Fully Nonlinear Boussinesq-Type Equations with Optimized Parameters for Water Wave Propagation

For simulating water wave propagation in coastal areas, various Boussinesq-type equations with improved properties in intermediate or deep water have been presented in the past several decades. How to choose proper Boussinesq-type equations has been a practical problem for engineers. In this paper, approaches of improving the characteristics of the equations, i.e. linear dispersion, shoaling gradient and nonlinearity, are reviewed and the advantages and disadvantages of several different Boussinesq-type equations are compared for the applications of these Boussinesq-type equations in coastal engineering with relatively large sea areas. Then for improving the properties of Boussinesq-type equations, a new set of fully nonlinear Boussinseq-type equations with modified representative velocity are derived, which can be used for better linear dispersion and nonlinearity. Based on the method of minimizing the overall error in different ranges of applications, sets of parameters are determined with optimized linear dispersion, linear shoaling and nonlinearity, respectively. Finally, a test example is given for validating the results of this study. Both results show that the equations with optimized parameters display better characteristics than the ones obtained by matching with padé approximation.     

数值模拟生成畸形波的一种新方法

通过理论分析和数值模拟,结果证明利用Longuet-Hinggins模型可以得到包含畸形波的随机波列,但在组成波的初相位随机分布的条件下,畸形波发生的概率很低且其畸形程度较小。调整组成波的初相位,增加具有相同初相位的组成波个数,可增大畸形波发生的概率,而且所得畸形波的畸形程度也相应增大。将模拟得到的畸形波与实测畸形波进行了比较,发现它们的波形很相似,表明这种模拟方法是可行有效的。     

散乱体数据可视化:海洋水团分析的新途径

应用科学计算可视化技术于海洋学研究在中国尚不多见。本文试图将这一技术引入物理海洋学领域。文中详细介绍了应用散乱体数据可视化划分和分析海洋水团的方法,包括适于水团分析的数据建模,可视化水团及温、盐度场总体分布及特征分布的体绘制法等值面绘制法。最后,给出也这些方法在黄、东海毗邻海区５－６月份水团及温、盐度场分布研究中的实际应用。结论显示了科学计算可视化在海洋学研究中的应用潜力。     

基于相干原理的多波束测深新算法

为了改善多波束声纳的分辨率,提出了一种基于相干原理的测深新算法,对每一个波束脚印内的信号进行相干处理,获得了大量的海底深度值。在此基础上,采用新算法对仿真数据和某型号多波束测深声纳湖上实验数据进行处理。结果表明,相对于传统多波束测深算法,该算法可显著提高声纳海底测量的分辨率,获得大量的海底深度测量值。     

Research on Fatigue invalidation of A Submarine Pipeline Span Subjected to Waves and Currents

1 .IntroductionRecently, more and more importance is attached to the development of offshore oil and gas alloverthe world and many submarine pipelines have been laid.Submarine pipelines are the lifeline ofthe transportation of offshore oil and gas .Submar…     

储层的连通性模拟方法

连通性是储层的基本性质之一,它直接影响着采收率。如果部分储层没有与井连通,那么这部分油藏就不能被有效开采。确定地质体或砂体的连通性可以作为连通储层的百分比率,同时,确定储层连通性也作为与井连通的储层百分比率。先前的研究绝大多数考虑连通性的数学、物理和工程方面,现在的连通性研究则使用地层学的简单三维地质统计模型来表征。这些模型研究显示层状连通性较好,如果净总比或砂岩部分大于30％,其连通状况可以超过90％;当净总比低于30％的时候,连通性就会有1个快速的递减作为净总比的功能之一。     

A Sound Approach to Soft Sediment Resolution

The last few years has seen a surge in research activities directed towards investigating properties and dynamics of young marine, limnic and fluvial sediments. It is by now a well established fact that the sequence of sediments ranging from concentrated benthic suspension over fluid mud to un-consolidated material summarized as liquid sediments (LS), act as carriers for a wide range of pollutants discharged or migrated into waterways. Knowledge of the transport and fate of LS allows determining the transport and fate of adsorbed constituents (e.g., heavy metals, pesticides, PCBs, PAHs). To assess the environmental impact of LS, efforts have to be made to better understand the processes in relation to hydrodynamics and the chemical and physical properties of the layers. Since physical laws limit the resolution and detection power of conventional seismo-acoustic systems in respect of LS, alternative measurement, data analysis and processing approaches have to be found. Adapted acoustic procedures initially developed for shallow water marine environments to extreme shallow water regimes using matched field inversion techniques can reveal geoacoustic parameters including density, compressional wave speed and attenuation as a function of depth and time. The paper outlines the effects of sediment mobility upon the environment followed by a short overview of techniques commonly used to investigate sediments and other freshwater/marine events. The problems faced and limitations of existing systems are briefly outlined. Results obtained with recently developed and refined geoacoustic inversion methods are presented highlighting their potential for long-term study of physical properties and dynamics of LS.     

Nonlinear Analysis of Bidirectional Vortex-Induced Vibration of A Deepwater Steep Wave Riser Subjected to Oblique Currents

China Ocean Engineering - An improved three-dimensional (3D) time-domain couple model is established in this paper to simulate the bidirectional vortex-induced vibration (VIV) of a deepwater steep...     

A Tactical Approach to Environmental Uncertainty and Sensitivity

The issues of acoustic sensitivity to environmental parameters and the uncertainty in performance prediction due to lack of accurate environmental inputs are addressed. Special emphasis is given to the current state of affairs and to the importance of communicating in a simple, robust means the uncertainty to the sonar operator. A multistaged approach to estimating sensitivity, computing acoustic propagation uncertainty due to environmental variability is presented. A heuristic approach to estimating the most sensitive environmental parameters is developed. A measurements-based statistical approach is applied to environmental data taken in the Mediterranean Sea to estimate performance uncertainty due to sound speed and geoacoustics uncertainty     

A Finite-Difference Approach to the Time-Dependent Mild-Slope Equation

A finite-difference approach is used to develop a time-dependent mild-slope equation incorporating the effects of bottom dissipation and nonlinearity.The Euler predictor-corrector method and the three-point finite-difference method with varying spatial steps are adopted to discretize the time derivatives and the two-dimensional horizontal ones,respectively,thus leading both the time and spatial derivatives to the second-order accuracy.The boundary conditions for the present model are treated on the basis of the general conditions for open and fixed boundaries with an arbitrary reflection coefficient and phase shift.Both the linear and nonlinear versions of the numerical model are applied to the wave propagation and transformation over an elliptic shoal on a sloping beach,respectively,and the linear version is applied to the simulation of wave propagation in a fully open rectangular harbor.From comparison of numerical results with theoretical or experimental ones,it is found that they are in reasonable agreement.     

Research on Pressure Tight Sampling Technique of Deep-Sea Shallow Sediment-A New Approach to Gas Hydrate Investigation

1 .IntroductionRecent researches have revealed that the geochemical method is an efficient way to indicate theoccurrence of gas hydrate within marine sediments .Accordingtosediment and pore water samples col-lectedfromODPor DSDPdrill cores ,a series of ge…     

一类全局最优化问题的动态隧道方法

研究了连续变量函数的全局最优化问题 ,给出了动态隧道方法。该动态隧道方法由局部搜索和动态隧道 2个阶段构成。在局部搜索阶段用了动态系统方法。对全局最优化问题的实例进行了数值实验 ,数值结果表明了该方法的稳健性和有效性。     

A Kalman Filter Approach to Realize the Lowest Astronomical Tide Surface

In this paper , we present a novel Kalman filter approach to combine a hydrodynamic model-derived lowest astronomical tide (LAT) surface with tide gauge record-derived LAT values. In the approach, tidal water levels are assimilated into the model. As such, the combination is guided by the model physics. When validating the obtained “Kalman-filtered LAT realization” at all tide gauges, we obtained an overall root-mean-square (RMS) difference of 15.1 cm. At the tide gauges not used in the data assimilation, the RMS is 17.9 cm. We found that the assimilation reduces the overall RMS difference by ～ 31% and ～ 22%, respectively. In the Dutch North Sea and Wadden Sea, the RMS differences are 6.6 and 14.8 cm (all tide gauges), respectively. Furthermore, we address the problem of LAT realization in intertidal waters where LAT is not defined. We propose to replace LAT by pseudo-LAT, which we suggest to realize similarly as LAT except that all water level boundary conditions and assimilated tidal water levels have to be enlarged by a constant value that is removed afterward. Using this approach, we obtained a smooth reference surface for the Dutch Wadden Sea that fits LAT at the North Sea boundary within a few centimeters.     

海洋环境中放射性核素扩散模型

本文介绍用网格模型对海洋环境中放射性核素的扩散进行新的数学探讨，假设模型运移系数是水体运动和间隔空间几何形状的函数，该模型系统与放射学历史无关。     

醒神药物莫达非尼合成方法的改进

本文以 1条简单有效的新路线合成了莫达非尼 ,总收率为 6 1.6 %。首先在 Fe(NO3 ) 3 ·9H2 O催化下以二苯甲醇和巯基乙酸合成二苯甲基巯基乙酸 ,进而进行酰胺化反应 ,生成相应的酰胺化合物在双氧水作用下将硫醚氧化为亚枫得到目标化合物。产物用 IR,NMR确证其结构。     

多岛屿、汊道复杂地形海区流场影响的数值模拟研究

复杂地形海区的潮流场特征及工程对其的影响一直是海洋环境研究中比较关注的问题。本文采和正交曲线网格和动边界结合技术，建立了复杂地形海区大范围、局部加密的二维高精度潮流数值模型，研究分析了工程前后宁波大榭岛LPG码头附近复杂海域大范围潮流场特征和局部特殊地形对其的影响，并从动力机制上进行了讨论。结果表明：地形的挑流作用、水流流路分离和多股水流的潮汐动力不均匀等原因，使海区的潮流场结构变得非常复杂，其重要特征是有众多回流区产生。     

等量纬度展开式的新解法

对地图投影学中经常遇到的等量纬度正反解展开式进行了新的研究。借助M athem atica计算机代数系统强大的数学分析功能,给出了新的正解公式,发现并纠正了前人正解公式中的错误;并且以此为基础,导出了用第一偏心率幂级数形式表示的反解展开式和三种主要的参考椭球下的实用反解计算式。本文研究表明计算机代数系统的应用不但极大地提高了公式推演的效率和准确度,而且反解系数从此可以表示为更简单和更便于记忆的符号形式。     

A New Way to Study Water-Vapor Absorption Coefficient

In the visible spectrum, the atmospheric attenuations to sunlight mainly include aerosol scattering, atmospheric molecule Rayleigh scattering and ozone absorption, while in the near-infrared spectrum （from 650 nm to 1 000 nm）, we must take water-vapor absorption into account. Based on the atmospheric correction theory, using spectrum irradiance data measured by Instantaneous Ground spectrometer, ozone content measured by Microtops Ⅱ ozone monitor, water-vapor content and aerosol optical thickness measured by sun photometer, we give a new way to study water-vapor absorption to sunlight, and the result shows that the main peak values of water-vapor absorption coefficients are 0.025 cm^-1, 0.073 cm^-1, 0.124 cm^-1, 0.090 cm^-1, 0.141 cm^-1 and 0.417 cm^-1, which respectively lie at 692 nm, 725 nm, 761 nm, 818 nm, 912 nm and 937 nm.     

A Holistic Approach to Upwelling and Downwelling along the South-West Coast of India

An attempt has been made to develop a holistic understanding of upwelling and downwelling along the south-west coast of India. The main objective was to elucidate the roles of different forcings involved in the vertical motion along this coast. The south-west coast of India was characterized by upwelling during the south-west monsoon (May to September) and by downwelling during the north-east monsoon and winter (November to February). The average vertical velocity calculated along the south-west coast from the vertical shift of the 26?°C isotherm is 0.57?m/day during upwelling and 0.698?m/day during downwelling. It was concluded that upwelling along the south-west coast of India is driven by offshore Ekman transport due to the alongshore wind, Ekman pumping, horizontal divergence of currents and by the propagation of coastally trapped waves. Whereas downwelling along the coast is driven only by convergence of currents and the propagation of coastally trapped Kelvin waves. Along the west coast of India, the downwelling-favorable Kelvin waves come from the equator and upwelling-favorable waves come from the Gulf of Mannar region.