地追踪自由表面的波动位置,给出波面运动瞬时的波面高度和波面势函数,是建立时域内非线性波浪数值模式的基础。本文采用0-1混合型边界元剖分计算域边界并离散Laplace方程的Green积分表达式,采用有限元剖分自由水面并推导满足自由表面非线性边界条件的波面有限元方程,联立计算域内以节点波势函数和波面位置高度的时间增量为未知量的线性方程组,通过时步内的循环迭代,给出每个时步上的波面位置和波面势函数,从而建立了一种新的非线性波浪波面追踪模式。数值造波水槽内的波浪试验表明,其数值模拟结果具有良好的计算精度。     

海洋-声学-探测模型的并行预报技术研究

针对声纳探测性能预报的需求,建立了海洋-声学-探测模型,实现了并行计算。该模型将海洋数值预报模式、声学模式与海洋观测资源进行整合,辅以战术需求,实现了对水声环境和声纳探测性能的动态预报和估计。同时,结合高性能计算机系统,设计并实现了模型的并行算法,结果表明,该程序具有较高的并行性能,较好地满足了声纳探测性能预报对实效性的要求,为形成业务化海洋水声环境预报能力打下了良好的基础。     

人工神经网络在潮汐数值预报中的应用

潮汐数值预报经过了几十年的发展,但是其预报精度并不能让人十分满意,本文试图将传统的潮汐数值预报模式与近年来发展迅速的人工神经网络相结合并改进潮汐数值预报的精度。文章建立了一个神经网络系统,采用潮汐数值模式的输出结果作为网络输入,潮位观测资料作为输出,用建立的神经网络进行训练,结果表明人工神经网络可以明显地改进潮汐数值预报的精度。     

蓬莱19-3 油田事故溢油数值模拟

利用FVCOM(Finite-volume coastal ocean numerical model)数值模型和MM5风场预报模式,在对渤海海域水动力场进行数值模拟的基础上,基于"油粒子"的欧拉-拉格朗日跟踪法和随机走动原理,并考虑风对溢油油膜漂移扩散的直接作用,建立了海洋溢油油膜漂移轨迹和扩散的数值预测模型。利用建立的模型对2011年6月蓬莱19-3油田事故溢油进行了数值模拟,模拟结果与RADARSAT卫星遥感监测数据相吻合。研究结果表明:在渤海中部地区夏季事故溢油模拟预测中,风漂移因子取0.024最为合理,模型可用于渤海蓬莱19-3油田附近事故溢油轨迹和扩散的快速预报,从而为该区域的溢油事故应急响应提供科学依据。     

高分辨率浪-潮-流耦合数值预报系统的业务化运行与检验分析

依据我国独立发展的浪致混合理论,基于MASNUM第三代海浪数值模式和三维POM海流数值模式,研制开发了高分辨率浪-潮-流耦合数值预报系统并进行了(准)业务化运行与预报产品精度检验.该浪-潮-流耦合数值预报系统能够提供全球、西北太平洋和中国近海三个海域不同分辨率的海浪、海流以及温度、盐度等数值预报产品.基于卫星遥感数据、...     

偏心荷载作用下条形浅基础荷载-变形特性数值分析

在主应力方向的旋转过程中,主应力方向与塑性主应变增量方向之间存在着非共轴现象。基于屈服角点结构非共轴理论,建立了一种非共轴本构模型,通过有限元软件ABAQUS的二次开发子程序UMAT,将该模型运用到有限元数值计算中。首先,对中密砂单剪试验进行数值模拟,研究了非共轴现象及其对应力-应变关系的影响。然后,针对偏心荷载作用下条形浅基础荷载-变形特性进行数值分析,研究了非共轴现象对荷载-位移关系的影响。研究结果表明:非共轴模型计算得到的荷载增长速度滞后于共轴模型计算结果的增长速度;在地基变形的初期,非共轴现象比较明显,主应力方向的减小速度要滞后于塑性主应变增量方向的减小速度;随着地基沉降的增加,非共轴现象逐渐减弱;非共轴模型与共轴模型计算结果之间的差异在应变硬化情况下更加明显。     

南海及邻近海域大气-海浪-海洋耦合精细化数值预报系统研制

本文主要介绍了南海及邻近海域大气-海浪-海洋耦合精细化数值预报系统的研制概况。预报区域为99°E~135°E，15°S~45°N，包括渤海、黄海、东海和南海及其周边海域。为了给耦合预报模式提供较准确的预报初始场，在预报开始之前，分别进行了海浪模式和海洋模式的前24小时同化后报模拟。海浪模式和海洋模式都采用了集合调整Kalman滤波同化方法，海浪模式同化了Jason-2有效波高数据；海洋模式同化了SST数据、MADT数据和ARGO剖面数据。为了改进海洋温度和盐度的模拟，我们在海洋模式的垂向混合方案中引入波致混合和内波致混合的作用。预报系统的运行主要包括两个阶段，首先海浪模式和海洋模式进行了2014年1月至2015年10月底的同化后报模拟，强迫场源自欧洲气象中心的六小时的再分析数据产品。然后耦合预报系统将同化后报模拟的结果作为初始场进行了14个月的耦合预报。预报产品包括大气产品（气温、风速风向、气压等）、海浪产品（有效波高和波向等）、海流产品（温度、盐度和海流等）。一系列观测资料的检验比较表明该大气-海浪-海洋耦合精细化数值预报系统的预报结果较为可靠，可以为南海及周边海洋资源开发和安全保障提供数据和信息产品服务。     

北印度洋风浪流数值预报系统:Ⅰ-设计与实现

以5°S以北印度洋海域为目标区域,基于区域大气模式WRF、海浪模式SWAN和海流模式ROMS,建立了北印度洋风浪流数值预报系统。该系统具有运行稳定、针对性强和产品定制灵活等特点,为海洋环境预报、舰艇航行保障、军事行动准备等提供准确及时的常规和定制风浪流数值预报产品。     

串联浮筒多组分锚泊线松弛-张紧特性分析

为研究松弛-张紧现象对串联浮筒多组分锚泊线的影响以及规律,本文对其松弛-张紧特性进行了数值模拟分析。基于向量式有限元(VFIFE)方法,建立了以锚链-锚缆-锚链多段锚泊线和浮筒组合而成的多组分锚泊线动力学分析模型,研究了串联浮筒多组分锚泊线的松弛-张紧特性。在顶端水平预张力为定值的条件下,通过改变顶端纵荡激励的振幅和频率以及浮筒的浮重、位置和数量,预测串联浮筒多组分锚泊线的松弛-张紧现象发生的条件以及规律。结果表明,通过控制顶端激励的频率和振幅以及浮筒的浮重、位置和数量,可以有效降低松弛-张紧现象的发生,降低串联浮筒多组分锚泊线断裂的风险。     

大气-海浪耦合模式对台风“碧利斯”的数值模拟

本文将海表粗糙度作为耦合大气、海浪模式的重要因子,实现中尺度大气模式MM5(V3)和第三代海浪模式WAVEWATCHⅢ的双向耦合,建立充分考虑大气、海浪相互作用的大气.海浪耦合模式.将该大气-海浪耦合模式应用于对0604次台风"碧利斯"的数值模拟,在耦合模式中引入Smith92海表粗糙度参数化方案,探讨其对台风和台风浪的影响.研究结果表明,大气-海浪耦合模式能够抓住台风过程的总体特征.Smith92海表粗糙度参数化方案对台风路径影响不大.但在台风系统强度的模拟上影响明显,采用Smith92方案使得台风系统强度显著增强,对台风系统强度的模拟有明显改善.同样,大气-海浪耦合模式能够很好的模拟台风过程中海浪的传播和演变.采用Smith92方案使得海面有效波高明显增高,对海面有效波高的模拟有一定程度改善.因此,在大气-海浪耦合模式中恰当的选择海表粗糙度参数化对改进大气-海浪耦合模式的模拟效果是很有意义的.     

Wave Refraction-Diffraction in the Presence of a Current

-Wave refraction-diffraction due to a large ocean structure and topography in the presence of a 'current are studied numerically. The mathematical model is the mild-slope equation developed by Kirby (1984). This equation is solved using a finite and boundary element method. The physical domain is devid-ed into two regions: a slowly varying topography region and a constant water depth region. For waves propagating in the constant water depth region, without current interfering, the mild- slope equation is then reduced to the Helmholtz equation which is solved by boundary element method. In varying topography region, this equation will be solved by finite element method. Conservation of mass and energy flux of the fluid between these two regions is required for composition of these two numerical methods. The numerical scheme proposed here is capable of dealing with water wave problems of different water depths with the main characters of these two methods.     

波浪沿斜面传播过程的数值模拟

精确模拟非线性波沿斜面传播过程非常困难,为此论文从势函数的边界积分方程出发,建立了一种时域内二维波浪模拟的数值模型,主要用来模拟完全非线性波浪的传播变形过程。论文的数值模型使用高阶二维边界元方法,采用可调节时间步长的基于二阶显式泰勒展开的混合欧拉-拉格郎日时间步进来求解带自由表面的线性或完全非线性波浪传播问题。在计算区域一端造出线性或非线性的周期性波浪,另一端采用消除反射波的人工粘性吸收边界。通过与现有理论比较证明了论文数值方法所得结果是准确可靠的。     

Numerical Simulation of Wave Forces on Seabed Pipelines

A three-step finite element method(FEM)together with Large Eddy Simulation(LES)is ap-plied to incompressible turbulent flow around seabed pipelines at relatively high Reynolds numbers.Bothtwo-dimensional and three-dimensional numerical simulation is carried out to determine thethree-dimensional effect.The results of numerical simulation agree quite well with the wave forces actingon pipeline models measured in physical model test.     

A Finite Element Solution of Wave Forces on Submerged Horizontal Circular Cylinders

In this paper, a numerical model is established for estimating the wave forces on a submerged horizontal circular cylinder. For predicting the wave motion, a set of two-dimensional Navier-Stokes equations is solved numerically with a finite element method. In order to track the moving non-linear wave surface boundary, the Navier-Stokes equations are discretized in a moving mesh system. After each computational time step, the mesh is modified according to the changed wave surface boundary. In order to stabilize the numerical procedure, a three-step finite element method is applied in the time integration. The water sloshing in a tank and wave propagation over a submerged bar are simulated for the first time to validate the present model. The computational results agree well with the analytical solution and the experimental data.Finally, the model is applied to the simulation of interaction between waves and a submerged horizontal circular cylinder.The effects of the KC number and the cylinder depth on the wave forces are studied.     

A composite numerical model for wave diffraction in a harbor with varying water depth

A composite numerical model is presented for computing the wave field in a harbor. The mild slope equation is discretized by a finite element method in the domain concerned. Out of the computational domain, the water depth is assumed to be constant. The boundary element method is applied to the outer boundary for dealing with the infinite boundary condition. Because the model satisfies strictly the infinite boundary condition, more accurate results can be obtained. The model is firstly applied to compute the wave diffraction in a narrow rectangular bay and the wave diffraction from a porous cylinder. The numerical results are compared with the analytical solution, experimental data and other numerical results. Good agreements are obtained. Then the model is applied to computing the wave diffraction in a square harbor with varying water depth. The effects of the water depth in the harbor and the incoming wave direction on the wave height distribution are discussed.     

A composite numerical model for wave diffraction in a harbor with varying water depth

A composite numerical model is presented for computing the wave field in a harbor. The mild slope equation is discretized by a finite element method in the domain concerned. Out of the computational domain, the water depth is assumed to be constant. The boundary element method is applied to the outer boundary for dealing with the infinite boundary condition. Because the model satisfies strictly the infinite boundary condition, more accurate results can be obtained. The model is firstly applied to compute the wave diffraction in a narrow rectangular bay and the wave diffraction from a porous cylinder. The numerical results are compared with the analytical solution, experimental data and other numerical results. Good agreements are obtained. Then the model is applied to computing the wave diffraction in a square harbor with varying water depth. The effects of the water depth in the harbor and the incoming wave direction on the wave height distribution are discussed.     

An Improved Coupling of Numerical and Physical Models for Simulating Wave Propagation

An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model (FEM) based Boussinesq equations is applied for the numerical wave simulation, and a 2D piston-type wavemaker is used for the physical wave generation. An innovative scheme combining fourth-order Lagrange interpolation and Runge-Kutta scheme is described for solving the coupling equation. A Transfer function modulation method is presented to minimize the errors induced from the hydrodynamic invalidity of the coupling model and/or the mechanical capability of the wavemaker in area where nonlinearities or dispersion predominate. The overall performance and applicability of the coupling model has been experimentally validated by accounting for both regular and irregular waves and varying bathymetry. Experimental results show that the proposed numerical scheme and transfer function modulation method are efficient for the data transfer from the numerical model to the physical model up to a deterministic level.     

四阶波动方程的有限体积元法

建立一类四阶色散耗散方程全离散有限体积元格式,并给出格式的收敛性和误差估计,同时还给出数值结果。     

Numerical Simulation of Spatial Lag Between Wave Breaking Point and Location of Maximum Wave-Induced Current

A quasi three-dimensional numerical model of wave-driven coastal currents with the effects of surface rollers is developed for the study of the spatial lag between the location of the maximum wave-induced current and the wave breaking point.The governing equations are derived from Navier-Stokes equations and solved by the hybrid method combining the fractional step finite different method in the horizontal plane with a Galerkin finite element method in the vertical direction.The surface rollers effects are considered through incorporating the creation and evolution of the roller area into the free surface shear stress.An energy equation facilitates the computation process which transfers the wave breaking energy dissipation to the surface roller energy.The wave driver model is a phase-averaged wave model based on the wave action balance equation.Two sets of laboratory experiments producing breaking waves that generated longshore currents on a planar beach are used to evaluate the model's performance.The present wave-driven coastal current model with the roller effect in the surface shear stress term can produce satisfactory results by increasing the wave-induced nearshore current velocity inside the surf zone and shifting the location of the maximum longshore current velocity landward.     

应用比例边界有限元法求解多种二维浮体水动力特性

比例边界有限元法(SBFEM)是一种半解析的数值方法,比完全数值方法具有更高的精度,该方法结合了有限元和边界元的优点,采用相对少的剖分单元就可以得到较高精度的模拟结果。通过改变有限子域内部比例中心的位置,使这种方法可以应用到多种形式浮体在波浪作用下的水动力特性的计算中。同时还给出了各种形式浮体的波浪力及反射、透射系数的数值结果,并与边界元方法(BEM)计算结果和特征函数展开方法得到解析解进行了比较,均吻合良好。研究表明比例边界有限元不仅可以计算矩形的浮体结构,而且对于多种结构形式的浮体都可以计算,这为多种结构形式浮体的水动力分析提供了一个可行的方法。