THE STATISTIC CHARACTERISTICS OF IRREGULAR BREAKING WAVE FORCES ON VERTICAL WALLS

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Extreme wave loads on submerged water intakes in shallow water

This paper provides new guidance concerning the hydrodynamic loads on submerged intake structures located in shallow water under breaking and non-breaking waves. Results from a series of experiments conducted in a large wave flume at 1:15 scale to study the hydrodynamic forces exerted on a generic intake structure located on a sloping seabed in shallow water below breaking and non-breaking irregular waves are presented. Based on analysis of the experimental data, empirical relationships are developed to describe the peak loads in terms of characteristic wave parameters such as significant wave height and peak wave period. The distribution of the peak loads across different parts of the intake structure is also described. Drag and inertia force coefficients for the horizontal forcing on the intake structure and for the main structural sub-components are derived and presented. It is shown that the well-known Morison equation, with appropriate drag and inertia force coefficients, can provide reasonable estimates of the moderate horizontal loads, but the peak loads are less well predicted.     

面流消能下游水面波动的统计特性：面流消能试验研究之三

论述了面流消能下游旋滚后水面波动的统计特性。分析表明，波面振幅的概率密度基本符合正态分布，平均波高的概率密度接近瑞利分布。对旋滚后的波动传递速度与波长也作了初步探讨。     

瑞利阻尼参数对瑞利波作用下场地动力响应的影响

为研究地震中Rayleigh波对地表浅层土体的响应特征,针对Lamb问题的模型工况开展有限元动力分析,验证有限元法精确模拟Rayleigh波作用效应的可行性。以厦门地区浅层的素填土及粉质黏土为研究对象,采用摩尔-库仑本构模型,结合Rayleigh阻尼,并在模型的底部和边界上采用黏性边界,采用有限元法考察Rayleigh阻尼中质量比例阻尼系数α和刚度比例阻尼系数β对响应特征的影响规律。研究表明:有限元动力分析可以模拟Rayleigh波作用下的远场动力问题,能取得与Lamb问题解析解较为一致的解答,同时还可以捕捉P波和S波的到达时间;α的变化对素填土和粉质黏土中Rayleigh波的传播特征基本没有影响;β的变化不会影响传播速度,但影响波的振幅,β是Rayleigh阻尼的主控参数。该结论可为采用有限元法研究Rayleigh波对浅埋结构物的地震动力响应提供理论基础和科学依据。     

不同边界条件下非饱和土地基中的Rayleigh波传播

地球表面绝大部分土层并非处于完全饱和状态,故采用传统的饱和土两相介质理论进行动力学分析时,计算结果往往与实际情况不符。针对这一客观问题,以非饱和土为研究对象,在三相孔隙介质波动理论的基础上开展了非饱和土体半空间中Rayleigh波的弥散特性研究。分别考虑了两种不同的边界条件:(a)不透水不透气地基边界;(b)透水透气地基边界。根据边界条件及相关的本构关系式,推导出相应Rayleigh波的弥散方程,再通过Newton-Raphson法进行数值求解。最后讨论了在不同边界条件下,非饱和土地基表面附近Rayleigh波的弥散特性受到地基土饱和度、频率以及土体固有渗透系数的影响。计算结果表明:在两种边界条件下Rayleigh波的传播均受到地基土饱和度变化的影响。并且,频率及渗透系数在不同边界条件下对Rayleigh波特性的影响明显不同。     

浅水波的位移法求解

浅水波的速度分布与水深无关，位移也与水深无关，相当于杆件的刚性横截面假定。文中采用物质坐标，用水平位移作为基本未知量，将浅水波分析按固体力学中杆件非线性大位移问题处理。于是，分析力学的变分原理都可运用了。可采用正则变换，近似解的保辛积分等有效手段进行数值求解。以三峡升船机船厢中水波为例的计算，说明所论方法的有效性。     

椭圆余弦波对V形防波堤绕射波浪力的解析计算

应用椭圆余弦波理论,给出了V形薄壁防波堤的浅水波绕射理论解,对现有Airy微幅波理论进行了有效拓展。通过对V形防波堤的浅水波浪力进行试算,揭示了椭圆余弦波对防波堤的作用规律。计算结果表明:椭圆余弦波理论计算的V形防波堤的最大无量纲波浪力明显大于相同浅水条件下Airy微幅波理论的对应结果,该方法有效拓展了无限长直立薄壁堤的反射波理论。此外,浅水波入射角、V形堤张角和防波堤臂长与水深比等参数的变化均将对V形堤的波浪作用产生相关影响,而V形堤的实际绕射波浪力幅值将随浅水波特征参数值的增大而增大。     

饱和土层中瑞利波的传播特性

本文基于Biot提出的饱和多孔介质的弹性波动方程，导出饱和土层中瑞利波弥散特征方程，并由此分析了瑞利波的弥散特性和位移分布规律。结果表明，饱和土(有渗流)的瑞利波弥散曲线与饱和封闭系统(无渗流)相差很小，可利用饱和封闭系统情况来研究和分析饱和土中瑞利波特征以及现场所测瑞利波弥散曲线。饱和土层中瑞利波的有效传播深度约为1.5倍波长。     

Non-hydrostatic versus hydrostatic modelings of free surface flows

The hydrodynamics of geophysical flows in oceanic shelves, estuaries, and rivers are often studied by solving shallow water equations under either hydrostatic or non-hydrostatic assumptions. Although the hydrostatic models are quite accurate and cost-efficient for many practical applications, there are situations when the fully hydrodynamic models are preferred despite a larger cost for computations. The present numerical model is implemented by the finite volume method (FVM) based on unstructured grids. The model can be efficiently switched between hydrostatic and non-hydrostatic modules. The case study shows that for waves pro-pagating along the bar a criterion with respect to the shallowness alone, the ratio between the depth and the wave length, is insufficient to warrant the performance of shallow flow equations with a hydrostatic approach and the nonlinearity in wave dynamics can be better accounted with a hydrodynamic approach. Besides the prediction of the flows over complex bathymetries, for instance, over asymmetrical dunes, by a hydrodynamic approach is shown to be superior in accuracy to the hydrostatic simulation.     

浅水波与圆弧型贯底式防波堤的相互作用

该文基于椭圆余弦波绕射理论,应用特征函数展开法,推导了浅水波对圆弧型贯底式多孔介质防波堤绕射的波势解,并据此解析计算了作用于防波堤的水平波浪载荷与浅水波波面分布。计算结果表明:浅水波入射角与非线性影响参数、海况条件以及防波堤几何条件等因素的相对变化对波浪作用均存在一定的影响,结构透空可以明显减弱防波堤所受波浪作用。与微幅波理论对比可知:在一定浅水条件下采用椭圆余弦波一阶分量模型所计算的最大无量纲波浪力、力矩和波面分布值均明显高于微幅波理论的对应估值,反映了水波非线性因素的影响效应。     

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。     

NUMERICAL STUDY OF SQUARE-STERN SHIP WAVE IN SHALLOW WATER

This paper employed shallow water equations with moving pressure to calculate water waves generated by a square-stern ship in shallow water. The moving ship is considered as moving pressure on free surface. The finite element method with moving grids is used to solve the shallow water equations based on wave equation model [3]. A non-reflection boundary condition [5]is imposed on open boundaries surrounding the ship. 3-D surface elevations, depth-averaged horizontal velocities are presented. The numerical solutions are physically reasonable. It is found that wave resistance coefficients, draftchange and pitch angle vary rapidly in neighborhood of critical flow (Fh=u/ gh= 0. 9 -1. 1). The numerical results also indicate that the wave resistance coefficients, draft change and pitch angle of square-stern ship are larger than those of sharp-stern ship with the same hull structure at the same speed.     

太湖长兜港固体悬浮物再悬浮的室内模拟

定量研究浅水湖泊动力扰动与沉积物再悬浮的关系,目前仍是湖泊研究中的难点之一。实验利用再悬浮发生装置,对太湖长兜港沉积物风浪扰动进行室内模拟,建立扰动强度与有效波高之间的关系,定量分析风浪对太湖水体中悬浮物的影响及固体悬浮物在水体中的垂向分布,初步得出风浪对太湖沉积物扰动深度一般在毫米级的结论。     

基于SWASH模型的近岸波浪传播变形数值模拟

SWASH模型是一种新型的非静压时域波浪模拟。为了探讨SWASH模型对于解决近岸波浪传播变形问题的适用性,在对其控制方程、边界条件、数值解法等进行介绍的基础上,采用该模型分别模拟了正向规则波、斜向规则波和斜向不规则波入射条件下L形防波堤附近水域的波浪场和波生流场,并与物理试验结果进行对比。结果表明,SWASH模型较好地复演了波浪在近岸区域所发生的浅水变形、折射、破碎,以及堤前反射、堤内绕射等物理现象,波高沿断面的定量分布与试验结果吻合良好,同时较好地模拟了不同波况下防波堤附近水域的波生流场,说明该模型适用于复杂岸线和地形条件下波浪传播变形的数值模拟。     

NUMERICAL MODELING OF WAVE EVOLUTION AND RUNUP IN SHALLOW WATER

Based on the Navier-Stokes (N-S) equations for viscous, incompressible fluid and the VOF method, 2-D and 3-D Numerical Wave Tanks (NWT) for nonlinear shallow water waves are built. The dynamic mesh technique is applied, which can save computational resources dramatically for the simulation of solitary wave propagating at a constant depth. Higher order approximation for cnoidal wave is employed to generate high quality waves. Shoaling and breaking of solitary waves over different slopes are simulated and analyzed systematically. Wave runup on structures is also investigated. The results agree very well with experimental data or analytical solutions.     

二层流体浅水波演化模型

本文在Boussinesq的浅水波假定下，采用各层内任意点ziα速度水平分量代替传统的垂向平均速度，推导出了各层速度的三个分量及压力由各层内点ziα速度水平分量表示的沿垂向分布，将三维问题简化为二维问题，建立了二层流体浅水波演化模型，即二层流体的改进Boussinesq方程组。在该方程组中，随ziα距交界面距离不同，该二层流体浅水波演化模型具有不同的色散特性和非线性。作者证明文中参数αi皆取-0.393时，该方程组具有最佳的色散特性。该方程组不仅适于模拟波浪沿水平方向从深水域向浅水域传播时的折射、绕射和反射问题，而且也适用于研究在浅水或中等水深的水域中波浪传播问题。     

随机波浪作用于三桩桩列上的横向力的水动力特征及群桩效应

本文试验研究了随机波浪作用于串列及并列三桩桩列上的横向力的水动力特征及组成桩间的群桩效应，给出了横向力系数与ＫＣ、ＬＤ两参数的相关曲线。在频域内建议了一个新参数一横向力比频率，它能从一个方面较好地概括横向力谱的特征。以孤立桩柱的横向力为基准考查了桩间相互干扰产生的横向力变化，并以群桩横向力系数描述了这一变化规律。针对随机波浪的特点，文中给出了计算各组成桩上横向力及合力的实用化方法。     

WAVE EQUATION MODEL FOR SHIP WAVES IN BOUNDED SHALLOW WATER

1.　 INTRODUCTIONIn the recentyears,waves in coastal shallow water,generated by marine traffic and in-tensified by port expansion,interaction with structures and reflection of land boundaries,has become a crucial factor affecting waterenvironmentsand engineering operation.In com-parison with the wind waves and ocean swells,waves inside harbor exhibitanomalous waveheight in certain areas.The dominantship waves are hardly dissipated in the harbor due tothe interaction with shorelines,and may…     

双局部行进波对流的时空结构

本文通过二维流体力学基本方程的数值模拟，探讨了均匀行进波状态时的阴影强度分布特性。两个Rayleigh数的局部行进波形成过程的计算比较说明局部行进波的稳定性依赖于Rayleigh数的大小。在稳定区间内局部行进波的宽度随Rayleigh数的增加而增加。最后对一个时间周期上行进波场进行平均后说明，场的平均值可以很好的表征双局部行进波特性。     

风浪对浅水湖泊水质的影响机制

以太湖重要的浅水湖湾——东太湖为例,应用经典风浪经验公式,将风速转化为浪高,以直接体现风浪强度,在分析其与污染底泥卷起、水质指标相关关系的基础上,对风浪影响湖区水质的机制进行进一步探究。结果表明:随着风速、浪高的增加,水体浑浊度增加,偏北风作用下湖区浑浊度更高;DO的质量浓度呈降低趋势,全年浓度呈现冬季偏高而夏季偏低的规律;COD的质量浓度呈增加趋势,全年浓度呈现冬季偏高而夏季偏低的规律;TN的质量浓度与风速相关关系不明显,全年浓度呈现夏季偏高而冬季偏低的规律;浑浊度与COD存在较好的相关性。确定风浪对湖区水质的影响机制,旨在为针对性地制定湖泊水质改善措施提供技术支撑。