THEORY AND NUMERICAL ANALYSIS OF THE INTERACTION BETWEEN TURBULENCE AND SUSPENDED SEDIMENTs

The coupled hydrodynamical-ecological model for Regional and Shelf Seas Coherens was modified through introducing sediment model in order to simulate suspended sediment transport and account for the interaction between turbulence and sediment. To discuss the effects of sediment on vertical eddy viscosity and diffusion coefficients, the damping function of sediment on turbulence was introduced into one equation k-ε turbulence closure model. Moreover, it is assumed that local equilibrium among turbulence production, dissipation and buoyancy destruction exist near the bottom. The local equilibrium assumption is introduced into the one equation k-ε model and the specific formulation of local equilihrium for one equation k-ε was derived. The tidal current was calculated for Youngkwang Bay near the west coast of Korea. Meanwhile, the suspended sediment was also simulated with the local equilibrium assumption and damping function of sediment on turbulence. It is found that the damping function of sediment reduces vertical eddy viscosity and diffusion coefficients. The local equilibrium assumption changes obviously bottom layer turhulence intensity and sediment concentration.     

EVALUATING THE ROBUSTNESS OF FACTS-BASED STABILIZERS AND PSSS BY DAMPING TORQUE ANALYSIS IN MULTI-MACHINE POWER SYSTEMS

In this paper, the damping torque analysis is applied in a multimachine power system installed with FACTSbased stabilizers and PSSs, which leads to the establishment of a multichannel model describing the pattern of the stabilizers to provide damping to the oscillation modes in the power system. Based on the model, an index is proposed to evaluate the robustness of the stabilizers to the variations of system operating conditions. One application of the index proposed is demonstrated to select the operating condition of the power system, at which the stabilizers are designed to ensure their robustness. This demonstration also reveals the inherent disadvantage of simultaneous tuning techniques for the coordinated design of multiple stabilizers in multi-machine power systems.     

Theoretical and numerical investigations of wave resonance between two floating bodies in close proximity

A simple theoretical dynamic model with a linearized damping coefficient is proposed for the gap resonance problem, as often referred to as the piston mode wave motion in a narrow gap formed by floating bodies. The relationship among the resonant response amplitude and frequency, the reflection and transmission coefficients, the gap width, and the damping coefficient is obtained. A quantitative link between the damping coefficient of the theoretical dynamic model(ε) and that devised for the modified potential flow model(μ_p) is established, namely, μ_p=3πεω_n/8 (where ω_n is the natural frequency). This link clarifies the physical meaning of the damping term introduced into the modified potential flow model. A new explicit approach to determine the damping coefficient for the modified potential model is proposed, without resorting to numerically tuning the damping coefficient by trial and error tests. The effects of the body breadth ratio on the characteristics of the gap resonance are numerically investigated by using both the modified potential flow model and the viscous RNG turbulent model. It is found that the body breadth ratio has a significant nonlinear influence on the resonant wave amplitude and the resonant frequency. With the modified potential flow model with the explicit damping coefficient, reasonable predictions are made in good agreement with the numerical solutions of the viscous fluid model.     

HYDRODYNAMIC CHARACTERISTICS AND SEISMIC ANALYSIS OF OFFSHORE CYLINDRICAL STRUCTURE-FLUID-SOIL SYSTEMS

An analytical method is developed to solve the coupled vibration problem of a vertical elastic circular cylindri-cal structure founded on homogeneous elastic soil with surrounding fluid. An improved mathematical model isadopted by which not only the structure-fluid interaction but also the influence of soil are considered. The frequen-cy-dependent radiation added mass and hydrodynamic radiation damping are expressed in closed form, and arecompared with generalized mass and damping respectively. Their variations with the exciting frequency are studiedas well. A discussion of the influences of structure fluid interaction and structure-soil interaction upon hydrody-namic loading is given.     

STABILITY ANALYSIS OF COUPLED SYSTEM OF MAGNETIC HEAD AND ULTRA-THIN GAS FILM

This paper presents a pressure perturbation equation for the ultra-thin gas film lubrication of magnetic head-disk based on a generalized gas lubrication equation applicable to arbitrary Knudsen number. The gas film pressure of Air Bearing Slider (ABS) was obtained by using the operator-splitting and finite element method. The pressure perturbation equation was solved by the finite element method wit hunstructured triangle grids to calculate the stiffness and damping coefficients of the gas film. Modal analysis of coupled systern of magnetic head and gas film was carried out to obtain natural frequencies, damping rates and mode shapes of the magnetic head vibrations. Vibration stability of Ω-type magnetic head was predicted in this work. Numerical results indicate that the natural frequencies of the coupled system increases as the gas film thickness decreases, and the natural frequencies and damping rate of the coupled vibration modes of heave and piteh motions are much lower than those of uncoupled modes. And it is concluded that the stability of magnetic head is slightly worsened when the disk rotation speed increases.     

THE STRUCTURE AND SCALE EFFECT OF WALL TURBULENT FLOW

In this paper the structure and scale effect of wall turbulence are investigated.Thecharacteristics of the turbulence structure in the wall region is described.The fact that the turbu-lence in whole flow field is controlled mainly by the structure of wall turbulence is demonstrat-ed.Discussion is concentrated on the scale effects of the streak structure,the vortex structureand the bursting frequency.     

THE RADIATION AND DIFFRACTION OF WATER WAVES BY A BOTTOM-MOUNTED CIRCULAR CYLINDER IN A TWO-LAYER FLUID

An analytical method was proposed to analyze the radiation and diffraction of water waves by a bottom-mounted circular cylinder in a two-layer fluid. Analytical expressions for added mass and damping coefficients, as well as the wave excitation forces of the circular cylinder were obtained by an eigenfunction expansion method. The hydrodynamic forces on the bottom-mounted circular cylinder in a two-layer fluid include not only the added mass and damping coefficients, but also the wave forces of the surface and internal-wave modes. This is different from the case of a homogenous fluid. Some examples were given, showing that density stratification can have a relative large effect on these hydrodynamic forces over a wide range of frequencies.     

OBSERVATION AND ANALYSIS ON CHARACTERISTIC OF NATURAL RIVERS

Based on the previous study on turbulent structure, field experiments on fluctuation velocity were carried out in section Huanglingmiao of main stream of Yangtze River with a 3-D Doppler velocimeter. And a number of data such as velocity of different discharge and different vertical line were obtained. According to the field experiment data, period, frequency, period function and probability density function of large-scale coherent structure in natural river were prescribed by means of quantitative analysis. And the problem about distribution of time average velocity, turbulent intensity and Reynolds stress along depth were further analyzed and calculated. The results in this paper will deepen the understand of large-scale turbulent structure in natural river and so make the base for applying“turbulence theory” to water conservancy, hydroelectric, environment engineering and so on.     

An iterative Rankine boundary element method for wave diffraction of a ship with forward speed

A 3-D time-domain seakeeping analysis tool has been newly developed by using a higher-order boundary element method with the Rankine source as the kernel function. An iterative time-marching scheme for updating both kinematic and dynamic free-surface boundary conditions is adopted for achieving numerical accuracy and stability. A rectangular computational domain moving with the mean speed of ship is introduced. A damping beach at the outer portion of the truncated free surface is installed for satisfying the radiation condition. After numerical convergence checked, the diffraction unsteady problem of a Wigley hull traveling with a constant forward speed in waves is studied. Extensive results including wave exciting forces, wave patterns and pressure distributions on the hull are presented to validate the efficiency and accuracy of the proposed 3-D time-domain iterative Rankine BEM approach. Computed results are compared to be in good agreement with the corresponding experimental data and other published numerical solutions.     

A NEW DEPTH-AVERAGED TWO-EQUATION (K-) TURBULENT CLOSURE MODEL AND ITS APPLICATION TO NUMERICAL SIMULATION FOR A RIVER

The paper mainly focuses on describing the modification made to a new depth-averaged two-equation turbulent closure model based on the revised κ-ω model recently. In the case of side discharged jets with tempera-ture difference and transverse current, the new model has been investigated numerically in detail. As a practicalexample of application to use the new model, the side discharge of the cooling water from three outlets into a natu-ral river on one bank has been simulated, and the geomorphic variation under water has been treated suitably. Twodepth-averaged models, and have been used, the later was the unique one up to the present. Emphasisis placed on the comparative research with different models under the same computational conditions. It has beenverified that if the discharged flow rates are relatively small, when the pollutant plume in the near and transitionalzons is predicted, the agreement with experimental and field data simulated by the model is better than by the model or other methods commonly used in engineering.     

水土保持与环境保护

简述了水土保持与环境的关系，指出水土保持是环境保护的重要手段。     

水闸破坏症状与除险加固措施简述

本文针对水闸破坏症状，结合漳州市及国内水闸情况，总结除险加固的各种实用技术，对类似工程的除险加固具有广泛的适应性。     

浅谈水利水电行业勘测设计工作的经营及管理

阐述了水利水电行业勘测设计经营工作，及其经营管理的关键因素，供同仁借鉴。     

水土保持与防洪减灾浅议

我国是世界上洪水灾害最严重的国家之一，洪水造成的经济损失和人员的伤亡，在各种自然灾害中居第一位，严重影响社会的安定与国家盛衰，通过分析洪水成灾因素，指出水土流失是造成洪水灾害的重要原因，而水土保持是防洪减灾的根本措施，并对未来水土保持防洪减灾提出了几点建议。     

大坝裂缝及接缝监测设计与监测方法

大坝裂缝及接缝监测对于了解坝的工作性态和整体性，分析其产生的原因和对大坝安全的影响，以便必要时进行有效的处理都是非常重要的。文章对与此有关的技术问题进行了探讨。     

江西省2005年暴雨洪水特性及水文测报工作

对江西省2005年暴雨洪水特性进行了分析,并对防汛水文测报工作和水文防御山洪地质灾害的经验做了总结.     

浅淡溢洪道改扩建方案与选择

溢洪道改扩建和进行溢洪道方案布置，要择优选取溢洪道进口型式、防冲消能工，以使其工程量省、施工快、运行管理方便     

水工建筑物老化和维修及后评价

水利工程及其建筑物老化和维修问题日益突出，引起人们的关注，通过水工建筑物的老化进程分析，进行了维修加固与结合安全度之间关系研究，并对水工建筑物的后评价问题进行了讨论。     

水土流失对樟树市江河防汛抗旱的危害与防治对策

介绍了水土流失对樟树市江河防汛抗旱的危害及相应的防治对策．     

鄱阳湖蓄滞洪与湿地保护

根据鄱阳湖分洪量变化情况和湿地状况，对鄱阳湖分蓄洪区与湿地保护关系和自然保护对湿地的要求等进行了分析论述．