Hyperbolic Mild Slope Equations with Inclusion of Amplitude Dispersion Effect： Regular Waves

A new form of hyperbolic mild slope equations is derived with the inclusion of the amphtude dispersion of nonlinear waves. The effects of including the amplitude dispersion effect on the wave propagation are discussed. Wave breaking mechanism is incorporated into the present model to apply the new equations to surf zone. The equations are solved nu- merically for regular wave propagation over a shoal and in surf zone, and a comparison is made against measurements. It is found that the inclusion of the amplitude dispersion can also improve model＇ s performance on prediction of wave heights around breaking point for the wave motions in surf zone.     

重力式网箱数值模拟时波浪理论选择

针对重力式网箱数值模拟中波浪理论选择问题进行了专门的分析与讨论。在数值模型中分别采用线性波浪理论和斯托克斯五阶波浪理论,对重力式网箱的主要部件浮架系统和网衣系统进行模拟。通过将模拟结果与试验结果比较分析选取两种不同波浪理论对模拟结果的影响。分析结果认为在相对水深大于0.18情况下,应用线性波浪理论基本可以准确地模拟重力式网箱波浪作用下的运动和受力。     

参数方程法确定线路放样中边桩坐标

给出了线路放样过程中确定中边桩坐标的新方法。根据曲线模型,找出线路控制坐标系与局部坐标系坐标之间的参数方程关系,推出了缓和曲线及圆曲线中、边桩坐标的参数方程,代入已知量求得参数的值,且给出了求解步骤。该方法思路清晰,具有一次转换计算就可以实现获取线路中边桩测量坐标的优点,便于工程应用。     

Mapping of an approximate neutral density surface with Ungridded data

A neutral density surface is a logical study frame for water-mass mixing since water parcels spread along such a surface without doing work against buoyancy restoring force. Mesoscale eddies are believed to stir and subsequently mix predominantly along such surfaces. Because of the nonlinear nature of the equation of state of seawater, the process of accurately mapping a neutral density surface necessarily involves lateral computation from one conductivity, temperature and depth （CTD） cast to the next in a logical sequence. By contrast, the depth of a potential density surface on any CTD cast is found solely from the data on this cast. The lateral calculation procedure causes a significant inconvenience. In a previous paper by present author published in this journal （You, 2006）, the mapping of neutral density surfaces with regularly gridded data such as Levitus data has been introduced. In this note, I present a new method to find the depth of a neutral density surface from a cast without having to specify an integration path in space. An appropriate reference point is required that is on the neutral density surface and thereafter the neutral density surface can be determined by using the CTD casts in any order. This method is only approximate and the likely errors can be estimated by plotting a scatter diagram of all the pressures and potential temperatures on the neutral density surfaces. The method assumes that the variations of potential temperature and pressure （with respect to the values at the reference point） on the neutral density surface are proportional It is important to select the most appropriate reference point in order to approximately satisfy this assumption, and in practice this is found by inspecting the θ-p plot of data on the surface. This may require that the algorithm be used twice. When the straight lines on the θ-p plot, drawn from the reference point to other points on the neutral density surface, enclose an area that is external to the cluster of θ-p points of the neutral density surface, errors will occur, and these errors can be quantified from this diagram. Examples showing the use of the method are presented for each of the world＇s main oceans.     

Shear effects in shakedown analysis of offshore structures

In this paper, a formulation for shakedown analysis of elastic-plastic offshore structures under cyclic wave loading is presented. In this formulation, a fast numerical solution method is used, suitable for the Finite Element Method (FEM) analysis of large offshore structures on which shear effects in addition to bending and axial effects are taken into account. The Morison equation is adopted for converting the velocity and acceleration terms into resultant forces and it is extended to consider arbitrary orientations of the structural members. The theoretical methods of the shakedown analysis are discussed in detail and the formulation is applied to an offshore structure to verify the concept employed and its analytical capabilities.     

用地震定位的方法研究1999年9月21日台湾省集集地震的破裂过程

综合分析了福建数字地震台网的记录特征,认为台湾省集集地震具有多重破裂的特征.根据Pn震相的走时方程构造出双曲线方程组,利用福建台网记录到的Pn波段震相的到时资料,测定了9.21台湾省集集地震8个破裂点的震中位置.结果表明,集集地震的最初破裂点位于23.94°N,120.77°E;接着破裂向初始破裂点的南北两侧扩展,且北侧的振幅大,整个过程至少持续了20 s;这8个破裂点的位置几乎成一直线排列,其方向与该区地块的运动方向相近.     

内孤立波的研究与数值模型

海洋内孤立波是一种特殊的内波,它能够长距离的传播而保持波形的基本不变。世界上很多海域都观测到了内孤立波的存在,我国南海也是内孤立波频发的典型海区。本文介绍了内孤立波的生成机制、南海内孤立波的研究现状并探讨了南海内波的源、最后介绍研究内孤立波所用的传播模型,认为建立水平二维的内孤立波传播模型具有重要的意义。     

海雾生成过程中平流、湍流和辐射效应的数值试验

利用相对湿度方程,结合数值模式研究了在海雾生成过程中平流、湍流和辐射的效应。结果表明,海雾生成的主要“推动力”是长波辐射冷却,湍流冷却在低层主要发生在平流的初始阶段。随着时间的推移,湍流对低层大气很快变为起加热作用,不利于海雾的生成。湍流和辐射效应在低层大气中符号相反(仅在海雾生成的初始阶段符号相同),量级相同,在高层大气中湍流和辐射效应符号相同,但辐射效应占优势。湍流效应和辐射效应是影响海雾生成的主要因素,平流直接作用似乎不大。平流、湍流和辐射效应及其总效应均随时间推移而减小。另外,还初步研究了风速大小和海温高低对平流、湍流和辐射效应及海雾生成的影响。     

Nonlinear Dispersion Relation in Wave Transformation

1 .Ｉｎｔｒｏｄｕｃｔｉｏｎ1ＴｈｉｓｗｏｒｋｗａｓｆｉｎａｎｃｉａｌｌｙｓｕｐｐｏｒｔｅｄｂｙｔｈｅＮａｔｕｒａｌＳｃｉｅｎｃｅＦｏｕｎｄａｔｉｏｎｏｆＣｈｉｎａ (ＧｒａｎｔＮｏ .4 0 0 760 2 6ａｎｄ 4 0 0 760 2 8) Ｃｏｒｒｅｓｐｏｎｄｉｎｇａｕｔｈｏｒ.Ｅ ｍａｉｌ:ｒｊｌｉ@ｈｈｕ .ｅｄｕ .ｃｎ　　Ｉｔｉｓａｖｅｒｙｕｓｅｆｕｌａｎｄｅｆｆｅｃｔｉｖｅｗａｙｔｏａｄｊｕｓｔｔｈｅｗａｖｅｄｉｓｐｅｒｓｉｏｎｒｅｌａｔｉｏｎｆｏｒｔｈｅｓｔｕｄｙｏｆｔｈｅｎｏｎ ｌｉｎｅａｒｉｔｙｏｆｗａｖｅｐｒｏ…     

烷烃与海水界面张力的研究

于１９９１年３月－１９９２年６月间用滴体积法较系统地测定正已烷、正庚烷、正辛烷、异辛烷、正十二烷、正十六烷和煤油与海水在不同的温度（１６－４０℃）和盐度（１０－４０）范围内的界面张力，测定值的相对误差≤０．５％。对数据进行统计处理后，归纳出所研究烷烃－海水界面张力与温度和盐度的经验关系式，计算与实验值相对误差≤０．５％。