溢洪道挑流鼻坎水气二相流数值模拟研究

针对某溢洪道挑流消能存在的问题,采用VOF方法、立方体网格和k-ε紊流模型对溢洪道整体水力特性进行了三维数值模拟,对挑射水流流态、水舌掺气、水垫塘底板压强、下游河道流速等方面进行了分析。将某溢洪道由原高低式挑流鼻坎修改为差动式后,增大了下泄水流入水范围,提高了挑流消能的消能效率,减小了水垫塘底板压强,降低了下游河道水流流速。优化方案数值模拟结果得到了模型试验结果的验证。     

带掺气槽岸边溢洪道挑流消能工水力特性

采用RNGk-ε双方程紊流模型对掺气槽、差动式挑流鼻坎和预挖坑联合运行的岸边溢洪道水流流场进行研究,模拟了具有大曲率水气交界面的挑射水舌和掺气坎水流,分析讨论泄槽流态、掺气槽底板最大冲击压力和差动式挑坎压力分布,给出了挑射水舌以及预挖坑的水流结构与速度分布特性,并将计算值与实验值进行对比,两者吻合良好。研究结果表明:泄槽中4道掺气槽的设置能有效减免发生空蚀破坏,但对泄槽中水面有一定的影响;高扩散低收缩差动式挑流鼻坎与预挖坑的联合运用消能效果理想。     

云龙水库溢洪道泄洪消能设计方案

云龙水库是昆明市掌鸠河引水供水工程的水源工程.泄水建筑物采取泄洪隧洞与溢洪道联合泄洪.溢洪道挑流鼻坎采用不对称窄缝式挑流鼻坎,既可以使水流纵向扩散而达到消能的目的,又改善水舌方向,是理想的挑坎型式.     

察汗乌苏溢洪道流场二维和三维数值模拟对比

为了选择较为理想的研究溢洪道水流特性的数学模型,结合察汗乌苏水电站工程实例,利用数学模拟对其溢洪道流场的水流特性分别进行了二维和三维模拟,分析其可行性和存在的问题。采用标准的k~ε紊流模型描述水流流动、VOF模型跟踪水流自由表面,得到水深、流速和压力等一系列水力要素计算值,并将他与物理模型试验数据对比验证,结果基本吻合。分析研究表明:二维模拟完全满足溢洪道挑流鼻坎段前的水力特性研究需求,如若重点关注挑流鼻坎段水力要素特性,则建议使用三维数值模拟。     

开敞式宽大单泄槽溢洪道水力特性及优化布置研究

开敞式宽大单泄槽溢洪道与一般溢洪道相比易发生水流流态复杂、掺气效果差等工程安全问题。以马来西亚Baleh水电工程为例,采用VOF法与RNG k-ε双方程紊流模型对溢洪道流场进行三维数值模拟。计算分析了不同工况下溢洪道流态、流速、沿程压强等水力特性的分布规律。同时开展1∶50物理模型试验,对比分析数值模拟结果与模型试验结果发现,两者基本一致,验证了开敞式宽大单泄槽溢洪道水力特性数值模拟的准确性与可行性。进而利用紊流模型计算分析了溢洪道掺气坎的优化布置方案,结果表明:1#掺气坎抬高20 cm后,坎后掺气空腔长度由11.03 m增大至19.84 m,消能率提高了6.11%;3#掺气坎沿泄槽陡坡上移15 m后,挑流水舌冲击位置上移,减轻了对挑流鼻坎段水流流态的影响。研究结果对同类工程的优化设计有一定的借鉴作用。     

溢洪道差动式挑流鼻坎挑距和冲深特性探讨

溢洪道差动式挑流鼻坎可明显增加挑射水流在空中的碰撞、紊动和掺气,大大减轻下游河床的冲刷.根据部分溢洪道工程的水工模型试验资料,对差动式挑流鼻坎挑射水舌挑距及其下游河床冲刷坑深度的估算方法进行分析和探讨,可供类似工程设计和运行参考.     

威远江水电站溢洪道挑流鼻坎数值模拟研究

针对威远江水电站岸边式溢洪道挑流消能存在的问题,采用RNGk-ε双方程模型、非结构网格与自适应局部网格加密的方法,模拟湍流,利用流体体积分数法(VOF)确定自由水面线,成功地对溢洪道挑流鼻坎挑流进行了三维紊流数值模拟。对挑流鼻坎的修改方案进行了研究,经过计算提出了较优方案,所提方案得到了物理模拟的验证,为威远江水电站设计与优化提供了可靠的设计依据。     

溢洪道出口窄缝挑坎特性研究

消能工体型的选择在水利工程设计中至关重要。采用RNG k-ε紊流模型与VOF方法对泄洪过程中溢洪道与水垫塘内的水流进行水气二相流三维数值模拟,研究窄缝型挑坎消能工的水流特点及规律,结果显示,数值模拟计算的水深、水流流态、入水角度等参数与模型试验结果吻合较好,验证了数值模拟的可行性。在此基础上,计算分析了窄缝型挑坎收缩段水流及空中水舌的水力特性,以及水垫塘底板压强分布规律,确定出窄缝型挑坎最大压强所在位置及空中水舌流速变化规律。研究结果表明：窄缝型挑坎束窄水流作用明显,其空中水舌同一横断面的最大流速位置基本相同,同一纵向断面垂向流速差沿程逐渐减小,挑坎收缩段底板处流速大小呈抛物线形分布,而压强分布沿程呈现3个区间3个趋势的分布规律。研究成果可为实际工程中同类型消能工的设计提供参考。     

某工程溢洪道挑流鼻坎的模型试验

以某工程溢洪道挑流鼻坎为研究对象,采用物理模型试验的研究方法,以同等工况为试验研究前提,不同挑流鼻坎形态为研究方向。经试验得出不同鼻坎体型对应消力池下游水流流态、水流挑距、河床入射水流形态及河床冲刷形态。观测分析对比,得到适用于该工程实际的溢洪道鼻坎体型。     

大圆弧导向鼻坎在昌马水库溢洪道改建中的应用

在昌马水库多年的泄洪运行中发现,其溢洪道泄洪出口水舌落点集中,在岸边形成较深的冲刷坑,直接威胁到岸坡的稳定安全。为了解决该问题,通过溢洪道挑流鼻坎改建方案的水工模型试验研究,调整挑流鼻坎体形,提出了适用范围较广的大圆弧导向鼻坎改建方案。经过模型试验验证,大圆弧导向鼻坎不仅具有很好的导向功能,有效控制水舌落水位置、分布及范围,而且能使水舌沿横向、纵向拉开,使水舌覆盖消能区较大范围,减轻河床冲刷,有效解决昌马水库溢洪道存在的问题。     

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。     

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.     

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.     

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。     

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.     

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.     

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.