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。     

空气阻力系数对水滴运动及蒸发的影响

应用喷灌条件下水滴的运动、蒸发及分布模型对水滴的飞行时间、飞行距离以及蒸发率进行了预测，对由五种空气阻力系数计算公式（Bird、Park、Fukui、伊沙叶夫、Wallis）求得的预测值和实测值进行了比较。结果表明：应用Bird、Wallis、Fukui公式预测的水滴飞行时间与实测值的变化趋势一致；五种阻力系数公式中，应用伊沙叶夫公式求得的水滴飞行时间预测值与实测值的相对误差最小；五种阻力系数公式均能较准确地预测水滴飞行距离，其中Park公式的预测精度最高；五种阻力系数公式对于单个水滴蒸发率的预测结果与实测值较接近，而Fukui公式对总体蒸发率的预测值与实测值的平均相对误差最小。     

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。     

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.     

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.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.     

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。     

Serial discontinuities in a Rocky mountain river. II. Distribution and abundance of trichoptera

River regulation in the headwaters and middle reaches of the Gunnison River, Colorado, significantly altered distributions and abundances of Trichoptera fauna. Twenty-five species were collected from mainstream samples, with the greatest species richness occurring at an unregulated, rhithron segment above the central reach dams. At sites immediately below the three hypolimnial-release dams and a reregulation dam, species richness was reduced 35–90 per cent and abundance > 95 per cent. Net-spinning caddisflies were the dominant trichopterans at unregulated sites; Arctopsyche grandis in the upper reaches (218 organisms, 586 mg dry mass m^?2) and Hydropsyche cockerelli, H. occidentalis and Cheumatopsyche pettiti in the lower river (9041 total organisms, 6621 mg m^?2), downstream from the last dam. The observed distributional pattern of low trichopteran densities in dam tailwaters and high hydropsychid densities at sites 60–80 km below the central reach dams is a classic expression of continuum resets and adjustments in response to stream regulation as predicted by the Serial Discontinuity Concept.     

Changes in Summer Irrigated Crop Area and Water Use in Southeastern Turkey from 1993 to 2002: Implications for Current and Future Water Resources

Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold (from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead to improved management, and by extension, sustainability of water resources in the region.     

Surveying for Water Resources

Abstract

A professional Land Surveyor (Geomatician) describes the Hydrogeologists' survey requirements of a major water resources assessment for the government of The Sultanate of Oman (1992 to 1996). The need for objective specifications is stated. Specialist terms like geoid, spheroid, Mean Sea Level are explained and how to relate spheroidal levels to the geoid. Methods like traditional survey, satellite survey, and photogrammetry are introduced. The paper encourages coordinated working for the benefit of water resource assessment and recommends employment of the professional land surveyor for major studies.     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.     

浅谈优化Vray渲染在制作三维场景的应用研究

用Vray三维渲染引擎来渲染三维场景,其质量和速度是由一些影响因素和参数设置决定的,不同的参数和因素,可以得出不同的三维渲染效果.因此,分析、优化三维渲染质量和速度的影响因素,正确、合理的选择参数对提高Vray最后渲染阶段的质量和速度非常重要.     

固结、渗流和沉积控制方程研究

本文从两相流体动力学的守恒方程出发，考虑固相、液相的相对运动，推导了可以考虑场的不均匀性和流体压缩性的统一形式的控制方程，并对方程所基于的物理概念和相互联系进行了必要的分析。通过对方程适当形式的表达，可导出用于大、小变形固结、渗流和沉积的简化方程，显示了在不同领域的三个理论存在一定的统一性。方程推导过程并未对本构关系加以限制，适用范围较广。依据实际问题的要求，作了不同形式的简化。