低弗汝德数闸后淹没水跃的数值模拟

通过求解雷诺时均Navier-Stokes方程,对弗汝德数为3.19的淹没水跃进行了数值模拟。应用标准k-ε模型和RNG k-ε模型结合VOF(volume of fluid)自由表面跟踪技术,得到了淹没水跃自由表面位置、纵向速度、紊动能及速度矢量等变化情况。结合实验数据,详细对比研究了两种模型的模拟结果,分析了Fr=3.19淹没水跃的内部流场特性。研究表明RNG k-ε模型能更好的模拟低弗汝德数下淹没水跃的紊流结构,给出了2X/Y124为水跃发展区,并得出水跃产生的旋滚对紊动的产生和耗散起着重要作用。     

闸堰下游淹没水跃特性研究

本文通过试验分析，对具有驼峰堰的泄水闸下游平底消力池中的淹没水跃特性进行了研究，认为：当淹没水跃的前佛氏数Ｆｒ１＝３．４－７．３，淹没系数Ｓ＜０．７时，消力池及其下游的流态不会因水跃被淹没而恶化，淹没水跃的消能效果优于自由水库。     

淹没水跃的逆向流速

本文描述了对溢流建筑物下游产生的淹没水跃进行的试验研究。当下游明渠的尾水深度超过亚临界水深时，即产生淹没水跃。这种情况很常见，特别是在低溢流结构中。淹没水跃产生的涡流具有巨大的逆向自由表面流速，这种现象经常使粗心游客受伤害，因此又被称为“淹没机器”。通过理论推导和试验论证，我们定量分析了在各种水力上的危险高流速。     

淹没水跃Fr数对消能率影响数值模拟研究

淹没水跃具有一定的淹没度和紊动性,同时还具有变化复杂的自由液面,在水利工程中主要发挥着消能的作用.通过对淹没水跃流态与实际消能率的深入研究发现,低Fr数淹没水跃的实际消能率与名义消能率差距较大,而且经验公式计算的消能率值是偏大的,低Fr数水跃常见于平原地区的水利工程中,因此在对其消能设施设计时应引起足够的重视.     

溢流坝下游平底消力池淹没水跃特性的探讨

本文通过作者自己的试验,并与哥文达和拉贾纳南等人的试验相对照,对采用淹没水跃消能是否会给下游造成更严重的冲刷这一问题进行了探讨。试验证明,设有闸墩的溢流坝下游采用水跃消能,淹没系数S<0.7时,对护坦下游不会由于从自由水跃过渡到淹没水跃而带来不利的后果,相反会对减小水面波动和河床冲刷带来一定的好处,即淹没水跃跃首佛氏数F_1=3.4～7.1、淹没系数S<0.7时,消能效果比自由水跃好。     

三维紊流数值研究

本文针对复杂三维水流所具有规则边界、自由表面及各向异性，引入通度概念处理不规则计算边界，用ＶＯＦ法追踪自由表面，采用修正的ｋ－ε模型封闭Ｒｅｙｎｏｌｄｓ方程，分别计算了实用重力坝及其下游戽式消力池中水流流场和一个三维水跃流场。计算结果较好地与实验结果符合。     

小石峡水电站导流兼深孔泄洪洞消能工优化试验

通过新疆库马拉克河小石峡水电站导流兼深孔泄洪洞原设计方案的消能工试验,发现消力池内发生淹没水跃,水跃旋滚区与闸后射流相叠加,使陡坡段水流剧烈脉动。为了防止护坦段在较大的动水荷载下发生振动和破坏,采用在消力池内设置不同于传统布置方式的悬栅式消能工的方式,即从闸后陡坡末端起布置悬栅,悬栅的安装高度随水跃跃高逐渐抬高,呈台阶式布置。试验表明,台阶式布置悬栅起到了破碎水跃上部剧烈回旋运动的表面旋滚的作用,增大了回流的阻力,从而使水跃向下游移动,由淹没式水跃转化成稍有淹没水跃;在悬栅作用下,陡坡段和消力池内水流脉动明显减弱,浪花溅起高度明显小于加悬栅前的高度,这种悬栅布置方式可为其他同类工程提供参考。     

陡坡后消力池内水跃的数值模拟

利用三维RNG k-ε紊流模型和体积率(VOF)跟踪自由水面的方法,对4种不同工况、相同坡角的陡坡后消力池内的水跃特性进行了数值模拟,并与模型试验结果进行了对比.结果表明,不同工况下消力池内水面线特征、流速和水跃长度与模型试验吻合较好,陡坡后消力池内淹没水跃长度大于自由临界水跃长度.同时,数值计算与试验结果均表明,陡坡后消力池内水跃长度不能按照平底矩形水跃长度计算公式进行计算,必须考虑淹没度的影响,从而有效避免陡坡后消力池设计中的不足.     

淹没水跃激起闸门振动浅析

闸门振动是水利水电工程中较为普遍的现象。文章对闸门下游淹没水跃作用在闸门上的脉动压力试验研究成果作了简要综述，并结合某工程，对淹没水跃引起闸门振动作了浅析     

基于非结构化网格上的三维微幅自由表面流动非静压数值模型

建立了基于非结构化网格求解三维微幅自由表面流动非静压数值模型。一种有限差分法和有限体积法相结合的方法被用来在非结构化网格上离散控制方程。模型中采用分步法,以使压力项分解为静水压力项和动水压力项来单独处理。在每一时间步,得到关于水位和由压力泊松方程得到的动水压力的稀疏的线性方程组。模型是质量守恒的和对于重力波速、风应力、底摩阻、垂向黏性无条件稳定的。通过三个非恒定微幅自由表面流动算例的数值解和解析解的比较,验证了本文所建立的模型能够准确有效的预测三维微幅自由表面流动。     

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。     

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。     

Fish assemblage response to recent mitigation of a channelized warmwater stream

Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd.     

NUMERICAL STUDY OF WAVE EFFECTS ON SURFACE WIND STRESS AND SURFACE MIXING LENGTH BY THREE-DIMENSIONAL CIRCULATION MODELING

1. INTRODUCTION Coastal and continental shelf regions are characterized by intensive interaction between wave and current. These regions are of great economic significance to mankind. Therefore, the modeling of wave and current as well as their mutual int…