波浪在陡坡上的传播变化

利用数值方法和物理模型分析以反射为主的陡坡上波浪传播变形特征。数值方法采用标记单元法,为处理倾斜反射边界对斜坡前波浪运动的影响,提出了“台阶镜像法”。通过１：１．５光滑斜坡上物理模型试验,分析了不完全立波的运动特性,说明强反射光滑陡坡坡前波浪运动呈明显的立波状态,它与直墙反射的主要判别是坡前第一波节点和腹点位置向岸推移。本试验得到的波浪反射、爬高和回落特征值与港口工程规范给定结果接近。     

斜坡平台波浪破碎数值模拟

波浪在斜坡地形上破碎,破波后稳定波高多采用物理模型试验方法进行研究,利用近岸波浪传播变形的抛物型缓坡方程和波能流平衡方程,导出了适用于斜坡上波浪破碎的数值模拟方法。首先根据波能流平衡方程和缓坡方程基本型式分析波浪在破波带内的波能变化和衰减率,推导了波浪传播模型中波能衰减因子和破波能量流衰减因子之间的关系;其次,利用陡坡地形上的高阶抛物型缓坡方程建立了波浪传播和波浪破碎数学模型;最后,根据物理模型试验实测数据对数值模拟的效果进行验证。数值计算与试验资料比较表明,该模型可以较好地模拟斜坡地形的波浪传播波高变化。     

波浪与多孔介质结构相互作用SPH模拟

应用经CSPM法和黎曼解修正后的光滑粒子流体动力学(SPH)方法,建立了主动吸收无反射数值波浪水槽,研究波浪作用下多孔介质结构的水动力特性。流体运动控制方程采用N-S方程,多孔渗水结构内流体的运动控制方程考虑渗流力的影响。数值计算结果给出了水槽内不同位置测点的波面历时曲线和越浪量随时间变化曲线,并同试验结果和Philip Liu的数值计算结果进行了比较。并对一个波浪周期内斜坡堤多孔介质结构内外的速度场和压力分布进行了讨论分析。计算分析表明,数值计算波面较Philip Liu的计算结果与试验结果吻合更好。说明应用SPH方法建立的二维数学模型能够较好地模拟破碎波在多孔渗水斜坡上的爬坡和越浪。     

不完全立波的二维数值波浪水槽模拟

利用二维数值波浪水槽研究波浪在防波堤前的运动状态.模型选用Navier-Stokes方程作为基本方程,以有限元法对基本方程进行离散.以直立堤前完全立波和越浪条件的不完全立波、斜坡堤前的不完全立波等典型情况的模拟为基础,组合这些典型情况模拟削角堤前不完全立波运动,探讨其堤前波面、波节点及波腹点位置、波压力等特性变化.     

陡坡上孤立波爬高的数值模拟

波浪爬高是海岸工程中重要的水动力学问题之一,其数值模拟方法通常是通过离散Navier-Stokes方程或Boussinesq方程实现的,其中基于光滑粒子流体动力学方法是近年发展起来的。本文应用该方法模拟相同水深下,不同波高的孤立波在45(°)陡坡上的爬高,模拟结果与理论计算结果及已有物理模型试验结果进行了对比,并模拟出孤立波激散破碎过程及粒子分布和速度场的变化过程。结果表明,对密度近似方程进行重新初始化保持了流场内的质量守恒,同时整个计算域内的压力分布更加规则,说明光滑粒子流体动力学法在波浪爬高计算中的有效性。     

斜坡上波浪破碎与越浪非静压数值模拟

为合理确定防浪建筑物的越浪量,基于含非静水压力梯度项的非线性浅水方程建立了近岸波浪越浪数值模型。通过采用域内造波、消波并结合波前静压假定的破碎模型,模拟了规则波和不规则波在斜坡上的波浪传播变形,并在此基础上进行了越浪量数值计算。数值计算结果与物理模型实验结果表明,非静压模型可合理地描述波浪破碎点位置、破碎后的波高、增减水以及斜坡上的堤后越浪量。数值模型具有较高的计算精度和计算效率,可为实际工程防浪建筑物越浪以及堤顶高程的设计提供一种新的数值研究手段。     

多向随机波浪反射的试验研究

试验研究了多向随机波浪在直立式防波堤和斜坡式防波堤前的反射情况。在试验中，改变波浪要素(波陡、周期)、波浪入射角度(正向、斜向)和方向分布以及防波堤的坡度，以充分研究这些因素对波浪反射的影响。遗传算法用来分析多向随机波从建筑物的反射。试验结果表明，直立堤的反射系数基本上不随入射波浪方向变化，斜坡堤的反射系数随波浪峰频的增大和堤坡的变缓而减小，且随波浪方向有一定变化。还探讨了多向随机波浪在斜坡式防波堤上的反射面位置问题。     

多消浪室开孔沉箱消浪特性的数值模拟研究

本文基于雷诺平均的Navier-Stokes方程和k-ε模型求解湍流流动,采用流体体积法(Volume of Fluid,VOF)追踪自由表面运动,建立无反射波浪数值水槽,对多消浪室开孔沉箱的消浪特性进行数值模拟研究.将单消浪室和多消浪室开孔沉箱反射系数和结构前波面分布的数值分析结果与物理模型试验结果进行对比验证,两者...     

破碎立波对直墙建筑物作用机理的研究

建立二维非线性数值波浪水槽,模拟了规则波条件下破碎立波对直墙建筑物的作用.从直墙上压力分布和各测点的压力过程线等方面与物理模型实验结果进行比较,讨论了破碎立波的作用特点,分析了压力过程线出现马鞍形变化的原因.将破碎立波波浪力与按规范方法和立渡理论方法计算的结果进行了比较.通过对计算结果的的分析比较,验证了该数值模型的有效性.     

港域波浪数学模型的改进与验证

通过物理模型对改进的港内波浪传播变形数学模型进行验证。该数学模型以推广的时变缓坡方程为控制方程,采用含松弛因子的ADI法求解,并对波浪反射和透射边界模拟方法进行改进。先通过物理模型试验确定斜向浪入射条件下抛石防波堤前的波浪反射系数,作为数学模型中部分反射边界模拟的依据。然后进行了一个典型港口内波浪折射、绕射和反射的模型试验,测量港内波浪分布。对比模型试验和数学模型计算的结果表明,数学模型可较好地模拟港内复杂地形和边界条件下规则波和不规则波的传播变形。     

中咀湾避风港工程波浪分析及其应用

中咀湾是一个天然的避风良港,一般情况下外海波浪影响很小,主要受局部风场产生的局部风浪影响。本文采用曹宏生在Massel的扩展缓坡方程基础上推导出来的考虑陡变地形和能量耗散效应的缓坡方程为控制方程,结合固边界的反射边界条件,构成波浪传播变形的联合折射、绕射和反射的数学模型。文中将此方法运用在中国台州市大陈岛中咀湾避风港中,用波浪数学模型计算极端高水位和设计高水位时3种波况分别在3组重现期时工程海域的波浪要素,提供防波堤的堤前波高,并分析比较此处实心式和透空式防波堤的防浪性能。     

Verification of A Numerical Harbour Wave Model

A numerical model for wave propagation in a harbour is verified by use of physical models.The extended time-dependent mild slope equation is employed as the governing equation,and the model is solved by use of ADI method containing the relaxation factor.Firstly,the reflection coefficient of waves in front of rubble-mound breakwaters under oblique incident waves is determined through physical model tests,and it is regarded as the basis for simulating partial reflection boundaries of the numerical model.Then model tests on refraction,diffraction and reflection of waves in a harbour are performed to measure wave height distribution.Comparative results between physical and numerical model tests show that the present numerical model can satisfactorily simulate the propagation of regular and irregular waves in a harbour with complex topography and boundary conditions.     

Transparent boundary condition for simulating nonlinear water waves by a particle method

Open boundaries are important when simulating water waves. In this study, a transparent boundary condition at an open boundary was developed for simulating nonlinear water waves propagating to a distant area using the Moving Particle Semi-implicit method. The novelty of this study is that the technique of wave analysis used in the experiment was introduced into the particle simulation to absorb incident waves; the simulation cost was reduced by employing inflow and outflow regions instead of a long dissipation region. Incident waves in front of the boundary were evaluated using Fourier analysis, and the particles on the transparent boundary were forced to move at the velocity of the analytical solution for Stokes waves in order to absorb the incident waves. The analysis was restricted to periodic waves. Wave propagation was simulated for two wave periods using the developed transparent boundary condition. The results showed that this transparent boundary transmitted the incident waves with small reflection and the simulation cost was lower than that for wave damping by a conventional highly viscous region.     

Study on the Interaction of Water Waves with Semi-Circular Breakwater

—The present study investigates the interaction of steep waves with semi-circular breakwaterwith the complex plane＇s Cauchy boundary integral theorem.The boundary integral method is used totransform the calculation in fluid domain into its boundary alone.In the calculation the computation do-main is moved with the propagation of waves.A numerical solution is obtained for incident Stokes wavespassing the submerged obstacles.This method has been extended to the calculation of wave run-up on aslope for estimating wave overtopping.     

基于类海啸波型的岛礁水动力特性数值模拟研究

基于非静压单相流模型NHWAVE建立了高精度二维数值波浪水槽,采用日本2011年实测真实海啸波型系统研究了海啸波在岛礁上传播变形的规律,并且分析了波高、礁坪淹没水深和礁前斜坡坡度等因素对孤立波和真实海啸传播变形的影响。结果表明,相比孤立波,类海啸波的波长明显大于孤立波波长,在测点处引起的水面变化持续时间更长,同等波高情况下真实海啸波型比孤立波能够携带更多的能量,与岛礁的相互作用也更为复杂,在礁坪上形成的淹没水深约为孤立波的两倍。礁前斜坡坡度和礁坪淹没水深均对类海啸波的反射和透射系数有显著影响。随着礁前斜坡坡度的增加,反射系数和透射系数均逐渐增加。随着礁坪淹没水深的增加,反射系数逐渐减小,而透射系数逐渐增大。但是,反射系数和透射系数均随着入射波高的增加而逐渐减小。     

强非线性和色散性Boussinesq方程数值模型检验

采用同位网格有限差分法,建立了强非线性和色散性Boussinesq方程数值计算模型。以稳恒波Fourier近似解给定入射波边界条件,对均匀水深深水和浅水域不同非线性的行进波、缓坡地形上深水至浅水域的浅水变形波、以及缓坡和陡坡地形上的波浪水槽实验进行了数值计算,并将计算结果与解析解、解析数值解以及实验值进行了较为详细的比较,从而检验了模型的色散性、非线性以及不同底坡下非线性波的浅水变形性能。     

沿岸流不稳定运动传播特性的小波相干谱分析

沿岸流不稳定运动属于超低频运动,研究它的传播特性,有助于深入理解其对岸滩演变、污染物、鱼卵等输移、迁移的影响.本文基于小波相干谱对所选实验波况进行了研究,分析了规则波、随机波入射情况下沿岸流不稳定运动传播特性,并讨论了入射波高、周期、坡度等对其的影响.结果表明,不规则波更易诱导出沿岸流不稳定运动,且在不规则波情况下,不...     

An investigation on internal solitary waves in a two-layer fluid: Propagation and reflection from steep slopes

Experimental investigations on internal solitary wave (ISW) propagation and their reflection from a smooth uniform slope were conducted in a two-layered fluid system with a free surface. A 12-meter-long wave flume was in use which incorporated with: (1) a movable vertical gate for generating ISW; (2) six ultrasonic probes for measuring the fluctuation of an ISW; and (3) a steep uniform slope (from one of θ=30°, 50°, 60°, 90°, 120° and 130°) much greater than those ever published in the literature. This paper presents the wave profile properties of the ISW recorded in the flume and their nonlinear features in comparison with the existing Korteweg de Vries (KdV) and modified Korteweg-de Vries (MKdV) theories. Experimental results show that the KdV theory is suitable for most small-amplituded ISWs and MKdV theory is appropriate for the reflected ISWs from various uniform slopes. In addition, both the amplitude-based reflection coefficient and reflected energy approach a constant value asymptotically when plotted against the slope and the characteristic length ratio, respectively. The reflected wave amplitudes calculated from experimental data agree well with those reported elsewhere. The optimum reflection coefficient is found within the limit of 0.85 for wave amplitude, among the test runs from steep normal slope of 30° to inverse angle of 130°, and around 0.75 for the reflected wave energy, produced by an ISW on a vertical wall.     

NWF: Propagation of Tsunami and its Interaction with Continental Shelf and Vertical Wall

In this article, tsunamis represented as solitary waves was simulated using the fully nonlinear free surface waves based on Finite Element method developed by Sriram et al. (2006). The split up of solitary wave while it propagates over the uneven bottom topography is successfully established. Wave transmission and reflection over a vertical step introduced in the bottom topography is in good agreement with the experimental results from Seabra-Santos et al. (1987). The wave transformation over a continental shelf with different smooth slopes reveals that the solitary wave reflection increases while the continental slope varies from flat to steep. The interaction of the solitary wave with a vertical wall for different wave steepness has been analysed. The reflected shape of the profile is in good agreement with the observation made by Fenton and Rienecker (1982) and an increase in wave celerity is observed.