三维宽顶堰紊流场数值模拟及分析

本文利用三雏标准k-ε紊流数学模型,选择VOF方法追踪自由表面,采用气液两相流计算模型对宽顶堰流场进行了数值模拟,计算结果与试验数据较为吻合.模拟结果表明,数值模拟能够广泛应用于数值模拟带有复杂自由表面的泄水建筑物紊流场.     

三维宽顶堰紊流场数值模拟与分析

本文利用三维标准k-ε紊流数学模型,选择VOF方法追踪自由表面,采用气液两相流计算模型对宽项堰流场进行了数值模拟,计算结果与试验数据较为吻合.模拟结果表明,数值模拟能够广泛应用于数值模拟带有复杂自由表面的泄水建筑物紊流场.     

二维流冰消融数学模型

本文采用水深平均κ－ε以方程紊流模型与流冰扩流体模型首次推出了适合于天然实际工程水域复杂条件的紊流流冰消融数学模型。模型还利用离散型动态边界拟合坐标变换系统以适应天然水域的不规则边界与复杂流态，对天然流场中常出现的露滩、断流、动态水边界及几何曲率影响等特殊数值计算问题的处理颇有实效，具有较大的实用价值。本文以丹东电厂温排水缓冰工程为例验证了数学模型。     

基于FLUENT软件的闸后水跃二维数值模拟

本文采用标准k—ε湍流模型封闭Reynolds方程作为紊流控制方程组，用几何重构VOF法追踪自由表面，流场计算用PISO算法，对水闸后水跃强紊流区流速场进行了数值模拟；用毕托管测水跃流速，将数值模拟结果与实测结果进行了比较，表明了算法的可行性与实用性。     

非正交曲线坐标下二维水流计算的SIMPLEC算法

本文采用Laplace方程坐标变换方法生成正交曲线网格，并对浅水流动的控制方程进行坐标变换，方程离散时采用B型交错网格。利用“水位扫描法”结合壁面函数法来处理移动边界，用SIMPLEC算法解非正交曲线坐标下的κ-ε双方程紊流模型，修正了由网格的非正交性引起的误差，通过对美国Colorado洲Fall River的资料进行流场验证，计算结果与实测资料基本符合，显示了本模型在不规则水域计算中的实用价值。     

中间渠道内非恒定流数值模拟

利用平面二维非恒定流数值模型，来研究中间渠道内非恒定流问题，该模型基于任意三角形计算网络，采用隐式求解自由表面的剖开算子法，离散求解控制方程，有效地处理了非线性混合算子和计算自由表面的困难，避免人工滤波措施，提高了计算精度和计算稳定性，并在三峡通航工程方寒比较中得到应用。计算结果表明，该模型能较好地反映中间渠道内水充特征，与分析模拟船闸不同运动方式下渠道内水流波动特性，达到优化运行方案，改善渠道内     

一种简便的非交错曲线网格三维水流数值模型

在平面非正交曲线，垂向采用σ-坐标系统条件下，建立非交错网格变量布置的水深-流速迭代计算模式。由水深校正法求解水体自由表面和流速场耦合问题，为避免压力场波动，采用动量插值方法计算交界面处流速插值。运用该模式模拟了南京河段天然“S”型弯道三维水流流动。     

二维非恒定空化流的数学模型

本文提出了一个新的数学模型,用于预测高Reynolds数的二维紊流场中非恒定空化流的形成与发展过程及其内部结构。将空化流看成是泡-液两相流动,采用宏观与微观两个尺度来描述其流动形态与内部结构。宏观尺度主要用于空化区及其外部紊流场的计算,微观尺度用于确定气核在紊流场中的运动及生长过程,宏观与微观两种分析相互结合,前者应用两相流模型及现有紊流场分析技巧,后者采用泡动力学理论,应用这一模型,可对二维紊流场中空化流的演变过程及其非恒定特性给出比较清楚的数值描述。     

中间渠道内非恒定流数值模拟

利用平面二维非恒定流数值模型，来研究中间渠道内非恒定流问题，该模型基于任意三角形计算网络，采用隐式求解自由表面的剖开算子法，离散求解控制方程，有效地处理了非线性混合算子和计算自由表面的困难，避免人工滤波措施，提高了计算精度和计算稳定性，并在三峡通航工程方案比较中得到应用。计算结果表明，该模型能较好地反映中间渠道内水流特征，与分析模拟船闸不同运行方式下渠道内水流波动特性，达到优化运行方案，改善渠道内航行条件的目的。     

天然河流中污染物排放远区浓度分布的数值计算模型

本文建立了一个适合于自然河流中污染物排放的远区计算模型。该模型的计算特点是将流场和深度场分开计算，即所谓“非偶合解”，运用ＳＩＭＰＬＥＣ方法计算了流场，用改进的ＱＵＡＬ－ＩＬｍ和ＱＵＡＬ２Ｄ方法计算了浓度场。该模型应用于长江汉江仙桃段，其计算出的流场和ＣＯＤ浓度场与实测值基本一致。     

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。     

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。     

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.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.