直立码头前船波浪力耦合计算模型

建立了外域用Boussinesq方程、内域用刚体运动方程的直立码头前二维船剖面波浪力的时 域计算耦合模型,内域与外域在交界面的匹配条件是流量连续和压力相等. 进行了相关模型 实验,并把计算结果与实验结果进行了对比. 推导了船体与水底和直立码头之间间隙内流体 运动的自振频率,研究了间隙内流体运动的共振现象.     

Reflection of a Dam–Break Wave at a Vertical Wall. Numerical Modeling and Experiment

Results of the experimental study and numerical modeling of the reflection of a dam–break wave at the vertical end wall of a channel are given. A wave forms with distance from a partition creating the initial level difference of the liquid. It is shown that a numerical calculation based on the Zheleznyak—Pelinovskii nonlinear dispersion model satisfactorily describes the height of the splash–up, the amplitude of reflected waves, and the wave velocity in front of the wall for smooth and dam–break waves. It is also shown that, for smooth and weakly breaking (without significant entrainment of air) incoming waves, the experimental values of the height of the splash–up at the wall agree well with relevant experimental and calculated data for solitary waves.     

等波高双孤立波直墙爬高的数值模拟

基于RANS方程、VOF方法以及修正的Goring造波方法建立了模拟活塞式推波板运动的二维数值波浪水槽,实现了双孤立波直墙爬高的数值模拟．利用动边界技术模拟造波机推波板的运动,有效地实现了不同波峰间距双孤立波的造波方法．在验证单孤立波直墙爬高的基础上,模拟了不同相对波高、相对波峰间距的等波高双孤立波的直墙爬高过程,给出了波面、速度场及波动能量的变化规律．数值模拟结果表明：对于等波高的双孤立波,当入射波波高较大及两个波峰间距相对较小时,跟随在后孤立波的爬高放大系数小于先导孤立波的爬高放大系数;双孤立波在直墙爬高过程中,波动场的势能时间过程线呈现三峰形态,其中居中的最大势能峰值出现在第二个孤立波与经直墙反射后反向传播的第一个孤立波完全对撞的时刻．     

Nonlinear faraday waves in a parametrically excited circular cylindrical container

IntroductionIn 1 83 1 ,Faraday[1]reportedhisexperimentalobservationofsurfacewavesindifferentfluidscoveringahorizontalplatesubjectedtoaverticalvibration ,andheobservedthesurfacestandingwavesoffluidsliketheteethofaveryshortcoarsecomb .Heremarksthatthesesurfacewaveshaveafrequencyequaltoonehalfthatoftheexcitation .ThisisthefamousFaradayexperiment.WedesignatethosefluidsurfacewavesformedbyverticallyexcitationandhaveafrequencyequaltoonehalfthatoftheexcitationasFaradaywaves.FollowingthisproblemMatth…     

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。     

波浪作用下直立结构物附近强湍动掺气流体运动的数值模拟

波浪破碎卷入气体易对建筑物受力产生压力振荡,了解波浪作用下建筑物附近掺气水流的运动特性是精确计算建筑物受力的前提.基于OpenFOAM开源程序包和修正速度入口造波方法建立三维数值波浪水槽,模型采用S-A IDDES湍流模型进行湍流封闭,并采用修正的VOF方法捕捉自由液面,数值模拟了规则波在1:10的光滑斜坡上与直立结构物的相互作用过程,重点分析了结构物附近的水动力和掺气水流运动特性.结果表明,建立的数值模型能精确地捕捉波浪作用下直立结构物附近的自由液面的变化以及气泡输运过程,较好地描述气体卷入所形成的气腔形态以及多气腔之间的融合、分裂等过程;波浪与直立结构物相互作用产生强湍动掺气水流,其运动过程十分复杂;掺气流体输运过程中水气界面周围一直伴随着涡的存在,其中,气泡的分裂与周围正负涡量剪切作用密切相关,且其输运轨迹主要受周围流场的影响;研究揭示了结构物附近湍动能与掺气特性的关系,发现波浪作用下直立结构物附近湍动能的分布与掺气水流特征参数(气泡数量、空隙率)整体呈现一定的线性关系.     

Breaking and cascade of internal gravity waves in a continuously stratified fluid

The evolution of a few large scale high frequency standing internal waves confined to a vertical plane is studied numerically. The growth of nonlinear interactions leads to a transfer of energy toward small vertical scales and lower frequencies: the result is a steep energy decrease due to wave breaking. Induced mixing is evaluated. A parametric forcing is also introduced in order to compare with laboratory experiments. Wave breaking also occurs but as opposed to the unforced case different phases are next observed: internal wave growth due to constructive forcing alternate with energy decrease.     

Green water impact pressure on a three-dimensional model structure

Green water impact pressure due to plunging breaking waves impinging on a simplified, three-dimensional model structure was investigated in the laboratory. Two breaking wave conditions were tested: one with waves impinging on the vertical wall of the model at the still water level and the other with waves impinging on the horizontal deck surface. Pressure measurements were taken at locations in two vertical planes on the deck surface with one at centerline of deck and the other between the centerline and an edge. Impact pressure was found to be quite different between the two wave conditions even though the incoming waves are essentially identical. Two types of pressure variations were observed??impulsive type and non-impulsive type. Much higher pressure was observed for the deck impingement wave condition, even though the flow velocities were quite close. Void fraction was also measured at selected points. Impact pressure was correlated with the mean kinetic energy calculated based on the measured mean velocities and void fraction. Impact coefficient, defined as the ratio between the maximum pressure at a given point and the corresponding mean kinetic energy, was obtained. For the wall impingement wave condition, the relationship between impact pressure and mean kinetic energy is linear with the impact coefficient close to 1.3. For the deck impingement wave condition, the above relationship does not show good correlation; the impact coefficient was between 0.6 and 7. The impact coefficient was found to be a function of the rate of pressure rise.     

Three-dimensional green water velocity on a model structure

Flow kinematics of green water due to plunging breaking waves impinging on a simplified, 3D model structure was investigated in the laboratory. Two breaking wave conditions were tested: one with waves impinging on the vertical wall of the model at still water level, and the other with waves impinging on the horizontal deck surface. The bubble image velocimetry (BIV) technique was used to measure flow velocities. Measurements were taken on both vertical and horizontal planes. Evolution of green water flow kinematics in time and space was revealed and was found to be quite different between the two wave conditions, even though the incoming waves are essentially identical. The time history of maximum velocity is demonstrated and compared. In both cases, the maximum velocity occurs near the green water front and beneath the free surface. The maximum horizontal velocity for the deck impinging case is 1.44C with C being the wave phase speed, which is greater than 1.24C for the wall impingement case. The overall turbulence level is about 0.3 of the corresponding maximum velocity in each wave condition. The results were also compared with 2D experimental results to examine the 3D effect. It was found that the magnitude of the maximum vertical velocity during the runup process is 1.7C in the 3D model study and 2.9C in the 2D model study, whereas the maximum horizontal velocity on the deck is similar, 1.2C in both 3D and 2D model studies.     

Standing surface waves in a rectangular tank with local wall and bottom irregularities

The results of laboratory experiments on the estimation of the effect of wall and bottom geometry on the frequency, height, and decay rate of standing surface waves in a tank oscillating in the vertical direction are presented. The effect of one or two semi-cylindrical inserts mounted on the face and rear walls of the tank is considered in detail for the cases of a horizontal bottom and a linear shallow on the bottom. The experimental data are interpreted using a mathematical longwave model based on the method of accelerated convergence.     

Motion of a vertical wall fixed on springs under the action of surface waves

A two-dimensional unsteady hydroelastic problem of interaction between surface waves and a moving vertical wall fixed on springs is studied. An analytical solution of the problem is constructed using a linear approximation, and a numerical solution within the framework of a nonlinear model of a potential fluid flow is found by a complex boundary element method. By means of analysis of the linear and nonlinear solutions, it is found that the linear solution can be used to predict some important characteristics of the wall motion and the fluid flow in the case of moderate wave amplitudes.     

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.     

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.     

A depth‐integrated non‐hydrostatic finite element model for wave propagation

This paper presents a two‐dimensional finite element model for simulating dynamic propagation of weakly dispersive waves. Shallow water equations including extra non‐hydrostatic pressure terms and a depth‐integrated vertical momentum equation are solved with linear distributions assumed in the vertical direction for the non‐hydrostatic pressure and the vertical velocity. The model is developed based on the platform of a finite element model, CCHE2D. A physically bounded upwind scheme for the advection term discretization is developed, and the quasi second‐order differential operators of this scheme result in no oscillation and little numerical diffusion. The depth‐integrated non‐hydrostatic wave model is solved semi‐implicitly: the provisional flow velocity is first implicitly solved using the shallow water equations; the non‐hydrostatic pressure, which is implicitly obtained by ensuring a divergence‐free velocity field, is used to correct the provisional velocity, and finally the depth‐integrated continuity equation is explicitly solved to satisfy global mass conservation. The developed wave model is verified by an analytical solution and validated by laboratory experiments, and the computed results show that the wave model can properly handle linear and nonlinear dispersive waves, wave shoaling, diffraction, refraction and focusing. Copyright © 2013 John Wiley & Sons, Ltd.     

Non‐hydrostatic 3D free surface layer‐structured finite volume model for short wave propagation

In this paper a layer‐structured finite volume model for non‐hydrostatic 3D environmental free surface flow is presented and applied to several test cases, which involve the computation of gravity waves. The 3D unsteady momentum and mass conservation equations are solved in a collocated grid made of polyhedrons, which are built from a 2D horizontal unstructured mesh, by just adding several horizontal layers. The mesh built in such a way is unstructured in the horizontal plane, but structured in the vertical direction. This procedure simplifies the mesh generation and at the same time it produces a well‐oriented mesh for stratified flows, which are common in environmental problems. The model reduces to a 2D depth‐averaged shallow water model when one single layer is defined in the mesh. Pressure–velocity coupling is achieved by the Semi‐Implicit Method for Pressure‐Linked Equations algorithm, using Rhie–Chow interpolation to stabilize the pressure field. An attractive property of the model proposed is the ability to compute the propagation of short waves with a rather coarse vertical discretization. Several test cases are solved in order to show the capabilities and numerical stability of the model, including a rectangular free oscillating basin, a radially symmetric wave, short wave propagation over a 1D bar, solitary wave runup on a vertical wall, and short wave refraction over a 2D shoal. In all the cases the numerical results are compared either with analytical or with experimental data. Copyright © 2008 John Wiley & Sons, Ltd.     

驻定斜爆轰波并行数值模拟

采用多组分化学反应Euler方程组对驻定在高速飞行弹丸上的斜爆轰波流场进行了数值模拟。计算中分别采用TVD格式和基元反应模型,并基于并行编程模型MPI（message passing interface）实现了非结构网格上的并行计算,对流项和化学反应项用时间分裂法进行处理。计算结果表明并行计算能有效地提高计算速度,扩展计算规模,为进一步研究超驱爆轰推进技术奠定基础。     

孤立波与多孔介质结构物的非线性相互作用

基于精确至Ｏ（εμ＾２,μ＾４）的多孔介质无压渗流模型方程和均匀流体质波动的Ｂｏｕｓｓｉｎｅｓｑ方程,本文对孤立波与多孔介质结构物的相互作用了较系统的数值实验。控制方程采用基于有限差分方程离散,在时域上采用了预估－校正方法进行了时间积分。在求解演化方程的过程中,引入“内迭代”过程实现流体域和多孔介质交界面的连接条件。结果表明孤立波在多孔介质上的反射与在不可渗透的界面上的反射类似,形成反向的孤立波但     

Bifurcations of two-dimensional into three-dimensional wave regimes for a vertically flowing liquid film

The three-dimensional steady traveling wave regimes of a viscous liquid film flowing down a vertical wall which branch off from two-dimensional nonlinear waves are investigated. The numerical calculations are based on a model system of equations valid for intermediate Reynolds numbers. It is shown that there exist two fundamentally different types of three-dimensional steady traveling waves branching off from plane waves. One of these possesses checkerboard symmetry in the distribution of the maxima of the wave profile thickness and is the more interesting. An important difference in the breakdown of plane waves of the first and second families is also demonstrated. The wave characteristics of certain three-dimensional regimes are calculated as functions of the bifurcation parameter.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 109–114, September–October, 1990.