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水垫塘三维紊流数值模拟及消能分析 总被引:10,自引:2,他引:10
开发了能模拟复杂紊流的三维数学模型,编制了大型计算程序,针对拉西瓦水垫塘进行了数值模拟,揭示了水垫塘内速度,压力,紊动能及其耗散率的三维分布规律,获得了详细的水垫塘流态特性。研究了水流紊动扩主消能特性,反映出紊动和消能大量地发生在射流轴线附近,计算所得的底板最大冲击动压与实验值进行了比较,二者符合良好。 相似文献
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水垫塘内淹没冲击射流中的大尺度涡结构及其特征 总被引:3,自引:1,他引:2
高坝下游水垫塘消能与防护问题目前尚未得到妥善解决。本文应用现代紊流理论的观点,对水垫塘内的复杂流动结构进行了系统的研究,对主射流区的大尺度涡体和壁射流区的紊动涡体的拟序结构进行了分析,从紊流力学的角度对脉动压力的起源及水垫塘内水体能量的转移与耗散做了机理性解释,为高坝下游水垫塘的消能与防护的进一步研究提供了理论依据。 相似文献
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高拱坝多股挑流水舌入水优化间距的研究 总被引:2,自引:0,他引:2
应用紊动射流理论,对高拱坝多股挑流水舌在水垫塘中扩散的水力特性 和水流流态进行了分析,提出了多股挑流水舌入水优化间距的数学模型,试验资料验证表明,该数学模型简单可行,研究成果可为高拱坝水垫塘水力设计参考。 相似文献
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小湾水垫塘水力特性及设计优化研究 总被引:1,自引:0,他引:1
小湾拱坝坝身泄洪消能的技术难度已达世界当前最高水平,其水垫塘的优化设计亦是工程中的一大难题。本文通过承担完成国家“八五”科技攻关项目课题研究任务,在对小湾坝身泄洪消能布置方案进行水力模型试验的基础上,应用二维和三维紊流数学模型对多层和多股淹没射流水垫塘流动特性进行了数值模拟,对水垫塘三元流速场和壁面脉动压强的水力特性进行了实测研究;通过对多层射流入流方式的优化计算和实验验证,提出了“1+1<1”效应的新观点和最佳入流方式。用人工掺气方法,研究了掺气射流特性,得出了水流掺气可导致时均压强减小,脉动压强增大的结论。文中还讨论了小湾水垫塘采用全面混凝土衬砌的必要性,并对水垫塘底板高程、长度及体型提出了新建议。 相似文献
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本文论述了高拱坝下水垫塘设计目标,科研及应用现状,水垫塘消能控制工况。表、中孔各自单独泄洪与表、中孔联合泄洪的水流流态及动水压力。论述了水势塘允许动水压力,水垫塘的长度与二道坝的位置。在高拱坝大流量,大功率条件下.采用集中泄洪,集中消能的原则及体型优化措施后,获得较好的消能效果。 相似文献
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带有自由表面紊流流场的数值模拟 总被引:3,自引:0,他引:3
带有自由表面的三维强紊动水流在水利水电工程中,以及其他一些领域普遍存在.对该种紊流的数值模拟历来是一个十分具有挑战的领域.应用双流体模型与传统的标准κ—ε双方程紊流模型相耦合,对水垫塘中紊流流场进行了数值模拟、数值计算结果与物模测量结果具有较好的一致性。 相似文献
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对高拱坝泄洪消能中的若干突出问题进行了综述与分析。针对其泄洪消能特点,探讨了解决消能防冲的基本途径,如坝身孔口布置及与之适当的坝下消能形式(水垫塘)。分析了水垫塘内水流结构与消能机理,从而要求水垫塘有足够的消能体积与水垫深度。提出了关于水垫塘体型设计的防护标准及底板防护措施的若干意见。 相似文献
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水垫塘不同水流结构区掺气浓度分布规律试验研究 总被引:1,自引:0,他引:1
为了得到水垫塘局部掺气浓度分布规律,减少过流边壁空蚀破坏的发生,采用水力学模型试验的方法,将水垫塘内水体进行水流结构分区,通过改变泄流流量、水流入射角度、水垫深度三个条件,实测水垫塘不同水流结构区掺气浓度值,研究气体在不同水流结构区的运动机理。对试验所测数据进行整理得到水垫塘不同水流结构区掺气浓度分布曲线,且不同的水力条件与其拟合近似为二次曲线关系。通过分析得到水垫塘不同水流结构区掺气浓度分布规律如下:各水流结构区掺气浓度随泄流流量增大而增大;射流与附壁射流区紊动掺混随泄流流量增大而更加剧烈;掺气浓度随水垫深度增大而减小;淹没射流区与旋滚区掺气浓度随水流入射角度增大而减小,附壁射流区掺气浓度随入射角度增大而增大,但变化不明显。 相似文献
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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。 相似文献
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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. 相似文献
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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. 相似文献
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V. K. Konovalov O. V. Yashkin V. V. Ermakov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2008,42(2):105-109
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.
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Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008). 相似文献
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Peter B. Bayley 《河流研究与利用》1991,6(2):75-86
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. 相似文献
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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。 相似文献