不规则波在一种复杂断面海堤上越浪的数值模拟研究

以不可压缩黏性流体的Navier-Stokes方程为控制方程,利用VOF方法追踪运动的自由表面,建立了立面二维数值波浪水槽。基于经典溃坝算例验证了数值模型的可靠性,然后采用动边界造波技术生成不规则波浪,对复杂断面海堤上的不规则波越浪进行了模拟和分析,计算结果与实验结果符合。     

孤立波作用下斜坡堤越浪量的实验研究

为了研究海啸等浅水大波对海堤等海岸结构物的作用,采用孤立波作为输入波形,在波浪水槽中进行了孤立波在斜坡堤上越浪过程的系列实验。通过物理模型实验,获得了孤立波作用下斜坡堤越浪量的测量结果,并基于PIV方法测量得到的海堤越浪流速度场计算了越浪量。以堤顶相对超高和来波相对波高为无量纲参数,基于越浪量实验数据建立了斜坡堤上孤立波越浪量的经验预报公式。孤立波堤顶越浪流的PIV测量结果表明,在实验工况条件下越堤流流场可近似为几乎平行的流动;基于PIV测量结果得到孤立波越浪量与越浪量的直接测量结果一致性较好。对简单斜坡堤而言,无量纲的孤立波越浪量随来波相对波高的增大而增加,随着堤顶相对超高的减小呈指数增大。     

带异形块体海堤越浪的数值模拟

该文在FLUENT软件平台上，发展了数值消波-造波技术，通过在动量方程里添加多孔介质源项，建立了带有多孔介质模型的二维数值波浪水槽。应用该数值波浪水槽，数值模拟了在斜坡堤坡面上铺设异形块体情况下的越浪过程，给出了越浪量。为了率定异形块体的等效惯性阻力系数，进行了典型工况的物理模型实验，给出了在斜坡堤坡面上不同位置处铺设一层异形块体情况下多孔介质模型的等效阻力系数。     

海堤遭遇越浪流溃决形式研究

为了研究海堤遭遇越浪流时的破坏形式,在前人研究的基础上,采用水力学和土力学理论研究了海堤溃决的物理力学机制,分析了越浪冲刷过程中海堤的溃决机理,提出了海堤越浪流的"陡坎"溃决模型,模拟了海堤越浪流的"陡坎"溃决过程。通过对遭遇9417、9711号台风时浙江省沿海海堤的实际破坏、溃决情况调查,验证了"陡坎"溃决模型的合理性。     

基于高精度WENO格式的二维溃坝波数值模拟

以浅水波方程组建立二维溃坝洪水模型,对经典WENO格式计算模板重新选取,得到各计算模板上重构多项式,对各个模板的局部光滑因子进行组合得到更高阶的全局光滑因子,建立相应的非线性权,将各模板上重构多项式加权处理得到计算单元界面数值通量的一个新高精度WENO格式,泰勒级数展开证明了该格式的非线性权比经典WENO格式的非线性权更接近理想权。将该格式、Lax-Friedrich通量分裂方法和局部特征分解方法相结合用于二维浅水方程的离散求解,模拟二维局部溃坝流和圆形溃坝流洪水的演进过程,模拟结果与实际流动符合较好,表明采用高精度WENO格式所建立的高分辨率溃坝模型能很好地模拟溃坝波的演进过程。     

滑坡激起侧向冲击浪的模拟研究

正滑坡引起的巨大冲击浪是滑坡灾害的一种严重次生灾害,其侧向冲击浪沿河道向上下游传播,易对沿岸居民及航道船只的安全带来安全隐患。因而,其侧向浪高是评价河道中滑坡冲击浪强度的重要因子之一。模拟滑坡激起的冲击浪的数学模型依据其控制方程的不同,主要分为基于浅水长波方程的模型、基于Boussinesq方程的模型、基于完全非线性势流理论的模型、基于N-S方程的模型等4种主要类型。其     

不平水底浅水波问题的位移法

该文研究考虑不平水底的二维浅水波问题的位移法。利用水平位移与竖向坐标无关的假定,建立了基于位移的浅水波方程和相应的Hamilton变分原理。针对文中提出的基于位移的浅水波方程,利用有限元和保辛算法建立了相应的计算格式。最后给出一个具有抛物线型河床的浅水周期晃荡算例。数值算例表明该方法可以有效模拟带动边界和不平水底浅水波问题。     

潜堤上波浪传播过程数值研究

以RANS方程结合Level-Set方法为研究基础,采用五阶WENO有限差分格式进行空间离散、三阶TVD Runge-Kutta格式进行时间推进、Level-Set方法追踪波浪与空气间自由面以及解析松弛法来实现数值水槽中的造波消波,建立了一种求解潜堤上波浪传播问题的数值计算模型。选取经典的潜堤上波浪传播物理试验模型对数值模型进行了验证,水位计算结果与试验值吻合较好。进一步研究了波高、潜堤顶部淹没深度以及潜堤坡度等参数对潜堤上波浪传播过程的影响。结果表明:波高越高、淹没深度越浅、潜堤向波坡度越小,波浪受浅水作用越明显;潜堤背波坡度越小,波浪受反浅水作用稍大,但并不明显。     

基于全非线性层析水波理论的波群时历模拟研究

为了研究波群作用下的船舶参数激励横摇特性,该文引入了高阶无旋层析水波理论（HLIGN）开展波群的数值模拟研究。结合C11集装箱船顶浪不规则波参数横摇模型试验的测试数据,选取目标波群样本,通过二阶非线性造波理论获得了波群造波水池试验结果。利用全非线性波浪模型对波群进行数值模拟,给出了波群模拟时的造波边界设置和计算参数设置方法,并通过与物理造波结果对比发现,HIGN波浪模型对波群模拟有较高的精度,可很好地模拟波群的非线性传播特性。     

规则波作用下潜堤透浪系数数值模拟

潜堤透浪系数是衡量潜堤削弱波浪能力的主要指标。基于Boussinesq型方程的MIKE21-BW模型建立波浪数值水槽,进行规则波作用下潜堤透浪系数的数值模拟。根据Dingemans物理模型试验结果对BW模型进行参数率定和验证,验证结果良好。在此基础上,进一步分析了影响潜堤透浪系数的无因次影响参数,包含相对淹没深度、波陡、相对堤顶宽度、斜坡堤坡度等,研究不同因素组合情况下潜堤透浪系数的变化规律。建立了规则波作用下潜堤透浪系数的计算式,应用MATLAB数学软件对式中的系数进行拟合,拟合式计算值与BW模型计算值相关系数为0.858,相关性较好。另外,将拟合式与杨正己公式进行比较,并分析数据的差异与原因。研究表明:MIKE21-BW模型可以进行规则波作用下潜堤透浪系数的数值模拟。     

NUMERICAL SIMULATION OF SOLITARY WAVE RUN-UP AND OVER-TOPPING USING BOUSSINESQ-TYPE MODEL

In this article,the use of a high-order Boussinesq-type model and sets of laboratory experiments in a large scale flume of breaking solitary waves climbing up slopes with two inclinations are presented to study the shoreline behavior of breaking and non-breaking solitary waves on plane slopes.The scale effect on run-up height is briefly discussed.The model simulation capability is well validated against the available laboratory data and present experiments.Then,serial numerical tests are conducted to study the shoreline motion correlated with the effects of beach slope and wave nonlinearity for breaking and non-breaking waves.The empirical formula proposed by Hsiao et al.for predicting the maximum run-up height of a breaking solitary wave on plane slopes with a wide range of slope inclinations is confirmed to be cautious.Furthermore,solitary waves impacting and overtopping an impermeable sloping seawall at various water depths are investigated.Laboratory data of run-up height,shoreline motion,free surface elevation and overtopping discharge are presented.Comparisons of run-up,run-down,shoreline trajectory and wave overtopping discharge are made.A fairly good agreement is seen between numerical results and experimental data.It elucidates that the present depth-integrated model can be used as an efficient tool for predicting a wide spectrum of coastal problems.     

孤立波翻越防波堤流动的湍流数值模拟

应用湍流数学模型和流体体积法模拟孤立波翻越防波堤的流动和自由表面变化。数模成功地再现了波浪涌顶和喷射、射流入水、自由表面破碎和漩涡产生等复杂流动过程,并获得了孤立波翻越防波堤时的压力分布。     

土石坝漫顶过程水力特性分析

土石坝漫顶过程极其复杂,溃决过程研究成果存在诸多争议。采用标准k~ε紊流模型和VOF方法对土石坝水流漫顶过程进行了水气两相流数值模拟,对漫顶过程水流流态、流速分布等进行了详细分析,揭示了坝面切应力分布规律。该规律的发现可以用于解释笔者先前提出的"落点冲蚀"猜想及"剪剥式"冲蚀理论,即漫顶条件下最先发生冲蚀的部位可能在坝坡中上部,漫顶冲蚀以台阶式冲蚀为溃决的主要特征。     

NUMERICAL SIMULATIONS OF NONLINEAR WAVES OVERTOPPING AN OBSTRUCTION

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数值模拟波浪翻越直立方柱

本文应用ＶＯＦ方法研究了孤立波翻越直立方柱流动的全过程。用人工压缩法和差分法求解二维Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程，用施主－受主法求解流体体积函数控制方程。通过数值计算得到了孤立波翻越直立方柱的流场和压力值，并成功地模拟出波浪涌顶，水柱喷射，冲击和界面破碎的过程。     

NUMERICAL SIMULATION OF TWO-DIMENSIONAL OVERTOPPING AGAINST SEAWALLS ARMORED WITH ARTIFICIAL UNITS IN REGULAR WAVES

A new mathematical model for the overtopping against seawalls armored with artificial units in regular waves was established. The 2-D numerical wave flume, based on the Reynolds Averaged Navier-Stokes (RANS) equations and the standard k-ε turbulence model, was developed to simulate the turbulent flows with the free surface, in which the Volume Of Fluid (VOF) method was used to handle the large deformation of the free surface and the relaxation approach of combined wave generation and absorbing was implemented. In order to consider the effects of energy dissipation due to the armors on a slope seawall, a porous media model was proposed and implemented in the numerical wave flume. A series of physical model experiments were carried out in the same condition of the numerical simulation to determine the drag coefficient in the porous media model in terms of the overtopping discharge. Compared the computational value of overtopping over the seawall with the experimental data, the values of the effective drag coefficient was calibrated for the layers of blocks at different locations along the seawalls.     

THE VOF METHOD FOR STUDY OF WAVE RUN-UP AND BREAKING ON A SLOPING STRUCTURE

The volume of fluid method(VOF method)for numerical simulations describing wave run-up on a sloping structure including the overturning,breaking and.merging phenomena is presented.The flow motions are governed by the classical,two-dimen-sional Navier-Stokes equation for incompressible fluid.Computational results concerning the time evolution of the free surface and pressure distribution along water bed and slope boundary are given,showing how an initial solitary wave undergoes run-up,overturning,breaking and merging on the slope.It is found that most of the wave energy is lost after the wave breaking and merging.     

考虑振幅弥散影响的波浪变形模型

本文给出了一个精度高于Zhao和Anastasiou（1993）显式近似Kirby和Dalrym-ple的非线性经验弥散关系的显式表达式，该显式表达式与Kirby和Dalrym-ple的非线性经验弥散关系吻合很好。用本文给出的非线性弥散关系显式表达式，结合含弱线性经效应的缓坡方程的前进波折近似方程组，建立了一个考虑振幅弥散影响的波浪变形模型，用文中模型对波浪的变形进行了计算，将计算结果和试验数据（试验数据采用Berkhoff等（1982）验证数学模型可信性试验进行了比较。结果表明，采用本文的波浪变形模型，所得计算结果与试验结果更为吻合。     

单坡堤上不规则波越浪量的估算

通过对影响单坡堤上不规则波越浪量的主要物理因素的分析，根据模型试验结果，讨论了各相关因子对越浪量的影响，从而可由波浪特征值及建筑物形态来确定越堤水量。     

APPLICATION OF A NOVEL ALGORITHM FOR MOVING SURFACE FLOWS

Purpose:To demonstrate a novel algorithm for simulating moving surface flows. Methods: A fully conservative control volume method, on an adaptive Eulerian grid, has been developed to guarantee that the "kinematic free surface condition "is automatically satisfied by solving the mass and momentum conservation equations. No separate free surface tracing equation is needed. The basic idea has been extended to solve general moving surface problems by adding "boundary-node-constraints" to the solution equation set. Results; Two application problems, a critical free surface flow over an obstruction and flow past a 2-D inflated building, were predicted by the proposed method. The predicted results were in good agreement with the corresponding experimental findings. Conclusions: The proposed moving surface model permits prescribed moving walls, free surfaces, and compliant surfaces to be simulated by the same computer code. The moving surface shape is obtained as part of the solution of the conservation equation