Analysis of Mixing of Pollutants in Water Waves and Currents

A vertical two-dimensional turbulence numerical model for the interaction of waves and currents is developed in the paper based on the nonlinear two-equation k-ε model with the VOF method.The one-dimensional equivalent advection velocity and equivalent mixing coefficient are defined and the solving process is introduced:The pollutant concentration field,generated by an instant source in waves and currents,is calculated with the model,and then the equivalent advection velocity and equivalent mixing coefficient are obtained by calculating the time derivative of the mean and variance of pollutant concentration probability distribution.The effects of wave period and wave height on the equivalent mixing coefficient for waves and wave-currents are also investigated.     

Numerical Study on Instantaneous Discharge of Unsorted Particle Cloud in Cross Flow

The mixing characteristics of particles such as dredged sediment of variable size discharged into cross flow are studied by a 3D numerical model, which is developed to model the particle-fluid two-phase flow. The Eulerian method with the modified k-ε parameterization of turbulence for the fluid phase is used to solve fluid phase, while a Lagrangian method for the solid phase (particles), both the processes are coupled through the momentum sources. In the model the wake turbulence induced by particles has been included as additional source term in the k-ε model; and the variable drift velocities of the particles are treated efficiently by the Lagrangian method in which the particles are tracked explicitly and the diffusion process is approximated by a random walk model. The hydrodynamic behavior of dumping a cloud of particles is governed by the total buoyancy of the cloud, the drag force on each particle and the velocity of cross-flow. The computed results show a roughly linear relationship between the displacement of the frontal position and the longitudinal width of the particle cloud. The particle size in the cloud and the velocity of cross flow dominate the flow behavior. The computed results are compared with the results of laboratory experiments and satisfactory agreement is obtained.     

Design of ship's bow form by potential-based panel method

A surface panel method treating a boundary-value problem of the Dirichlet type with the free surface is presented to design a three-dimensional body corresponding to a prescribed pressure distribution. The free surface boundary condition is linearized with respect to the oncoming flow, and computed by four-point finite difference scheme. Sample designs for submerged spheroids and Wigley hull are carried out to demonstrate the stable convergence, the effectiveness and the robustness of the method. The design of a 5500TEU container carrier is performed with respect to reduction of the wave resistance. To reduce the wave resistance, calculated pressure on the hull surface is modified to have the lower fluctuation, and is applied as a Dirichlet type dynamic boundary condition on the hull surface. The designed hull form is verified to have the lower wave resistance than the initial one not only by computation but also by experiment.     

A community-wide intercomparison exercise for the determination of dissolved iron in seawater

The first large-scale international intercomparison of analytical methods for the determination of dissolved iron in seawater was carried out between October 2000 and December 2002. The exercise was conducted as a rigorously “blind” comparison of 7 analytical techniques by 24 international laboratories. The comparison was based on a large volume (700 L), filtered surface seawater sample collected from the South Atlantic Ocean (the “IRONAGES” sample), which was acidified, mixed and bottled at sea. Two 1-L sample bottles were sent to each participant. Integrity and blindness were achieved by having the experiment designed and carried out by a small team, and overseen by an independent data manager. Storage, homogeneity and time-series stability experiments conducted over 2.5 years showed that inter-bottle variability of the IRONAGES sample was good (< 7%), although there was a decrease in iron concentration in the bottles over time (0.8–0.5 nM) before a stable value was observed. This raises questions over the suitability of sample acidification and storage.     

Wave-Current Forces on Small Square Cylinders (Part I)

-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.     

A model of the formation and development of ocean shear wave

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确定任意磁性体磁化方向的样条函数法

由磁异常Z_α和重力异常g,利用样条函数的微、积分性质,从泊松方程出发,直接解得磁性体的磁化方向。该方法适用于任意形状磁性体的磁异常。     

Elasto-Plastic Analysis of Tubular Joints of Offshore Platforms by Finite Element Method

The plastic node method is reformulated by the variational principle and is applied to elasto-plastic finite element analysis of tubular joints, eventually including the effect of internal and external gussets, stiffener rings, etc., if necessary. Four different joints are studied here in detail for the elasto-plastic behavior, the strain at the hot spot, the strain concentration factor around the intersection line, and the propagation of the plastic region with loading up to collapse in order to determine the ultimate strength, safety factor, and development of the plastic field. The present results are in good agreement with the experimental results.     

晚第四纪冲绳海槽北段CaCO3含量的时空变化及其控制因素

对取自冲绳海槽北段的6个沉积岩心进行了CaCO3含量、粒度和铀系同位素分析，结合氧同位素数据和海槽其他钻孔的相应结果，探讨了冲绳海槽北部晚第四纪以来CaCO3含量的垂向与横向变化特征。结果表明，冲绳海槽北段沉积总体上表现为全新世CaCO3含量高、晚更新世CaCO3含量低的“大西洋型”碳酸盐演化特征，但冲绳海槽北段和中部的碳酸盐演化特征并不一致，海槽内西坡、槽底和东坡的不同部位其演化特征也存在较大差异。碳酸盐含量的变化与沉积物粒度特征密切相关，晚第四纪冲绳海槽碳酸盐演化的时空差异是多种因素相互作用的结果。     

不同软基处理方法适用性比较

总结分析了国内外现有的软土地基处理的各种方法。通过对采用不同方法进行软基处理的工程实例处理效果的定量对比，发现不同软基处理方法的适用性差异很大，多数工程中仅用一种方法很难达到设计要求，而两种或多种方法联合则可望取得更好的效果。