基于连续性扩散流的湿地表面水流动力学模型

受表面密生植被的影响,湿地表面流总是处于高阻力、低流速状态。湿地表面流的水流动力学方程中,其水流加速度项相对于地表高密度植被造成的高阻力项相比,可以忽略。由此,以水流连续性方程和忽略加速度项的水流动力学方程为基础,构建基于连续性扩散流的湿地表面流动力学模型。该模型是一个抛物型偏微分方程,相对于描述一般径流流态的圣维南双曲型偏微分方程组而言,其求解过程相对容易。模型中的表面流流量采用修正的曼宁方程描述,表面糙率采用已有经验公式,数值计算方法采用六点差分格式。模拟结果表明,该模型能够体现湿地表面流的高阻力、低流速特征。水深越浅,水流模式变化越慢,水深越大,表面流受植被阻力越小,水流模式变化越快。     

浅水方程源项处理的研究进展

浅水方程由纳维-斯托克斯方程推导而来,是一种描述具有自由表面的浅水体在重力作用下流动的数学模型。实际浅水流动不可能是完全理想的情况,必须考虑底坡和摩阻等源项的存在,它们影响计算的稳定性和精确性,如果处理不当还会造成格式的不和谐,因此源项处理是求解浅水流动方程的关键,也是国内外学者研究的一个重要方向。介绍目前求解浅水方程存在的4个主要困难,介绍浅水方程的各种离散方法以及优缺点,阐述源项处理的重要性和源项的分类,回顾和总结国内外处理源项的方法以及目前存在的困难。根据目前的研究进展,源项处理依旧有广阔的研究前景,如何平衡好源项处理方法的正效应和负效应是一个值得研究的课题。     

三维无单元伽辽金法及其在拱坝分析中的应用

本文介绍了三维无单元伽辽金法的基本理论，并将其应用于拱坝结构分析中，基于变分原理推导出三维线弹性无单元伽辽金法的整体平衡方程。为了处理实际水利工程中断层、宏观裂纹等不连续情况，采用可视准则处理不连续面对积分点影响域的影响，同时考虑不连续面两表面相互作用对整体平衡方程的贡献。编制了三维无单元法计算程序并用以分析拉西瓦水电工程拱坝一地基系统模型，结果表明，其反映了拱坝在水荷载作用下的位移分布规律。     

一种浅水波浪数值模型的应用研究

简述目前几种浅水波浪数值预报模式，介绍了国内外以能量平衡方程预报浅水波浪的若干模式，重点介绍了应用当今最新波浪研究成果发展起来的并经过若干理论及现场观测资料验证的SWAN模型，详细论述了模型的特点及其适用性，其动谱能量平衡方程的数值离散格式及对能量源汇项的处理方法，利用SWAN模型计算了在不同水深时流场对波浪传播的影响，并与线性波流理论计算结果进行比较；最后，将模型应用于海安湾的浅水波浪数值计算，模拟湾内波高及周期场分布，并与观测结果进行比较。     

非恒定水深平均的K－ε紊流模型的有限元模式

本文在水深平均的二维流动的数学模型基础上，引入Ｋ－ε二方程模式，建立了水深平均的Ｋ－ε紊流模型，采用能适应不规则边界的有限元计算模式，对易引起不稳定的对流项引进迎流技巧，从而大大提高了计算稳定性。针对应用到河口海湾中的紊流模型具有大尺度计算网格的特点，本文分析了常用壁面律的局限性，比较了Ｋ方程中ＧＫ项与ＧＫＶ项的大小，并分析了紊流模型的优点。     

非恒定水深平均的K—ε紊流模型的有限元模式

本文在水深平均的二维流动的数学模型基础上，引入Ｋ－ε二方程模式，建立了水深平均的Ｋ－ε紊流模型，采用能适应不规则边界的有限元计算模式，对易引起不稳定的对流项引起迎流技巧，从而大大提高了计算稳定性，针对应用到河口海湾中的紊流模型具有大尺度计算网格的特点，本文分析了常用壁面规律的局限性，比较了Ｋ方程中Ｇｋ项与Ｇｋ项与Ｇｋｖ项的大小，并分析了紊流模型的优点。     

微气泡降低平板阻力的研究

本文根据计算结果,研究了边界层中的微气泡对平板表面摩擦阻力的影响。建立了含有微气泡的平板边界层方程,并采用一种简单的混合长度模型和有限差分方法对该方程进行了数值计算。分析和讨论了某些参数变化对微气泡降阻的影响。计算结果表明,在一定条件下,湍流边界层的表面摩擦阻力可降低60％左右,其数量级和趋势与国外实验结果相比大体上一致。另外,本文对微气泡降阻机理提出了自己看法。     

Boussinesq方程的二阶椭圆余弦驻波解

等深浅水域中的流体运动可由Boussinesq方程描述.众所周知,该方程有行进波解(孤立波及椭圆余弦波).本文则以Boussinesq方程为控制方程,利用渐近匹配法对椭圆余弦波在直墙上反射进行研究,给出了反射过程中内、外场波形及速度变化的解析表达,从而得到了Boussinesq方程的二阶椭圆余弦驻波型的解析解,并讨论了这类驻波的若干性质.当波长无限增大时,所得解析解收敛于孤立波的情况.这些解析结果不仅有助于揭示岸坡对非线性浅水波影响的力学机理,在海岸防护和开发和岸壁附近结构物的设计条件等工程领域中也具有现实的指导意义.     

长江口盐水入侵数值模型研究

本文利用ECOM模式建立了一个长江口水动力盐度三维数值模型。当水底地形变化比较剧烈时，原ECOM模式中水平扩散项的计算就可能产生虚假的流场和物质输运，所以文中首先对ECOM模式物质输运方程的水平扩散项计算方法进行改进，采用返回z坐标系计算，离散变量利用σ层二次Lagrange插值得到。对于改进方法，文中采用Huang＆spaulding提出的数值试验进行验证，证明此方法大大地提高了水平扩散项的计算精度。改进模型采用长江口实测水文资料进行率定验证，计算和分析了南北槽垂向盐度分布和盐水通量过程，结果表明，模型能较好反映测点盐度变化过程，也能较好地模拟出垂向表底层的盐度差异。     

任意流场中稀疏颗粒运动方程的数值解法及其应用

任意流场中稀疏颗粒运动方程是一非线性的微分积分方程，极难获得解析解。本文首先对方程中Ｂａｓｓｅｔ力项构造了适当的计算格式，然后详细研究了颗粒运动方程的数值计算方法并提出称之为Ｐ（ＥＣ）＾ｋ多步法的差分格式，简要分析了该格式的收敛性和代数精度，给出了时域离散长长必满足的条件。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

Impacts of Microcystis on algal biodiversity and use of new technology to remove Microcystis and dissolved nutrients

Cyanobacteria often dominate eutrophic lakes, outcompeting green algae that are required by fish and zooplankton. This study was undertaken to ascertain the impact of the cyanobacterium, Microcystis, on algal biodiversity. Under laboratory conditions, we found that the presence of Microcystis decreased phyla richness by 58%, phyla evenness by 47%, genera richness by 66% and genera evenness by 51%. Analysis by mixed anova s demonstrated a significant interaction between treatment and time and confirmed a significant reduction in richness and evenness of phyla and genera. We also conducted a phosphate restriction assay on the algae in Mason Lake (Irvine, CA, USA) and found that the threshold needed for algal growth there was 0.02 mg L^?1 PO₄. A pilot study was then conducted to test the effectiveness of the Blue Pro? water treatment facility in removal of this colonial organism from Mason Lake, in addition to removal of dissolved nutrients required for its growth. We measured a 97% reduction in Microcystis cells, a 72% reduction in chlorophyll‐a, and a 96% reduction in phosphate after just one 10 min cycle through the unit. Our study demonstrated that removal of Microcystis colonies may allow green algae to increase in numbers. This may improve algal biodiversity, which will benefit zooplankton and fishes.     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

簸箕李引黄灌区水沙分布及优化调度的经验

灌区利用水沙观测所取得的资料和试验数据，运用水沙运动力学理论，总结分析和揭示了灌区水沙分布的规律和特点。在此基础上，结合灌区的实际运行情况，围绕减少骨干渠道的淤积进行探讨、研究，进而，优化水沙调度方案。该方案实施后，骨干渠道减旅伴效果明显，取得了成功的经验。     

小湾水库大坝防渗面板及其裂缝的加固处理

小湾水库大坝防渗面板整体抗渗性能差,且存在多条裂缝,通过对面板钢丝网喷涂丙乳砂浆加固处理及其裂缝修补,大坝渗漏量明显减少,且左岸上灌浆廊道内及大坝下游坝面92～93 m高程下廊道入口处原有小股射流全部消失.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.