随机波浪中畸形波的数值模拟

文中采用四阶非线性薛定谔方程模拟了二维JONSWAP谱情况下畸形波的生成。分析了深水畸形波的演化过程。探讨了JONSWAP谱参数对峰度和畸形波生成概率的影响。结果表明Benjamin-Feir指数（BFI）是判断波列不稳定调制是否发生的重要参数;峰度值的空间演化曲线和畸形波生成概率曲线趋势一致,峰度值可以预测畸形波生成概率的大小。在随机波浪场中,谱宽较窄和有效波高较小时,畸形波较容易发生。     

非线性聚焦生成畸形波规律之研究

非线性聚焦是畸形波生成的一种可能机理。采用可以描述非线性聚焦现象的四阶修正非线性薛定谔方程,模拟了边带扰动条件下波列空间演化过程中畸形波的生成。不同初始边带扰动条件和不同波陡等情况下的数值试验结果表明,满足边带不稳定性条件时,初始边带扰动条件和波陡对畸形波的生成具有重要的影响,并给出了畸形波生成的规律。     

基于 mN LS方程的周期波群非线性演化数值模拟研究

论文基于控制深水复波包络演化的修正的四阶非线性薛定谔方程（mNLS）建立模型,利用离散时间步长的虚拟频谱方法（split‐step pseudospectral method）进行求解,模拟了周期波群的非线性演化,对演化过程中复包络幅值、波面位移、谱成分能量以及模态值的变化进行分析。结果表明：该模型可以有效地模拟周期波群的非线性演化。     

基于双层Boussinesq方程的聚焦波数值模型

基于高精度双层Boussinesq方程,建立了聚焦波的时域波浪数值水槽。时间积分采用混合4阶Adams-BashforthMoulton预报-校正格式,聚焦波生成则采用累加不同频率规则波的内部造波源项法。针对Baldock等的聚焦波试验进行数值计算,计算结果与试验数据吻合较好。利用验证后模型进一步考察了非线性对数值计算聚焦波的影响,其中考虑了强非线性、弱非线性以及线性3种情况,结果表明非线性对精确模拟聚焦波至关重要,强非线性模型给出的结果最好,弱非线性次之,线性最差。     

双层Boussinesq水波方程

从Laplace方程出发,推导了一组适应于波浪在非平整地形上传播的双层Boussinesq水波方程,方程以双层水深积分平均速度表达且具有二阶全非线性特征。通过在动量方程中引入高阶色散项和非线性项进一步提高了方程的色散性和非线性性能。常水深情况下,分析了方程的色散关系和二阶波幅传递函数,并与Stokes解析解进行了比较。结果表明,在0.3%误差下方程可适用水深达kh≈6,在此水深范围内二阶波幅传递函数误差在10%以内。在非交错网格下,建立了基于有限差分方法和混合4阶Adams-Bashforth-Moulton时间积分格式的一维数值模型,模拟了波浪在潜堤上的传播变形,并与实验结果进行了对比,吻合程度较好。     

畸形波对圆柱作用力计算的波形改造法

在分析国外一些研究成果为基础上，根据畸形波的记录，提出了通过对波形相近的波浪进行改造，来近似计算畸形波对建筑物波浪力的思想。并以改造Stocks五阶波计算直立圆柱承爱水平作用力为例，说明了其一般步骤。     

三维完全非线性波浪水槽的数值模拟

用有限元求解拉普拉斯方程,采用满足完全非线性自由表面条件的半拉格朗日法追踪流体自由表面,离散单元采用20节点的六面体二次等参数单元,建立了三维完全非线性数值波浪水槽.把数值计算结果与水面初始升高产生箱体内流体运动解析解和二阶斯托克波理论解进行了对比,结果表明该模型是稳定的、守恒的,能精确模拟非线性波浪的产生和传播,为今后研究非线性波浪对船舶等非规则物体的作用提供了参考.     

二维驳船结构在规则波作用下的高频共振响应研究

基于势流理论建立二维完全非线性数值波浪水槽模型,利用该模型对二维驳船结构在非线性规则波作用下的高频共振响应进行了研究.采用高阶边界元方法解决边界值问题,应用混合欧拉-拉格朗日方法和四阶龙格库塔法模拟结构物与波浪的相互作用,引入虚拟函数法耦合求解波浪载荷与物体运动.计算了浮动驳船结构在规则波作用下的运动,并将数值结果与实验值进行了对比验证.当入射波浪的3倍频等于物体横摇方向固有频率时,物体横摇运动发生的高频共振现象,并分析了其影响因素.基于完全非线性数值波浪水槽模型探究了高频共振响应现象的发生机理,为今后海洋工程结构物的高频共振响应问题做有益探索.     

波浪水池中畸形波生成的研究综述

畸形波具有异常大的波高,容易对海洋结构物造成巨大破坏。世界各大海域均有畸形波发生及其引起的海难记录,其生成机理正引起人们越来越多的关注。在实测畸形波时历的基础上,有必要在实验室中实现畸形波的生成,从而揭示畸形波的生成机理及其对海洋结构物的作用机理。目前,国内外许多学者根据畸形波所产生的海洋环境条件提出了多种多样的畸形波成因假说,并相应地形成了多种畸形波生成模型。色散聚集方法通过控制成分波相位使波浪能量定时定点聚集,简单高效,仍为大多数的畸形波生成研究的首选。在此基础上,部分学者提出或应用了迭代方法对畸形波模拟结果进行优化,以修正非线性波波作用引起的相位、幅值偏离。另一方面,薛定谔方程呼吸子解作为畸形波的一个原型,也在畸形波的生成模拟中得到成功应用。该文针对上述畸形波在数值波浪水池或物理水池中的模拟方法作了综述,可为进一步开展畸形波的机理研究及其对海洋结构物作用机理研究提供基础。     

渗透介质中波浪传播的二阶Boussinesq水波数值模拟

准确模拟波浪在多孔介质中传播变形对于研究波浪与抛石防波堤等建筑物是十分必要的,在考虑了多孔介质中拖曳阻力和惯性力的基础上,导出一组高阶Boussinesq型水波方程。在常水深情况下对方程进行了理论研究,并将无因次相速度以及衰减率与解析解结果进行了对比。结果显示方程的相速度与解析解吻合程度较好,同时衰减系数也与解析解在不同程度上吻合较好。在非交错网格下,对方程进行了预报-校正的求解模式。利用一维数值模型模拟了孤立波在多孔介质中的传播,与相关实验结果进行了对比,验证了数值模型的合理性,并且对波浪在渗透地形中的传播进行了数值模拟,数值结果与实验结果吻合较好,验证了多孔介质对波浪的影响。     

Construction of wave-free potentials and multipoles in a two-layer fluid having free-surface boundary condition with higher-order derivatives

There is a large class of problems in the field of fluid structure interaction where higher-order boundary conditions arise for a second-order partial differential equation. Various methods are being used to tackle these kind of mixed boundary-value problems associated with the Laplace’s equation (or Helmholtz equation) arising in the study of waves propagating through solids or fluids. One of the widely used methods in wave structure interaction is the multipole expansion method. This expansion involves a general combination of a regular wave, a wave source, a wave dipole and a regular wave-free part. The wave-free part can be further expanded in terms of wave-free multipoles which are termed as wave-free potentials. These are singular solutions of Laplace’s equation or two-dimensional Helmholz equation. Construction of these wave-free potentials and multipoles are presented here in a systematic manner for a number of situations such as two-dimensional non-oblique and oblique waves, three dimensional waves in two-layer fluid with free surface condition with higher order partial derivative are considered. In particular, these are obtained taking into account of the effect of the presence of surface tension at the free surface and also in the presence of an ice-cover modelled as a thin elastic plate. Also for limiting case, it can be shown that the multipoles and wave-free potential functions go over to the single layer multipoles and wave-free potential.     

具有高阶导数自由表面边界条件的两层流体无波势和多级的构建（英文）

There is a large class of problems in the field of fluid structure interaction where higher-order boundary conditions arise for a second-order partial differential equation. Various methods are being used to tackle these kind of mixed boundary-value problems associated with the Laplace's equation(or Helmholtz equation) arising in the study of waves propagating through solids or fluids. One of the widely used methods in wave structure interaction is the multipole expansion method. This expansion involves a general combination of a regular wave, a wave source, a wave dipole and a regular wave-free part. The wave-free part can be further expanded in terms of wave-free multipoles which are termed as wave-free potentials. These are singular solutions of Laplace's equation or two-dimensional Helmholz equation. Construction of these wave-free potentials and multipoles are presented here in a systematic manner for a number of situations such as two-dimensional non-oblique and oblique waves, three dimensional waves in two-layer fluid with free surface condition with higher order partial derivative are considered. In particular, these are obtained taking into account of the effect of the presence of surface tension at the free surface and also in the presence of an ice-cover modelled as a thin elastic plate. Also for limiting case, it can be shown that the multipoles and wave-free potential functions go over to the single layer multipoles and wave-free potential.     

透空式梳式防波堤的数值模拟和波浪透射系数的研究

基于FLUENT求解器,采用源函数造波方法建立了三维数值波浪水槽,应用不同的造波源函数生成线性波浪、二阶Stokes波浪和不规则波浪.建立了规则波浪和不规则波浪与梳式防波堤相互作用的数值模型,验证了水平波浪力折减系数和堤前反射率的数值结果;并对梳式防波堤有效减小波浪力的机理进行数值解释.对透空式梳式防波堤的透浪特性进行...     

防波堤平面布置对建设用海区波浪场影响的数值模拟

为研究燕窝山工程海域在不同的防波堤平面布置下的波浪场分布特征,应用波作用守恒方程和Boussinesq方程建立了大、小范围的波浪数学模型对工程区附近海域的波浪场进行数值模拟,统计并分析工程前后防波堤附近波浪特征站位的波要素。基于防波堤基本布置方案1,改变防波堤的长度和轴线角度,根据不同平面布置下的防波堤对波浪的掩护效果进行比较分析。结果表明,综合考虑防波堤附近波浪场的变化特征、防波堤特征站位波要素的变化及防波堤的有效掩护面积3个方面,将防波堤轴线以两段堤相交处为圆心逆时针旋转8°,并将直堤向东侧延长100 m,即方案2为优选方案。     

基于改进型Boussinesq方程的二维波浪数值模型

基于改进型Boussinesq方程，在非交错网格下，建立了二维波浪数值模型。模型计算采用了有限差分法，时间格式上采用混合四阶Adams—Bashforth—Mouhon，空间格式上采用了Wei等（1995）给出的格式。数值计算中。采用了内部造渡技术。数值模拟针对3纽经典浅滩地形上波浪传播变形的实验进行，数值计算结果与实验结果吻合较好。验证了数值模型，该模型可期望用于实际港口渡浪预报。     

线性水波理论中远场无波势的构建(英文)

Various water wave problems involving an infinitely long horizontal cylinder floating on the surface water were investigated in the literature of linearized theory of water waves employing a general multipole expansion for the wave potential. This expansion involves a general combination of a regular wave, a wave source, a wave dipole and a regular wave-free part. The wave-free part can be further expanded in terms of wave-free multipoles which are termed as wave-free potentials. These are singular solutions of Laplace’s equation (for non-oblique waves in two dimensions) or two-dimensional Helmholz equation (for oblique waves) satisfying the free surface condition and decaying rapidly away from the point of singularity. The method of constructing these wave-free potentials is presented here in a systematic manner for a number of situations such as deep water with a free surface, neglecting or taking into account the effect of surface tension, or with an ice-cover modelled as a thin elastic plate floating on water.     

直立圆柱体内孤立波载荷特性数值模拟

以三类内孤立波理论(KdV、eKdV和MCC)的适用性条件为依据,将内孤立波诱导上下层深度平均水平速度作为入口条件,采用Navier-Stokes方程为流场控制方程,建立了两层流体中内孤立波对直立圆柱体强非线性作用的数值模拟方法.结果表明,数值模拟所得内孤立波波形及其振幅与相应理论和实验结果一致,并且直立圆柱体内孤立波水平力、垂向力及其力矩数值模拟结果与实验结果吻合.直立圆柱体内孤立波载荷由波浪压差力、粘性压差力和摩擦力构成,其中摩擦力很小,可以忽略;对于水平力,其波浪压差力与粘性压差力量级相当,流体粘性的影响显著;对于垂向力,粘性压差力很小,流体粘性影响可以忽略.此外,直立圆柱体对内孤立波的波形及其诱导流场的影响很小,因此采用Morison公式和傅汝德—克雷洛夫力分别计算其内孤立波水平力和垂向力是可行的.     

Simplified analysis for estimation of the behavior of a submerged floating tunnel in waves and experimental verification

To achieve rational design in waves for a submerged floating tunnel which has emerged as a new offshore transportation infrastructure, it's necessary to understand its hydrodynamic behavior. For simple but accurate estimation of hydrodynamic forces, a theoretical method is proposed and the tests with physical models in a wave flume were carried out for verification. Morison's equation was used to estimate wave loads composed of inertia force and drag force. Forces calculated by applying the linear wave theory to Morison's equation coincided well with those measured by the tests. The test results showed that mooring systems played a significant role in the movement of the submerged floating tunnel in waves. A pendulum model could be used to describe the motion of the submerged floating tunnel with a single vertical mooring. Based on the verified relations, a simple slack condition which causes the submerged floating tunnel to be unstable was also proposed. The simplified approach proposed by this study proved to be useful in designing the submerged floating tunnel in the initial stage.     

基于一个二维修正水弹性方法的集装箱船体梁动态前极限强度评估研究

海上极端波因其巨大的波高常常导致船体的极限破坏。该文提出了一个二维的修正水弹性方法来研究一个集装箱船船体梁在极端波中的动态前极限强度。传统的极限强度评估基于准静态方法,没有动态效应被考虑。而船体在波浪下的动态结构响应是基于水弹性方法,传统的水弹性方法并不能计算船体梁的动态非线性强度。该二维修正的水弹性方法考虑时域波浪和非线性船体梁之间的耦合,将水弹性方法和Smith方法结合,用Smith方法计算船体梁的刚度,而其刚度与船体梁的强度和变形曲率有关。所以该时域的非线性刚度被用于修改水弹性方法里的常数项的结构梁刚度。几组极端波模型被用以产生船体梁的大变形和非线性动态垂向弯矩。文中分别采用修正水弹性方法和普通水弹性方法,通过改变四个重要的极端波参数如极端波最大波高、规则波的波高、波速和波长等来研究其对船体梁船中处的大变形转角和非线性垂向弯矩的影响,通过采用修正的水弹性方法计算得来的结果与水弹性方法计算得来的结果相比较,得到了一些差异和结论。