基于有限体积法的二维浅水流动数值模拟程序开发

应用近年来浅水动力学理论的研究成果,参考国内外在软件设计方面几十年积累的经验,开发了基于有限体积法的二维浅水流动数值模拟程序CFD-FVM2D.程序以Roe格式的近似Riemann解为基础,离散浅水方程并将源项按特征方向进行特征分解,建立带源项浅水方程的通量平衡的Godunov求解格式,并对摩擦源项采用隐式、半隐式求解格式,以解决浅水方程的间断、动边界和河床起伏问题.     

不平水底浅水波问题的位移法

该文研究考虑不平水底的二维浅水波问题的位移法。利用水平位移与竖向坐标无关的假定,建立了基于位移的浅水波方程和相应的Hamilton变分原理。针对文中提出的基于位移的浅水波方程,利用有限元和保辛算法建立了相应的计算格式。最后给出一个具有抛物线型河床的浅水周期晃荡算例。数值算例表明该方法可以有效模拟带动边界和不平水底浅水波问题。     

二维浅水方程的高阶松弛格式求解

利用松弛方法，将二维浅水方程转化为松弛方程组，并用逐维五阶WENO重构和显隐式Runge-Kutta方法对松弛方程组的空间和时间方向进行离散，建立了求解二维浅水方程的五阶松弛格式。WENO重构方法的引入既提高了格式的精度，又可保证格式是无振荡的。应用该格式对圆柱溃坝等问题进行了数值模拟，计算结果与用其它方法所得结果吻合，表明了方法的有效性。     

基于WENO-Z重构的Osher-Solomon格式求解浅水波方程

浅水波方程在水利、海洋和环境工程中有着非常重要的应用。该文提出一种求解浅水波方程的高分辨算法,对单元交界面处守恒变量进行三阶WENO-Z重构。空间方向上采用三阶WENO-Z重构的Osher-Solomon数值通量,时间方向上采用三阶强稳定的Runge-Kutta方法,将新格式应用于一维和二维不同初值问题的浅水波方程数值求解中,并分析与比较了研究格式的分辨率。数值结果表明:与原格式相比,三阶WENO-Z重构的Osher-Solomon格式分辨率更高。     

非结构化网格下求解二维浅水方程的和谐Roe格式

为保证底坡源项和重力梯度项的平衡离散,采用把底坡源项分解为两不同部分单独处理的方法,在非结构化网格上建立了求解带复杂地形的二维浅水方程数值模型.采用Roe格式的计算界面通量,隐式求解摩擦力源项以增加格式的稳定性,并给出计算格式在非结构化网格上满足和谐性条件的证明.通过实例验证了此格式是和谐的,并具有良好的间断捕捉能力和稳定性.     

大型浅水湖泊风生流场的数值模拟研究

针对大型浅水湖泊水平尺度远大于垂向尺度,水力参数在垂直方向变化要小于水平方向变化,符合浅水流动的特点,采用水深平均的紊流模型模拟大型浅水湖泊的风生流场.在非结构化网格上采用有限体积法离散控制方程,提高了计算精度和效率,运用SIMPLEC算法进行数值求解,克服了为简化计算对二维物理机制常采用-维化数值处理的缺陷,使计算的流场更符合实际流场,并模拟分析了不同风向,风速下博斯腾湖大湖区水流运动特性.     

二维溃坝波传播和绕流特性的高精度数值模拟

本文建立了二维浅水方程的高分辨率差分模型，即将浅水方程作空间差分分裂，分别沿x、y方向应用组合型的通量限制二阶TVD格式，采用Van Leer的MUSCL型限量函数，用以解决二维溃坝的计算问题.首先分别与一维理论解和其它二维结果的比较，表明本文的方法非常成功.然后对全溃和部分溃情况下的溃坝波传播和绕流问题进行了数值研究，给出了精细的数值结果，揭示了其复杂的运动特性.     

一种Godunov算法及其在非平底流污染物传输中的应用

采用和谐的加权平均通量(Weighted Average Flux,简称WAF)算法,研究了浅水波方程的间断解及污染物传输问题。该算法采用WAF格式和HLLC Riemann求解器近似单元边界数值通量,中心差分格式离散地形源项,然后理论上证明了该算法是和谐的。最后利用WAF算法对非平底地形上浅水波间断解及污染物传输问题进行数值计算,精确地捕捉到了间断解和污染物运动过程,结果表明该算法满足守恒性,具有高分辨率、无振荡及捕捉污染物运动边界的能力。     

DEASM浅水流模型对热力环流的非结构网格模拟

为提高热电厂的取水安全,缓解废热排放造成的环境污染,从全场精细数值模拟的角度,推导了水深平均意义下的通用显格式代数应力模型(DEASM),数值离散方法采用SIMPLE程式下的非结构网格算法,并利用改进的QUICK格式来提高对流项模拟精度。该模型成功实现了对试验下的复杂热力浅水环流的精细模拟,结果表明模型模拟的热力浅水环流的断面流速分布、局部环流流线形态、环心位置、流线分离点以及温度场分布均与实测值吻合良好,初步表明该模型能够为统一描述浅水热力环流近区和远区问题提供一种更精细而通用的全场模式。     

二维对流扩散方程非均匀网格上的高阶紧致差分方法

利用降维法导出了非均匀网格上二维对流扩散方程的高精度紧致差分格式, 对于离散得到的代数方程组采用迭代法求解. 数值算例表明, 在相同网格节点数的情况下, 本文基于非均匀网格格式较均匀网格格式具有高精度, 高分辨率的优点, 对于含边界层的对流扩散问题具有很好的适应性.     

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.     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

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.