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三维水流河床变形数学模型 总被引:4,自引:3,他引:1
本文针对三维水流所具有的紊动各向异性,不规则边界及自由表面和动床问题。采用修正的K-ε模型封闭Reynolds方程作为紊流控制方程;引入通度概念处理不规则边界;引用VOF法追踪自由表面;根据冲刷过程的物理特性推得冲刷坑的发展规律并用前人公式及试验资料验证。最后,作为例子就南水北调中线方案名河渡槽河段的流场和河床变形进行数值模拟,给出了一些工程上有用的结果。 相似文献
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一种新的三维孔口水流数值解法 总被引:3,自引:0,他引:3
本文提出了一种新的三维孔口水流数值解法,在势流假设下,通过调和变换,将具有复杂边界形状的物理空间(x,y,z),转换到规则空间(ξ,η,β)上,用显式迭代方法解出势函数,进而可求出三维流场的流速分布、压力分布、自由表面位置和泄流量.这种解法不但解决了三维求解中遇到的网格结点布置的困难,而且占用计算机内存少,可在微机上实现.算例表明,该算法有很好的收敛性,计算结果与试验值较好地吻合. 相似文献
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三维过坝水流是一种具有自由表面的临界流动,即使在势流假设下,因其非线性强,数值求解时也会遇到较大困难,目前尚未见到有效势流解法。本文提出一种正交调和变换法,可方便地采用笔者曾提出的自由表面位移理论,同步解出待定的自由表面位置和未知能头(或流量)。算例表明,该三维过坝水流的计算方法是成功的,计算结果与试验值吻合较好。 相似文献
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《黑龙江水利科技》2019,(11)
文章综合漂移通量模型、卷气模型和紊流模型,三维数值模拟了某实际导流工程下泄水流局部掺气的影响。针对复杂地形条件的导流工程采用CATIA软件建立三维几何模型。然后对溢洪道水流局部掺气条件下的导流工程整体流场利用Tru VOF水流自由表面追踪法、卷气模块及RNG k-ε紊流模型进行了计算,从而揭示了水力参数压强、水位和流态的分布规律,通过对比分析数值模拟结果和物理模型试验验证了模型的可靠性。研究表明:数值模拟能够较为准确的计算上游围堰设计高程,在导流工程流场计算中具有较强的科学性和有效性;在三维流场中引入卷气模块较好的揭示了掺气范围、水流掺气浓度、压强及流速分布特征,可为其他类似工程的计算模拟提供一定参考价值。 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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宽顶堰水流数值模拟分析 总被引:1,自引:0,他引:1
本文利用紊流模型模拟了带有曲线自由表面的宽顶堰流的紊流流场,采用VOF法来确定自由表面,采用气液两相流计算模型对宽顶堰流场进行了数值模拟,计算结果与试验数据较为吻合.模拟结果表明,数值模拟是作为研究水利工程中带有自由表面的水流结构的一个强有力的工具,其结果对物理试验也是一个很好的补充. 相似文献
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工程中液面波动的数值模拟 总被引:11,自引:2,他引:9
本文研究数值模拟含有自由表面的三维非定常流动的表面波动情况。运用部分单元法的概念成功地 各种复杂形状的边界以及复杂的边界条件和流场内部的障碍物,运用VOF方法踪自由液面。 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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Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river. 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