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水流挟沙力的统计理论计算方法及其应用 总被引:1,自引:0,他引:1
将水流挟沙力作为二维问题处理是水流挟沙力研究的重要方向,采用非均匀沙水流挟沙力的统计理论方法,根据泥沙状态概率和有效床沙级配,推导了悬移质挟沙力、推移质输沙率和推悬比统计理论公式,利用黄河下游水沙资料对公式进行验证,并与半经验悬移质挟沙力和推移质输沙率公式进行计算对比验算。计算结果表明,采用统计理论公式计算中、低含沙水流非均匀沙悬移质挟沙力较为准确,统计理论方法计算的推悬比较为稳定,黄河下游底悬比在0.06~0.11之间变化,可以采用统计理论方法的推悬比公式计算黄河下游的漏测底沙量。 相似文献
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为解决现有的弯道悬移质横向输沙公式形式复杂、不便使用的问题,对Odgaard线性环流流速公式进行了简化,同时,以简化的环流流速公式和Laursen悬移质含沙量公式为基础,推导了弯道悬移质横向输沙率公式。公式验证结果表明:①简化后的线性环流流速公式形式简单,与实测资料符合较好;②推导得到的弯道悬移质横向输沙率公式变量较少且形式简单,在无高精度计算弯道悬沙横向输移的要求下,可用于实际工程的近似计算;③弯道环流引起的下部输沙量始终大于上部的输沙量。 相似文献
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挟沙水流的运动机理和输沙能力 总被引:2,自引:0,他引:2
惠遇甲 《水动力学研究与进展(A辑)》1996,11(2):133-149
本文是作者和一些同志近年来所进行挟沙水流的水流和泥沙运动机理和输沙能力研究成果的概括。内容包括:把挟沙水流运动视为统一体的观点;悬移质流速分布、浓度分布以及悬移质输沙率计算模式的讨论;作为推移质运动主要运动形式的颗粒跃移的运动机理以及对于Bagnold推移质输沙率公式的修正等 相似文献
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水库下游冲刷的数值模拟—模型的构造 总被引:2,自引:0,他引:2
由于水库下游冲刷过程中悬移质与推移质、推移质与河床质、河床质与悬移质交换机理及床沙粗化机理的复杂性,使得研究水库下游冲刷数学模型的难度较大。 为了研究水库下游冲刷、河床演变问题及由此而引起的对防洪、航运等造成的影响,本文建立了一维全沙数学模型,模型考虑了非均匀悬移质不饱和输移、非均匀沙推移质输移及床沙级配的调整。文中考虑了冲刷过程中挟沙能力的沿程调整,挟沙能力包括以下三个方面,即悬移质中细颗粒部分从累计效果看不参予与床沙交换(冲泻质),这部分泥沙全部计入挟沙能力;悬移质的粗颗粒部分落淤到床面与床沙交换后部分地计入挟沙能力;床沙中可悬浮部分从床面冲起后部分地计入挟沙能力。非均匀沙推移质输沙率公式考虑了床沙运动的随机性及床沙粗化对输沙率的影响。床沙级配的调整采用CARICHAR混合层模型。对计算中经常遇到的关键性问题提出了处理方法。 相似文献
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非均匀沙推移质输沙率及其级配计算 总被引:14,自引:0,他引:14
本文根据水流功率理论,导出了非均匀沙推移质输沙率公式,并考虑了床沙运动的随机性及床面粗化对输沙率的影响;提出了推移质级配计算的公式。由非均匀推移质输沙率及其级配计算公式的计算值与作者、Samaga、Gilbert试验值及长江新厂(二)站、美国东汊河实测值吻合较好,并且能够用于均匀沙的推移质输沙率计算,具有广泛的通用性。 相似文献
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非均匀推移质瞬时输沙率试验研究 总被引:2,自引:1,他引:1
推移质输沙率是泥沙运动力学的重要内容。目前,推移质输沙率的研究大多集中于时均输沙率,对瞬时输沙率的研究则相对较少。首先,介绍了Ballio提出的均匀沙瞬时输沙率的计算方法,对其进行推导得到非均匀沙瞬时输沙率计算公式;其次,通过非均匀沙水槽试验中得到不同颗粒泥沙的瞬时运动速度,代入改进的Ballio输沙率公式中,计算得到瞬时输沙率;然后,采用定义方法计算瞬时推移质输沙率,并与Ballio方法进行比较,结果表明两种方法得到的推移质瞬时输沙率较为接近,说明采用改进的Ballio方法计算非均匀推移质瞬时输沙率是可行的。同时,通过大量试验,揭示了非均匀推移质瞬时输沙率在时间上不稳定性、在空间上不均匀性以及运动过程中间歇性等特性。 相似文献
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对爱因斯坦均匀沙推移质输沙率公式修正的研究 总被引:2,自引:0,他引:2
本文讨论了爱因斯坦均匀沙推移质输沙率公式推导中对冲刷概率及泥沙冲刷交换时间的处理推求。笔者按流速的概率密度为正态分布及以此推导得出的上举力的概率密度分布,分别推导得出冲刷概率P的表达式,并提出了泥沙冲刷交换时间t的关系式,最后推导得出了新的输沙率公式。修正公式与试验点群比原公式在更广的范围内比较一致,可作为计算推移质总输沙率的定量公式,并可作为进一步研究非均匀沙水流挟沙力的基础。 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