基于CFD技术的水轮机性能预估

CFD计算流体力学作为一门不断发展和成熟的学科已在航空、能源、水利等相关领域得到广泛应用.介绍了CFD技术及其应用,通过对水轮机内部流场进行CFD分析,可以提供各流动部件损失计算的数据进而计算出水轮机的效率.总结了较精确的水轮机各部件水力损失计算公式,指出了现有的水轮机性能预估方法存在的难点和问题,提出了一些新的见解.     

藏木水电站高比速混流式水轮机优化设计

结合藏木水电站高比转速水轮机参数优化项目,通过CFD分析,对模型水轮机的蜗壳、尾水管、转轮等水力过流部件进行了全面优化设计。通过模型试验验证,藏木水电站水轮机水力性能研究达到了预期目标,CFD分析结果与模型试验结果基本吻合,为高比转速转轮的水力性能优化提供参考。     

混流式水轮机全流道三维定常湍流数值计算

基于标准k-ε双方程湍流模型和三维时均N-S方程,进行了混流式水轮机全流道的三维定常湍流计算.捕捉到了水轮机各过流部件内的流场和尾水管内的涡旋结构等流动信息.结果表明,水轮机的全流道CFD分析能够较为准确地预测出水轮机过流部件内的性能参数及内部流场结构,所得到的结果对进行水轮机的水力设计或改型优化设计等研究具有重要的指导意义.     

混流式水轮机引水部件内部流动的二维数值模拟与三维模拟比较分析

基于N-S方程和标准k-ε紊流模型,采用CFD计算流体力学软件对HLA 616-WJ-55混流式水轮机原型机的引水部件在最优工况下进行了二维定常数值模拟,获得了流场的速度、压力分布变化规律,并与同型式水轮机的蜗壳三维数值模拟结果进行比较分析。结果表明,二维CFD分析也能较概括地预测引水部件内部流场的结构,数值模拟结果对水轮机选型和优化设计均具有重要的指导意义。     

水轮机设计及改造最新技术——CFD技术

文章就当今水轮机设计及改造中采用的最新技术CFD技术－计算机模拟流态分析技术作了概要说明，它给了我们一种全新的水轮机设计理念；同时对水轮机模型试验中CFD技术的应用－NTS（数字试验台），作了说明与介绍。随着计算流体力学及大功率计算机的发展，此项技术正在成为水轮机设计与改造的主流。     

混流式水轮机内三维定常湍流数值研究

基于 k-ε紊流模型和三维时均N-S方程,进行了混流式水轮机全流道的三维定常湍流计算.捕捉到了水轮机过流部件内的流场和非最优工况下转轮通道及尾水管内的旋涡结构与演化特征等流动信息.结果表明,水轮机的全通道CFD分析能够较为准确地预测出水轮机过流部件内的性能参数及内部流场结构,所得到的结果对进行水轮机的水力设计或改型优化设计等研究具有重要的指导意义.     

双涡轮灯泡贯流式水轮机三维 定常流动解析

基于三维N-S方程及标准紊流模型,对双涡轮灯泡贯流式水轮机进行了全三维定常流数值模拟,获得了流场的速度、欧拉能量及压力分布等变化规律。结果表明,CFD分析能较准确地预测双涡轮贯流式水轮机内部流场的结构, 其数值模拟结果可以作为双涡轮贯流式水轮机优化设计及运用的依据。     

水轮机长短叶片转轮三维数值模拟

基于Standard k-ε双方程湍流模型和三维时均N-S方程,进行了混流式水轮机HLA351长短叶片转轮流场的三维湍流数值模拟研究,获得了流道的流速和压强分布.计算结果表明:和常规转轮相比,长短叶片结合的转轮流态较好,流速和压强分布合理,水轮机的全流道CFD分析能够较为准确地预测出水轮机过流部件内的性能参数及内部流场结构.     

联合BIM和CFD的混流式水轮机蜗壳水力设计

为了探索BIM技术在水力机械设计中的应用，高效模拟设计产品的水力性能，开展了联合BIM技术与CFD的水力机械设计研究。分析了BIM与CFD联合应用的流程以及二者数据交互的方式。以HLFN-LJ-930混流式水轮机为例，将水轮机蜗壳作为重点，对其进行了水力设计，构建了水轮机BIM模型。借助RNG k-ε模型，应用Fluent软件对水轮机全流道流场进行了仿真模拟。模拟结果显示：不同工况下蜗壳BIM模型流场压差较小，速度分布均匀合理，水力性能良好。研究结果表明BIM模型能够为数值模拟提供计算模型底板，有效模拟出水轮机的水力特性，验证了BIM与CFD联合应用于水力机械设计的可行性，对类似水力机械的设计具有一定的借鉴意义。     

采用CFD研究双击式水轮机水力设计

主要介绍采用计算流体动力学(CFD)对双击式水轮机水流进行模拟。定性研究表明CFD是水电设备水力设计和分析的工具。     

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.