直角Z形组合双弯管流动特性的研究

多片焊接弯管是火、核电厂循环供水管路系统中应用最多的形变件，最常见的安装形式是两个弯管的0°组合。当弯管间距较小时，会出现上、下游弯管管内流动的相互影响。本研究采用二维激光多普勒测速仪和五孔探针测得4片90°弯管Z形组合在不同弯管间距下水流特征断面上的三维流场、压力分布以及紊动特性的沿程变化等。并以此探求双弯管局部阻力相邻影响的机理。限于篇幅，本文仅对测得的水平直径轴向流速分布以及特征断面上二次流形态进行了分析，指出双弯管间相邻影响系数的变化规律受弯管二次流动、涡流区、弯管进出口流速核大小以及上、下游弯管间流速分布调整程度等4个方面的制约；弯管间过渡直管段的长短是改变局部阻力相邻影响的关键因素。     

90°弯管Z形组合局部阻力特性研究

90°弯管的Z形组合是电厂各种管路系统中典型的形变件组合形式,因管路布置空间狭小,故弯管间会产生不同程度的局部阻力相邻影响。采用Realizable k-ε湍流模型对两种间距的组合弯管进行数值模拟研究,采用间距为5倍管径的组合弯管试验结果对数学模型参数及方法进行了验证,并据此开展了间距为0的组合弯管数值预报模拟。通过对比分析两种组合弯管轴向流速、横断面二次流及阻力损失沿程变化,结果表明,两种组合弯管在下游弯管中流速分布表现出较大差异,弯管间距为0时下游弯管内水流轴向流速分布更加不均匀、二次流发展更成熟,组合弯管综合局部阻力损失更大。     

取代90度圆弯管的一种新型弯管

在各种工业管道系统中局部阻力往往占有很大的比重。为了节约能源,引起了国内外对局部阻力研究的重视。对90度圆弯管阻力问题的研究,目前应用于生产实际的经验公式、图表比较多,所得局部损失系数ζ的数值差别也较大。以下列所得ζ较小的经验公式为例式中:d──圆管直径;R──圆管曲率半径。主要是增加曲率半径R,就可得较小的ζ值。但最少也只能以0.131为极限。这里介绍一种可以取代90°圆弯管的新型弯管──90°椭圆形圆弯管。根据实验资料和理论分     

输水管线中弯管局部阻力的相邻影响

本文用实验方法对管道阻力计算中相邻弯道局部阻力的影响进行了系统的研究，提出了可供实用的弯管相邻影响系数；解释了弯管间局部阻力相邻影响的成因；分析了水利工程中类似的实例。提出为了合理地计及局部阻力的相邻影响，在计算总水头损失时应遵循的算法。     

柯列勃洛克公式中沿程阻力系数的计算方法

在水力计算中．计算沿程阻力系数λ的公式很多．其中包括大量的经验公式和半经验公式。实际应用中发现．在计算沿程阻力系数λ的诸多半经验公式和经验公式中．柯列勃洛克公式应用范围广．与试验结果符合良好。但是，由于该式应用比较麻烦．须经过几次造代才能得出结果，所以影响了该公式的实际应作用。本文将牛顿迭代公式和中点造代数值计算法应于柯列勃洛克公式中计算λ值．概念清晰，结果准确。     

柯列勃洛克公式中沿程阻力系数的计算方法

在水力计算中，计算沿程阻力系数λ的公式很多，其中包括大量的经验公式和半经验公式。实际应用中发现，在计算沿程阻力系数λ的诸多半经验公式和经验公式中，柯列勃洛克公式应用范围广，与试验结果符合良好。但是，由于该式应用比较麻烦，须经过几次迭代才能得出结果，所以影响了该公式的实际应作用。本文将牛顿迭代公式和中点迭代数值计算法应于柯列勃洛克公式中计算λ值，概念清晰，结果准确。1柯列勃洛克公式的应用范围柯列勃洛克公式表达形式为：1＿、，a2sl、二三—一月十（＿十千二三）（）人一””3·7dRe人式中L三一管道的当量粗…     

船闸输水廓道直角边缘单支孔充水阻力系数试验

介绍了船闸复合管地角边缘有单支孔充水阻力系数试验的主要结果。包括；阻力系数影响因素分析，模型设计，试验和对试验结果的讨论；在此基础上，拟合了计算直角边缘单支孔充水阻力系数的经验式。     

船闸输水廊道直角边缘单支孔充水阻力系数试验

介绍了船闸复合管直角边缘单支孔充水阻力系数试验的主要结果。包括:阻力系数影响因素分析，模型设计、试验和对试验结果的讨论；在此基础上，拟合了计算直角边缘单支孔充水阻力系数的经验式。     

渐扩式水跃跃后水深的计算

分析渐扩式水跃局部阻力系数随一般二元水跃局部阻力系数变化的规律,利用能量方程推导渐扩式水跃跃后水深的计算公式,得出了渐扩式水跃新的计算方法和跃后水深新公式,通过实际工程和已有公式对其正确性进行了验证。分析认为,在工程应用范围内(扩散角θ9°),渐扩式水跃局部阻力系数与二元水跃局部阻力系数呈对数关系;提出的共轭水深新公式能满足工程运用要求,并且计算的跃后水深随着跃前断面弗劳德数的增大与已有公式计算的跃后水深值的偏离程度逐渐减小。     

砂质河道桥墩局部冲刷计算经验公式改进和验证

桥墩局部冲刷深度是桥梁设计的重要参数，但随着造桥技术的发展，桥墩局部冲刷计算的经验公式在计算尺寸较大的桥墩局部冲深时误差偏大。为解决此问题，在前人的研究基础上，根据统一量纲的原则建立了砂质河道桥墩局部冲刷深度经验公式，并考虑基台露出床面对冲刷的影响，对公式进行修正。将文中提出的公式与中美计算规范进行比较，结果表明：所提出的公式具有考虑因素较全面、量纲统一、适用于大型桥墩局部冲刷深度计算的优点；计算精度相比另外3种公式有较明显的提高，能更好地预测桥墩局部冲刷深度。研究成果可为桥墩布设、施工与防护等提供技术支撑。     

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。     

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。     

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.     

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。     

浅谈天湖水电站水轮机运行故障及处理措施

简述天湖水电站投运以来各种故障的表现形式，分析其原因，提出了相应的处理方法及措施，并对合理利用国内外设备提出建议。