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…     

管道截面突变处的局部阻力系数

不可压紊流流经管道截面突变处，截面积之比和流速分布不均匀性对局部阻力系数有影响。流速分布符合幂次律。利用流体流过管道截面突变处的动量变化和能量变化。求出了损失的能量，从而得出管道截面突然扩大处的局部阻力系数ξ＿１；仿照计算ξ＿１的关系式，给出了管道截面突然缩小处的局部阻力系数ξ＿２。从计算结果来看，当小直径截面的雷诺数大于２×１０￣（６）时，计算管道截面突然扩大处的局部阻力系数ξ＿１，速度分布可作为均匀分布来处理；当小直径截面的雷诺数大于７３００时，计算管道截面突然缩小处的局部阻力系数ξ＿２，速度分布可作为均匀分布来处理。理论计算与实验结果对比表明，两者之差平均不超过０．０６。所以本文给出计算管道截面突变处的局部阻力系数的关系式是可行的。     

长江口沉积物粒度参数的统计规律及其沉积动力学解释

对长江口表层底质样品粒度参数的统计表明：１．沉积物在总体上表现为水下环境粗于潮滩，口内河道粗于口外海滨，南支粗于北支．北港粗于南港；同时．河道在纵向上有自上游向下游变细、横向上有自深槽向浅滩变细的趋势．２．平均粒径Ｍｚ（φ）普遍大于φ＿（５０），特别是粉沙级样品．两者差值最大可达１．４４．３．粒径的标准偏差σ＿１与平均粒径Ｍｚ之间存在良好的线性正相关关系，相关系数一般大于０．９０．４．９７％的样品粒径的偏度ＳＫ＿１大于０．与波浪作用为主的海滩ＳＫ＿１大部分小于０形成鲜明的对比．５．概率累积曲线上跃移和悬移组分之临界粒径Ｃ（φ）以及悬移组分含量Ｓ（％）均与Ｍｚ有良好的正相关关系，其中受絮凝作用干扰的口外海滨相关系数相对较小．相关方程差异较大．对以上规律，从沉积动力学角度做了较为合理的解释．     

渔洞水库入库月径流过程的随机模拟

本文以实测４２年径流资料为基础，分别采用季节性ＡＲ（１）、季节性ＡＲ（２）、季节性ＡＲ（３）、季节性ＡＲ（１）－ＡＲ（２）混合和季节性ＡＲ（１）－ＡＲ（２）＿ＡＲ（３）混合模型对渔洞水库径流过程进行随机模拟，得出１００个样本，最后通过对所得径流样本中种参数的统计分析，推荐出最佳模型。     

表征生态状况的综合干旱指数构建及干旱风险分析

联合标准化降水指数、标准化土壤湿度指数、标准化地下水指数和标准化生态缺水指数,基于熵权法和相关系数赋权法分别构建了西北地区综合干旱指数CDI＿E和CDI＿C,分析了CDI＿E、CDI＿C与标准化叶绿素荧光指数(SSIF)、自适应帕尔默干旱指数(scPDSI)间的相关性,评估了CDI＿E、CDI＿C对植被状况的表征以及综合干旱的监测能力,并选取典型干旱事件进行验证。利用游程理论分析了1986—2015年西北地区的综合干旱特征及暴露度、脆弱性、恢复力3个风险因子,采用等权法计算综合干旱风险,依据10 a滑动窗口分析干旱风险的变化趋势。结果表明：CDI＿C考虑了干旱与植被的响应关系,且与scPDSI的相关性较强,能较好地反映西北地区的综合干旱情况;CDI＿C可以同时监测到气象、农业、地下水和生态干旱,且反映的干旱与实际情况一致;CDI＿C显示研究时段内西北大部分地区呈变湿趋势;综合干旱在新疆、青海等干旱半干旱区的发生频率较高且干旱风险较大,各区干旱风险呈先增后减的趋势。     

示差光度法在测定高含量NO_3~－—N中的应用

示差光度法在测定高含量ＮＯ＿３￣－—Ｎ中的应用贡丽，关虹，崔巍（山西省水文总站）１引言据文献报道，非金属元素中高含量的Ｆ￣－、ＣＮ￣－、、等都可用示差分光光度法测定，取得了较好的结果。而高含量的ＮＯ￣（－）＿３—Ｎ用示差光度法测定还未见报道。我们都知...     

小展弦比可控环量翼的风洞试验及其三维效…

本文对一小展弦比（λ＝１）可控环量翼进行了风洞试验，试验结果表明，由于存在着强烈的三维效应，若不采取有效的措施对三维效应进行抑制，则小展弦比可控环量翼三维流动的升力便远远小于二维结果（包括试验与计算）。针对这种情况，本文对小展弦比可控环量民翼的三维效应的抑制做了一些初步探讨。     

河工模型相似的精度及误差探讨

本文按照两个相似流动体系必须被同一个物理方程所描述的原理,由水流连续方程的比尺关系导出变态模型的质量守恒误差公式。采用矩阵特征值分析的方法,得到三维流时均流场紊动应力的特征值,并给出了它与模型变率的关系式．由它可分析一维总流分析中的紊动应力相似误差。从概率统计的角度利用实验资料给出泥沙沉降公式,并可与服从Gauss分布的概率公式联解计算出泥沙沉降分布,亦可用于泥沙沉降相似的经验公式λω=λu（λL／λh）^m中指数m的分析与计算。对目前常用的两种泥沙起动相似的经验公式进行分析,并比较了二者的相对误差。     

广州软土的压缩特性与修正剑桥模型参数λ和κ

修正剑桥模型是基于临界状态土力学理论建立的土弹塑性本构模型,在世界上得到广泛应用。 为获得修正剑桥模型参数λ和κ,需要对土进行等向压缩试验。然而,实际工程的土工试验报告通常仅提 供一维压缩试验得到的压缩指数Ｃｃ和回弹指数Ｃｓ,并不进行等向压缩试验。对广州原状软土进行了一 维压缩试验和等向压缩试验,试验结果表明,单向压缩试验与等向压缩试验下广州软土的压缩指数近乎 相同,而等向压缩试验下广州软土的回弹指数为单向压缩试验下回弹指数的１．４９～１．８７倍;Ｃｃ与其修 正剑桥模型参数λ比值为１．８８～２．３８,Ｃｓ与其修正剑桥模型参数κ比值为１．２～１．５４。试验成果可为广 州地区的工程设计、软土本构模型的建立提供参考数据。     

利用天然含水量与液性指数的关系快速确定土的状态

１问题的提出在土工试验中，通常的做法是由液性指数ＩＬ的大小确定土的状态，而液性指数是由公式ＩＬ＝（Ｗ－ＷＰ）／ＩＰ计算得来的（式中：Ｗ———天然含水量，ＷＰ———塑限，ＩＰ———塑性指数），从中我们看出ＩＬ值与Ｗ值有直接关系，它随天然含水量的变化而变...     

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。     

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。     

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.