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为了对保水堰的交替水流进行数值模拟,依据保水堰恒定流情况下的工作特性,将保水堰的水流形态分成堰流和满流两种状态,分别建立保水堰不同流态下的非恒定流数学模型。分析两种不同水流形态的交替机理,建立两种水流的转换条件,联立两种不同形态的数学模型构成保水堰的堰流和满流交替的非恒定流数学模型。利用数值计算的方法对保水堰的水流交替情况进行了模拟,结果表明,通过将两种流态的方程进行组合,可以合理地模拟保水堰的水流交替过程。 相似文献
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自流压力输水管路保水堰最小安全超高分析 总被引:1,自引:0,他引:1
自流压力输水管路的保水堰是保证稳定供水和安全运行的重要工程措施。本文把调节池输水管道保水堰作为一个水力系统,分析保水堰的工作原理和运行特点,建立动态水流的数值计算模型。利用试验数据对计算模型进行验证后,采用数值方法对保水堰的水流特性进行模拟。结果表明,当输水系统停水时,长管道水流的惯性力作用可能引起调节池的水位跌落和波动,为了防止进水口发生水体脱空现象,保水堰的最小安全超高需大于上游突然停水时调节池的最大跌落深度,从而建立了保水堰安全超高的估算公式。 相似文献
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驼峰堰是由三段圆弧曲线复合而成堰面的一种低堰,具有结构简单,整体稳定性和断面应力分布较好,堰体低,流量系数高,堰前不易淤积,且对地基要求较低,设计和施工相对简便等优点,因而,国内中小型工程采用较多。本文结合青海雪龙滩电站溢洪道挑流消能方案的试验研究,在几何比尺为140的模型上,对该工程进口段采用的驼峰堰特定体形的水力特性进行了详细的观测,并着重对自由溢流时流量系数随堰顶水头的变化规律,淹没流态判别,淹没度分析及压力分布等进行了阐述。 相似文献
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介绍设有鼻坎曲线型低堰泄流能力,下游水流流态衔接变化规律的全过程,即水流流态衔接中的挑流,远驱水跃,底流,面流,波状水跃,波流和贯串其中的淹没流均能较明确地反应出来,同时整理了判别曲线型低堰产生淹没流流态的三种方法,另外,对波状水跃(1),(2),波流流态的概念作了简述,对淹没流的淹没条件了新的看法,供参考讨论。 相似文献
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保水堰是一种新型溢流堰结构形式,为提升保水堰在大型调水工程中的输水能力,利用实测数据进行模型
验证,在确保模拟保水堰堰内水流流态规律准确性的前提下,探究工程中保水堰体型参数对输水系统过流能力的
影响。研究揭示了堰井段环状旋涡区的产生与发展机理,并对 11 种降低堰高方案进行数值计算,分析堰井段流
速矢量分布和环状旋涡区范围及能量耗散的变化,发现使输水系统过流能力增加的最佳堰高区间为 [1.0?P1≥P≥
0.7P1](P 为保水堰堰高;P1为堰前堰高)。当堰高在此区间内,通过降低 P 使堰前流速矢量仰角和堰后环状旋涡
区变小,能量耗散显著降低,降低 0.1P1,流量平均增加 2.1%。考虑到工程改造成本和过流能力提升效果,故在本
研究提出最佳堰高区间内修改保水堰的结构,为输水系统过流能力提升提供参考。 相似文献
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本文通过历史观测数据,分析闸孔过流特征,确定胡家岸引黄水闸属于平底淹没孔流流态。基于水闸上下游水位、闸孔开度、开发孔数、流量系数等,建立过闸流量水力学推算公式。利用历史观测数据,采用最小二乘法的方法拟合流量系数与闸孔相对开度的关系曲线,建立利用闸孔相对开度计算流量系数的数学公式。最后,通过对实测数据与计算结果进行比较,验证了计算方法的准确性。 相似文献
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驼峰堰是由三段圆弧曲线复合而成堰面的一种低堰,具有结构简单,整体稳定性和断面应力分布较好,堰体低,流量系数高,堰前不易淤积,且对地基要求较低,设计和施工相对简便等优点,因而,国内中小型工程采用较多。本文结合青海雪龙滩电站溢洪道挑流消能方案的试验研究,在几何比尺为1:40的模型上,对该工程进口段采用的驼峰堰特定体形的水力特性进行了详细的观测,并着重对自由溢流时流量系数随堰顶水头的变化规律,淹没流态判 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