Time domain simulations of radiation and diffraction by a Rankine panel method

The radiation and the diffraction of a ship with a forward speed are studied by using a time domain Rankine panel method. The free surface conditions are linearized onto an undisturbed free surface based on the double body flow. The linearized body boundary condition is applied on the mean wetted hull surface. The fluid domain boundary is discretized by a collection of quadric panels. The unknown quantities, including the free surface elevation, the normal flux over the free surface and the potential on the fluid domain boundary, are determined at each time step. The numerical results are compared with experimental data and other numerical solutions, showing satisfactory agreements.     

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.     

An iterative Rankine BEM for wave-making analysis of submerged and surface- piercing bodies in finite water depth

A 3-D iterative Rankine Boundary Element Method （BEM） for seakeeping problem in time domain is developed in the framework of linear potential theory. Waves generated by both submerged and surface-piercing bodies moving at a constant forward speed in otherwise calm water, and the resultant steady wave pattern, wave profile and resistance are computed to validate this newly-developed code. A rectangular computational domain moving with the same forward speed as the body is introduced, in which an artificial damping beach is installed at an outer portion of the free surface except the downstream side for satisfying the radiation condition. The velocity potential on the ship hull and the normal velocity on the free surface are obtained directly by solving the boundary integral equation, with the Rankine source used as the kernel function. An iterative time-marching scheme is employed for updating both kinematic and dynamic free surface boundary conditions to stabilize the calculation. Extensive results including the wave patterns, wave profiles and wave resistances for a submerged spheroid and a Wigley hull with forward speed are presented to validate the efficiency of the proposed 3-D time-domain higher-order approach. Finally, the sensitivity of ship-generated waves to the water depth is investigated. Computed results show satisfactory agreement with the corresponding experimental data and other numerical solutions.     

考虑绕射效应的沿堤波浪力波动分析

回顾了波浪绕射的理论基础,提出了等水深单突堤的总波浪力相位差修正公式,结合绕射效应解析解和波压计算方法,探讨了波高和波浪力的沿堤波动.分析结果表明,波高沿堤波动导致波浪力沿堤也呈正弦形式的周期性衰减,这正是蛇行破坏现象的内在原因.当不考虑堤后绕射波影响时,堤头附近水平波浪力最大峰值约为立波时的1.2倍,当考虑堤后绕射波影响时,最大峰值可达1.4倍以上.这表明立波系统只是一种总体平均情况,考虑到波浪力的沿堤波动,工程中应加强局部重点堤段的防护.     

广阳水库主要地质问题分析

平原水库大多地质条件较差、围坝较长,往往存在着渗漏、液化、浸没等工程地质问题,该文以拟建的广阳水库为例,介绍了北方干旱地区平原水库主要地质问题的分析方法,可供类似平原水库勘察设计借鉴和参考。     

船舶兴波问题面元法计算中自由面离散的稳定性分析

本文通过多变量的连续及离散Fourier分析，研究了船舶兴波问题中面元法计算的稳定性，对于计及流体域外奇点分布的自由面面元离散方式建立了满足稳定性要求的准则，给出了以网格弗氏数F△及网格纵横尺度比α为参数的稳定性限界线。     

Radiation and diffraction analysis of a cylindrical body with a moon pool

An analytical solution is presented for the radiation and the diffraction of a cylindrical body with a moon pool floating on the surface of water with a finite depth. The expressions for the potentials are obtained by the method of separation of variables, and the unknown coefficients are determined by the boundary conditions and the matching requirements on the interface. The effects of the moon pool on the hydrodynamic characteristics of the body are investigated. Some peaks are observed on the curves of the added mass and damping coefficients, corresponding to the resonant frequencies of the moon pool. The internal free surface moves like a piston at a certain low resonant frequency.     

Selection of organic Rankine cycle working fluids in the low-temperature waste heat utilization

In the current study, simulations based on the engineering equation solver(EES) software are performed to determine the suitable working fluid for the simple organic Rankine cycle system in different temperature ranges. Under the condition of various temperatures and a constant thermal power of the flue gas, the influence of different organic working fluids on the efficiency of the subcritical organic Rankine cycle power generation system is studied, and its efficiency and other parameters are compared with those of the regenerator system. It is shown that the efficiency of the subcritical organic Rankine cycle system is the best when the parameters of the working fluid in the expander inlet are in the saturation state. And for the organic Rankine cycle, the R245 fa is better than other working fluids and the efficiency of the system reaches up to 10.2% when the flammability, the toxicity, the ozone depletion, the greenhouse effect and other factors of the working fluids are considered. The R601 a working fluid can be used for the high-temperature heat source, however, because of its high flammability, new working fluid should be investigated. Under the same condition, the efficiency of the organic Rankine cycle power generation system with an internal heat exchanger is higher than that of the simple system without the internal heat exchanger, but the efficiency is related to the properties of the working fluid and the temperature of the heat source.     

船舶在波浪中运动的非线性时域数值模拟

为了可靠地模拟高速及大外飘船型在恶劣海况中的运动响应,该文在基于Rankine源的线性时域数值预报方法的基础上,通过在运动方程中添加考虑瞬时湿表面影响的非线性恢复力和入射波力,建立了船舶在波浪中运动的非线性时域数值模拟方法。该方法在数值计算中仍采用线性自由面条件、平均湿表面面元,采用数值海岸技术来满足自由面上的辐射条件。应用本文建立的非线性时域数值模拟方法对高速水面船DTMB5512和大外飘集装箱船Flokstra进行了顶浪状态下的数值模拟研究,数值计算结果表明非线性时域预报方法计算结果较线性方法更接近于试验结果,说明该文方法的有效性。     

北京河长巡查问题时空集聚分析

为了解决北京市河长巡查数据量大、分析效率低等问题,同时更加直观地展示河湖管理保护中存在问题的时空分布规律,依托北京河长智慧移动终端,将抓取的数据经预处理后,通过计算莫兰指数Moran’s I值,并结合核密度估计函数绘制热力图,从时空2个维度对其集聚情况进行分析。结果显示：巡查问题在时空2个维度上均呈现出集聚性,其中Moran’s I值为0.398 5,中心城区为高聚集区,行政交界处为相对密集区域,东北和西南部呈散点分布;同时受天气影响巡查工作具有时间维度聚集。可见,Moran’s I指数和热力图两者结合可以实时、直观、定量地展现巡查问题的集聚特征,有助于探索河湖管理保护的模式及规律,有效提高巡河路线规划和决策水平。     

浅析水利工程预算评审中的问题及对策

财政投资建设项目预算评审处在起步发展阶段,介绍预算评审的内容及方法,通过对某个水利工程项目的预算评审,提出水利工程预算评审目前存在的问题及对策等.     

国内数字流域研究与问题浅析

数字流域是现代水利信息化的重要组成部分,是"数字地球"在流域尺度上的应用。为更好地为流域管理服务,本文从数字流域的基本框架出发,综合分析了国内数字流域基础信息平台、模型模拟平台、应用决策平台的研究状况以及存在的问题。通过对不同流域数字化建设的研究和讨论,旨在为当前流域水利信息化建设提供参考。     

我国水资源安全现状与主要存在问题分析

水资源安全以水资源系统的状态稳定和功能健全为标志.水资源安全状况与水资源自身条件及承载状况、水环境承载状况、水生态安全状况和经济社会的供水保障状况有关.以水资源可利用量衡量水资源开发利用的压力和承载状况,以纳污能力及主要污染物允许入河排放量衡量入河污染物的达标程度,以河道内生态环境用水标准衡量河流下泄水量和入海水量及其满足生态环境用水要求的状况,以先进合理的用水定额衡量区域用水水平与效率.选择控制性指标,对我国现状水资源安全进行综合评价与分析,从而进一步揭示和深层次分析我国水资源问题.     

流体-固体瞬态动力耦合有限元分析研究

本文应用有限元法探讨了流体与固体的瞬态动力耦合分析. 利用拉氏乘子法, 给出了流体与固体接触面上一种接触的约束单元, 将流体与固体动力耦合内力作为基本未知量, 使流体域与固体域有机地联系成一整体, 从而实现了流体-固体动力耦合系统的的统一分析. 文中还推导了流固动力耦合系统的有限元控制方程, 编制了计算程序, 数值计算结果验证了耦合模型的正确性及其较高的计算精度, 并表明固体的变形效应对于流体-固体系统的动力响应是显著的.     

三维横观各向同性土体开挖问题有限层求解

首先探讨了有限层法求解开挖问题的难点，即开挖等效荷载的有限层表达和开挖后刚度矩阵的有限层计算，并在此基础上建立了三维横观各向同性土体开挖问题的有限层求解格式，并编制了相应的计算程序。计算结果同实测值的一致性证实方法了的正确性和有效性。     

代建制中委托代理关系的若干问题分析

代建制是我国在市场经济条件下优化投资工程项目管理的重要举措和新的尝试。代建制中委托方和代理方之间是一种典型的委托代理关系。该文分析了委托代理关系的基本特征,从委托代理关系的角度介绍了代建制的特点,并就完善代建制中委托代理关系的激励约束机制提出了具体建议。     

渗流场反分析的一种新的数学解法

本文提出了渗流场反分析的新解法，建议把水头函数展为台劳级数，并略去高阶项，每次迭代中，只需求解传导矩阵１次，其余都是简单的回代计算，这样计算效率有很大提高，同时还建议利用子结构法，能进一步提高计算效率。     

岳城水库水文遥测系统的应用及存在问题分析

岳城水库水文遥测系统建成运行3年来,对岳城水库乃至海河流域防洪调度提供了重要的依据,产生了巨大的社会和经济效益。目前,在系统运行及管理上还存在一些问题,需要改变管理体制、引进或培养人才来解决。     

波浪绕射非线性数学模型

本文用波数矢量无旋波能守恒方程和非线性弥散关系一起建立了一个浅水波浪绕射的非线性数学模型。在此模型中以非线性弥散关系（经验非线性弥散关系和理论非线性弥散关系）引入浅水波浪绕射理论，组成浅水波浪非线性数学模型。并且在波能守恒方程中考虑了底摩擦的影响。模型中通过对一个斜坡浅滩水域的波浪绕射现象。对使用经验非线性弥散关系和理论非线性弥散关系以及线性弥散关系的计算结果进行了比较。结果表明；使用非线性弥散关系比使用线性弥散关系的计算结果与试验结果现加吻合；水波在浅水传播时使用经验非线性弥散关系和使用理论非线性弥散关系两者相关甚微，但采用经验弥散关系近似波浪在浅水传播时的非线性的计算量远小于理论非线性弥散关系的计算量。所以在实际应用时采用经验非线性弥散关系是较为简单合理的和完全可行的。     

河流泥沙与磷作用情景模拟及分析

泥沙是河流水环境系统的重要组成部分,泥沙运动过程和泥沙吸附解吸作用对河流水质具有显著的影响。天然河流中泥沙运动状态存在一定的变化,尤其是河流上修建大坝蓄水后,库区泥沙运动过程的变化更加明显,相应也会引起水环境条件的改变。本文采用挟沙水流水质一维数学模型,以磷为代表污染物,在一定的水流、泥沙和水质的计算条件下,对泥沙稳定吸附、泥沙淤积、床沙冲刷和不同冲刷位置等4种情景对水环境的影响进行了模拟和分析。通过模拟说明了特定条件下泥沙运动状态和吸附特性变化对水环境的影响,从而为进一步认识天然河流中泥沙对水环境的影响提供支持。