随机波浪作用下近岸波流场的数值模拟

结合近岸波浪抛物型缓坡模型和近岸波流场模型,对近岸不规则波浪及其破碎后所产生的流场进行了数值模拟. 在不规则波浪场的模拟中,采用JONSWAP波浪谱对入射单向不规则波浪要素按等分频率法进行离散,应用考虑波浪不规则性和破碎效应的抛物型缓坡方程对波浪场进行数值模拟,并基于抛物型缓坡方程中的波浪势函数等参数计算波浪辐射应力,以波浪辐射应力为主要动力因素基于近岸流数学模型对近岸波浪破碎所产生的近岸流场进行数值模拟,并对数值模拟结果进行了验证. 模拟结果表明该模型可有效地用于研究波浪破碎产生的近岸波流场.      

非周期波浪与直墙作用的非线性数值研究

基于时域高阶边界元方法,建立了完全非线性二维数值波浪水槽,对非周期波浪与直墙的相互作用问题进行了模拟和研究.自由表面满足完全非线性自由水面运动学和动力学边界条件,采用混合欧拉-拉格朗日方法追踪瞬时自由面流体质点,采用四阶Runge-Kutta法对下一时间步的波面和自由面速度势进行更新.采用加速度式法求解直墙表面速度势的时间导数,对瞬时物体湿表面上的水动力压强积分,得到作用在物体上的瞬时波浪力.首先,将全非线性与Serre-Green-Naghdi(SGN)模型的结果进行了对比分析,发现对于大幅值双入射波问题,仅满足弱色散关系的SGN模型大大低估了最大波浪爬高;其次,研究了双入射波与直墙的非线性作用问题,发现线性预报对波浪最大爬高有较大低估,而波浪的非线性成分不只导致了自由面爬高的异常增大,也引起了局部自由面的高频振荡,该物理过程中,直墙所受的波浪载荷,也展示出了与波浪爬高相似的非线性特性;最后,对波浪爬升和波浪力的时间历程进行了频谱分析,发现入射主频波的部分能量传递给了更高频的波浪成分,反映出该问题具有典型的非线性特性.     

基于Boussinesq方程的波浪模型

从欧拉方程出发，提供了另一种推导完全非线性Boussinesq方程的方法，并对方程的 线性色散关系和线性变浅率进行了改进. 改进后方程的线性色散关系达到了一阶Stokes波 色散关系的Pad\'{e}[4,4]近似，在相对水深达1.0的强色散波浪时仍保持较高的准确性，并且方程的非线性和线性 变浅率都得到了不同程度的改善. 方程的水平一维形式用预估-校正的有限差分格式求解， 建立了一个适合较强非线性波浪的Boussinesq波浪数值模型. 作为验证，模拟了波浪在潜 堤上的传播变形，计算结果和实验数据的比较发现两者符合良好.     

非结构化网格下大范围波浪的折绕射计算

从含流缓坡方程出发,推导出光程函数方程。采用基于非结构化网格下的有限体积法对光程函数方程和波作用守恒方程进行数值离散和联合求解,从而构建了一个考虑绕射的计算近岸大范围波浪传播过程的数值模型。模型的空间步长不再受制于波长的限制,同时非结构化网格可以很好地拟合复杂岸线变形。模型分别通过了施奈尔定律、直立防波堤后的波浪绕射和圆形浅滩上的波浪变形验证,结果表明,该数值模式能有效模拟复杂边界条件和大范围水域下近岸波浪的传播过程中的折射和绕射等变形。     

波浪破碎的一种混合湍流模拟模式

近岸波浪的变形与破碎,一方面影响水体标识码运输,另一方面对消波护岸具有指导意义.本文提出一种三维混合湍流模拟模式方法,将求解区域分为造波区、波浪传播区和消波区. 造波区采用层流模式,通过基于 Fluent 的二次开发的 UDF 方法在边界进行速度造波.这种方法在给定入口速度的条件标识码据已知波高进行 精准插值,从而控制水的体积分数. 在波浪传播区域,采用大涡标识码行模拟研究,在消波区,采用 RANS 模型并利用多孔介质消波法进行消波. 模标识码 VOF 方法捕捉波浪破碎过程中的自由面变化.本文对波高为 5.5cm 的规则波 (M1)、波高为 13.5cm 的 规则波 (M3)、有效标识码 7.75cm 的 TMA 谱单向不规则波 (U1) 和有效波高为 19cm 的 TMA 谱多向不规则波 (B5) 展开标识码研究,并与前人的相关标识码果作比较,各条件下模拟结果与实验结果吻合.模拟结果说明本文提出的模型能够准确模拟出波浪传播过程中的折射和标识码象,并且能够捕捉的波浪破碎过程中的自由面变化,为三维波浪的传播与破碎的数值模拟提供一种模拟方法.      

具有精确色散性的非线性波浪数学模型

以完全非线性的自由表面边界条件为基础,以波面升高\eta和自由表面速度势\phi _\eta为待求变量,建立了新的波浪方程．方程在色散性上是完全精确的,非线性近似至三阶．与缓坡方程相比较,两者都具有精确的色散性,但该方程属于非线性模型,可模拟波浪的非线性效应,且适用于不规则波．方程的特点是属于微分-积分方程,对如何处理方程中积分项进行了讨论,并数值模拟了不同周期的线性波和二阶Stokes波,也模拟了波群的非线性演化,以对模型进行验证．      

海堤越浪的数值模拟

基于RANS方程和两方程湍流模型，采用有限体积法，将人射波波场作为人工的分布源项加人动量方程，提出了适用于VOF方法的源造波一消波技术。通过对行波及驻波的计算，分别考察了数值波浪水槽前端及末端消波段的有效性。在本文建立的数值波浪水槽内对规则波在海堤上爬高和越浪过程进行了数值模拟，并将计算结果与现有实验结果进行了比较。验证计算结果表明，数值模拟结果较好地复演了海堤越浪过程。为了研究模型尺度对越浪量的影响，文中设计了一组满足重力相似但具有不同几何比尺的数值实验模型。系列数值实验结果表明，若按重力相似换算越浪量，计算结果与实验预报值间的偏差随模型比尺的增大和堤前波浪破碎强度的增强而增大，建议在进行越浪物理模型实验时需进一步考虑模型比尺对原型预报值的影响。     

潜堤对波浪在直立式防浪墙上爬高的影响

对直立式防浪墙前潜堤的空间布置对波浪在直墙上爬高的影响进行了研究.建立简化模型,即直立式防浪墙前海床设计为平底,潜堤设计为直立薄板. 改变潜堤高度及其与防浪墙之间距,研究不同的潜堤布置对波浪在直墙上爬高的影响. 针对线性波浪场,利用数值波浪水槽模拟了潜堤作用下直墙上波浪的爬高现象. 同时建立了理论模型,系统地分析了潜堤布置形式对直墙上波浪爬高的影响. 研究结果表明潜堤相对于水深的高度越大,对波浪在直墙上爬高的影响越大,而在一定的相对高度条件下,潜堤与直立墙之间距对波浪爬高的影响呈现出一定的规律性.      

海岸碎波拍的计算

研究了一维碎波拍的计算方法．波浪控制方程由欧拉方程在短波周期上平均而得到．为了考虑低频波浪在海岸上的破碎，采用了ＷＡＦ（ＷｅｉｇｈｔｅｄＡｖｅｒａｇｅＦｌｕｘ）方法求解长波方程．对由辐射应力和海底摩擦力引起的方程非齐次项采用了时间算子分裂法进行了处理，并对由此产生的误差进行了修正．计算了单色波和双色波垂直入射海岸的情况，并与实验结果进行了对比．     

液滴在气体介质中剪切破碎的数值模拟研究

液滴变形和破碎是燃料抛撒问题的重要过程.本文将VOF方法和标准k-ε湍流模型组合,建立了计算液滴在气流中变形破碎过程的数值方法.数值模拟了相关的实验,计算得到的液滴破碎过程与实验结果符合较好.在此基础上,分析了几个关键参数(Weber数、Ohnesorge数、液气密度比)对液滴破碎过程的影响.计算结果表明,Weber数...     

Numerical study of breaking waves by a two‐phase flow model

A two‐phase flow model, which solves the flow in the air and water simultaneously, is presented for modelling breaking waves in deep and shallow water, including wave pre‐breaking, overturning and post‐breaking processes. The model is based on the Reynolds‐averaged Navier–Stokes equations with the k ?ε turbulence model. The governing equations are solved by the finite volume method in a Cartesian staggered grid and the partial cell treatment is implemented to deal with complex geometries. The SIMPLE algorithm is utilised for the pressure‐velocity coupling and the air‐water interface is modelled by the interface capturing method via a high resolution volume of fluid scheme. The numerical model is validated by simulating overturning waves on a sloping beach and over a reef, and deep‐water breaking waves in a periodic domain, in which good agreement between numerical results and available experimental measurements for the water surface profiles during wave overturning is obtained. The overturning jet, air entrainment and splash‐up during wave breaking have been captured by the two‐phase flow model, which demonstrates the capability of the model to simulate free surface flow and wave breaking problems.Copyright © 2011 John Wiley & Sons, Ltd.     

Numerical simulation of pollutant transport acted by wave for a shallow water sea bay

A numerical model of pollutant transport acted by water waves on a shallow‐water mild‐slope beach is established in this study. The numerical model is combined with a wave propagation model, a multiple wave‐breaking model, a wave‐induced current model and a pollutant convection–dispersion model. The wave propagation model is based on the higher‐order approximation of parabolic mild‐slope equation which can be used to simulate the wave refraction, diffraction and breaking in a large area of near‐shore zone combined with the wave‐breaking model. The wave‐induced current model is established using the concept of the radiation stress and considering the effect of bottom resistance caused by waves. The numerical model is verified by laboratory experiment results of regular and irregular waves over two mild beaches with different slopes. The numerical results agree well with experimental results. The numerical model has been applied in the near‐shore zone of Bohai bay in China. It is concluded that pollutant transport parallel to the shoreline due to the action of waves, which will induce serious pollution on the beach. Copyright © 2005 John Wiley & Sons, Ltd.     

Two-dimensional bifurcations of stokes waves

Bifurcation techniques are used to obtain a new class of small amplitude water waves of permanent form. This calculation illustrates an approach which can be applied to nonlinear waves of various types to generate new steady solutions from old.Stokes waves are used as a starting point, and the critical value of steepness at which bifurcation can occur is computed for various choices of modulation wavelength and angular orientation. It is found that, for two-dimensional surfaces, bifurcation can occur at small values of wave steepness.Second-order corrections to the wave amplitude, modulation, frequency, and speed, which apply when one moves off the bifurcation point onto a new branch of solutions, are also computed. Two types of new solutions are found, one symmetric with respect to the carrier wave propagation direction, and one asymmetric.The nonlinear Schrödinger equation is used to model water waves, and thus the calculation can be applied rather directly to other systems governed by the nonlinear Schrödinger equation.     

A new numerical model for simulations of wave transformation,breaking and long‐shore currents in complex coastal regions

In this paper, we propose a model based on a new contravariant integral form of the fully nonlinear Boussinesq equations in order to simulate wave transformation phenomena, wave breaking, and nearshore currents in computational domains representing the complex morphology of real coastal regions. The aforementioned contravariant integral form, in which Christoffel symbols are absent, is characterized by the fact that the continuity equation does not include any dispersive term. A procedure developed in order to correct errors related to the difficulties of numerically satisfying the metric identities in the numerical integration of fully nonlinear Boussinesq equation on generalized boundary‐conforming grids is presented. The Boussinesq equation system is numerically solved by a hybrid finite volume–finite difference scheme. The proposed high‐order upwind weighted essentially non‐oscillatory finite volume scheme involves an exact Riemann solver and is based on a genuinely two‐dimensional reconstruction procedure, which uses a convex combination of biquadratic polynomials. The wave breaking is represented by discontinuities of the weak solution of the integral form of the nonlinear shallow water equations. The capacity of the proposed model to correctly represent wave propagation, wave breaking, and wave‐induced currents is verified against test cases present in the literature. The results obtained are compared with experimental measures, analytical solutions, or alternative numerical solutions. Copyright © 2015 John Wiley & Sons, Ltd.     

线性与非线性流固耦合动力学数值方法的进展及应用

本文综述了线性与非线性流固耦合问题数值方法的进展及工程应用。讨论了四种数值分析方法：(1)混合有限元–子结构–子区域数值模型,以求解有限域线性流固耦合问题,如流体晃动,声腔–结构耦合,流体中的压力波,化工容器的地震响应,坝水耦合等;(2)混合有限元–边界元数值模型,以求解涉及无限域的线性流固耦合问题,如大型浮体承受飞机降落冲击,船舰的炮击回应等;(3)混合有限元–有限差分(体积)数值模型,以求解不涉及破浪和两相分离的非线性流固耦合问题;(4)混合有限元–光滑粒子数值模型,以求解涉及破浪和两相分离的非线性流固耦合问题。文中推荐分区迭代求解过程,以便应用现有的固体及流体求解器,于毎一时间步长分别求解固体及流体的方程,通过耦合迭代收敛,向前推进以达问题求解。文中选用的工程应用例子包含气–液–壳三相耦合,液化天然气船水晃动,人体步行冲击引起的声腔–建筑结构耦合,大型浮体承受飞机降落冲击的瞬态动力回应,涉及破浪和两相分离的气–翼耦合及结构于水上降落的冲击。数值分析结果与可用的实验或计算结果作了比较,以说明所述方法的精度及工程应用价值。文中列出了基于流固耦合的波能采积装置模型,以应用线性系统的共振及非线性系统的周期解原理,有效地采积波能。本文列出了231篇参考文献,以便读者进一步研讨所感兴趣方法。     

Developments of numerical methods for linear and nonlinear fluid-solid interaction dynamics with applications

本文综述了线性与非线性流固耦合问题数值方法的进展及工程应用. 讨论了四种数值分析方法: (1) 混合有限元-子结构-子区域数值模型, 以求解有限域线性流固耦合问题, 如流体晃动, 声腔-结构耦合, 流体中的压力波, 化工容器的地震响应,坝水耦合等; (2) 混合有限元-边界元数值模型, 以求解涉及无限域的线性流固耦合问题, 如大型浮体承受飞机降落冲击, 船舰的炮击回应等; (3) 混合有限元-有限差分(体积) 数值模型, 以求解不涉及破浪和两相分离的非线性流固耦合问题; (4) 混合有限元-光滑粒子数值模型, 以求解涉及破浪和两相分离的非线性流固耦合问题. 文中推荐分区迭代求解过程, 以便应用现有的固体及流体求解器, 于毎一时间步长分别求解固体及流体的方程, 通过耦合迭代收敛, 向前推进以达问题求解. 文中选用的工程应用例子包含气-液-壳三相耦合, 液化天然气船水晃动, 人体步行冲击引起的声腔-建筑结构耦合, 大型浮体承受飞机降落冲击的瞬态动力回应, 涉及破浪和两相分离的气-翼耦合及结构于水上降落的冲击. 数值分析结果与可用的实验或计算结果作了比较, 以说明所述方法的精度及工程应用价值. 文中列出了基于流固耦合的波能采积装置模型, 以应用线性系统的共振及非线性系统的周期解原理, 有效地采积波能. 本文列出了231 篇参考文献, 以便读者进一步研讨所感兴趣方法.     

非线性周期波及破碎波对杆件的作用力

本文采用十五阶 Stokes 波的 Pade 逼近,获得了与实验较为一致的流场,并且利用已有的破碎波的速度、加速度场,计算了非线性波和破碎波对各种杆件作用力,比较了它们的主要特征,为海洋工程设计提供依据。     

Generation of two-dimensional steep water waves on finite depth with and without wind

This paper reports on a series of numerical simulations designed to investigate the action of wind on steep waves and breaking waves generated through the mechanism of dispersive focusing on finite depth. The dynamics of the wave packet propagating without wind at the free surface are compared to the dynamics of the packet propagating in the presence of wind. Wind is introduced in the numerical wave tank by means of a pressure term, corresponding to the modified Jeffreys' sheltering mechanism. The wind blowing over a strongly modulated wave group due to the dispersive focusing of an initial long wave packet increases the duration and maximal amplitude of the steep wave event. These results are coherent with those obtained within the framework of deep water. However, steep wave events are less unstable to wind perturbation in shallow water than in deep water.Furthermore, a comparison between experimental and numerical wave breaking is presented in the absence of wind. The numerical simulations show that the wind speeds up the wave breaking and amplifies slightly the wave height.The wall pressure during the runup of the steep wave event on a vertical wall is also investigated and a comparison between experimental and numerical results is provided.     

关于海洋结构物水动力学的研究

建造在海洋中的结构物承受波浪、海流、风、地震等作用力,其中尤以波浪力最为重要且复杂。迄今,在小构件海洋结构物波浪力设计计算中,最普遍使用的仍然是Morison方程。但是,这里所说的Morison方程已经不是Morison等的原始方程,而是各种扩展情况下的Morison方程。当初Morison等把由粘性流体得到的阻力项和由理想流体得到的惯性力项相加即得到总波浪力,这种把同一流体既看成是粘性流体又看成是非粘性不可压缩的理想流体的做法实属自相矛盾。但是,建立Morison方程30多年以来,其改进只限于形式稍有      

A new σ‐transform based Fourier‐Legendre‐Galerkin model for nonlinear water waves

This paper presents a new spectral model for solving the fully nonlinear potential flow problem for water waves in a single horizontal dimension. At the heart of the numerical method is the solution to the Laplace equation which is solved using a variant of the $\sigma$‐transform. The method discretizes the spatial part of the governing equations using the Galerkin method and the temporal part using the classical fourth‐order Runge‐Kutta method. A careful investigation of the numerical method's stability properties is carried out, and it is shown that the method is stable up to a certain threshold steepness when applied to nonlinear monochromatic waves in deep water. Above this threshold artificial damping may be employed to obtain stable solutions. The accuracy of the model is tested for: (i) highly nonlinear progressive wave trains, (ii) solitary wave reflection, and (iii) deep water wave focusing events. In all cases it is demonstrated that the model is capable of obtaining excellent results, essentially up to very near breaking.