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浅析水利水电工程沉沙池泥沙沉降计算方法 总被引:4,自引:1,他引:3
本文对沙早水电工程沉沙池设计中最常用的泥沙沉降计算方法,准静水沉降法和一度流超饱和输沙法,从公式结构上进行了一定的分析研究,结果表明,在一定条件下,准静水沉降法之计算公式是一度流超饱和输沙法(不考虑水流挟沙能力)的一种近似表达式,可用来估算沉沙池内含沙量变化。 相似文献
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文章采用RNG(重整化群)k-ε双方程紊流模型和简化的多相流Mixture(混合)模型,对浑水水力分离装置内水沙两相湍流场进行了数值模拟,得到浑水水力分离装置的柱体区、悬板区以及锥体区内含沙水流的平面速度矢量分布、含沙水流的紊动强度分布以及泥沙体积浓度分布。通过装置内清、浑水流场的计算结果,分析了泥沙的存在对装置内水流平均流速和紊动强度的影响,以及不同区域内影响水沙分离的主要作用力。研究结果表明泥沙的存在不会削弱水流的平均运动,但泥沙可有效地抑制水流的紊动扩散作用,有利于悬浮泥沙的沉降,装置内不同部位影响水沙分离的主要作用力不同,在锥体区和悬板区水沙分离主要依靠离心力,而在柱体主要依靠重力沉降。 相似文献
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一种新型矩形沉沙池已在新疆建设兵团大面积推广使用,这种沉沙池在进口增设了调流墙,在溢流堰上沿设置了溢流槽。从泥沙沉淀特性和经济性能两个方面对新型矩形沉沙池与传统沉沙池进行了比较。结果表明,新型矩形沉沙池的泥沙沉淀率比传统沉沙池提高了6%,出池含沙量由1.63 g/L降到了0.86 g/L,工程造价降低了20%左右,其泥沙处理效果和经济性更优,适宜在新疆地区农业节水灌溉中推广应用。 相似文献
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Hydrologically Based Environmental Flow Methods Applied to Rivers in the Maritime Provinces (Canada)
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The demand for water withdrawal continues to increase worldwide. These water withdrawals from rivers can affect fish habitat and aquatic life. As such, environmental flow assessment methods are used in order to protect rivers against excessive water withdrawals. The concept of environmental flow relates to the quantity of water required in rivers to sustain an acceptable level of living conditions for aquatic biota at various phases of their development. For many agencies, environmental flow methods are essential in environmental impact assessments and in the protection of important fisheries resources. The present study deals with the evaluation of hydrologically based environmental flow methods within the Maritime Province of Canada. In total, six hydrologically based environmental flow methods were compared using data from 52 hydrometric stations across the region. Some methods provided adequate environmental flow protection (e.g. 25% mean annual flow and Q50 flow duration method); however, other methods did not provide adequate flow protection (e.g. Q90 flow duration method and 7Q10 and 7Q2 low‐flow frequency). The 70% Q50 method provided adequate flow protection only under good baseflow conditions and should be applied with extreme caution. The present study shows the importance of the hydrologic flow regime, particularly as it pertains to the baseflow component, as a significant determinant in the level of instream flow protection. © 2014 Her Majesty the Queen in Right of Canada. River Research and Applications © 2014 John Wiley & Sons, Ltd. 相似文献
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AN APPROACH IN MODELING TWO-DIMENSIONAL PARTIALLY CAVITATING FLOW 总被引:10,自引:7,他引:3
1. INTRODUCTIONCavitation is a phenomenon that widely occurs in liquids. When the flow leads to the local pressure below the saturation vapor pressure of water (the fluid medium, in our research), usually incipient cavitation firstly occurs on the solid b… 相似文献
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The natural flow paradigm (NFP) emphasizes the need to partially or fully maintain or restore the range of natural intra‐ and interannual variation of hydrologic regimes to protect native biodiversity and the evolutionary potential of aquatic, riparian and wetland ecosystems. Based on our studies of natural and managed flow regimes in New Zealand, we do not believe that all components of the natural flow regime are necessary to achieve the objectives of the NFP, either partially or fully, because many aquatic species have very flexible niches and life‐history requirements (i.e. there is ‘ecological redundancy’). Obviously, maintaining the natural flow regime will maintain the hydrologic and hydraulic conditions necessary for sustaining natural ecosystems. However, if there is adequate knowledge of what ‘values’ need to be maintained in a waterway, and the aspects of the flow regime that are required to maintain those values are also known, then regimes can be designed that target these requirements and thus optimize conditions for the ‘values’. We believe that an assessment of ecosystem requirements using information on river processes together with habitat requirements and life‐history strategies of biota can achieve the best balance between resource use and sustaining ecosystem function and value, and show examples where changes to natural flow regimes have maintained, or even improved, instream values in some New Zealand rivers. We caution that simple flow‐based rules, such as those that might be developed under the NFP, could be unnecessarily restrictive on multiple use of water in New Zealand while, at the same time, preclude the opportunity for enhancement of key ecosystem values in many waterways. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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本文介绍了混合流的概念,结合某一中型水库的试验,观测了混合流在抬高尾水时的下游流态。流速分布的变化规律以及对消能效果的影响。从而说明了低水头泄洪建筑物利用挑流消能有更多的可能性。 相似文献
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Liu Fa-quan 《水动力学研究与进展(B辑)》1999,(1)
1.INTRODUCTIONInthedesignofanovertoppedrock--filldam,oneofthemajortasksistodecidethesizeofthedownstreamprotection.Theovertoppedrock--filldamismadeofporousmedia,thereforethewaterwillpenetrateintothedamfromtheupperfaceandemergeoutofitfromthelowerpart,whileitflowsoverthedam.Hence,theprotectionissubjectedtotheactionofboththeoverflowandtheseepageflow,andneitherofthemcanbenegligible.Inthiscase,theflowfieldconsistsoftwoparts:theopenflowandtheseepageflow,whichhavedifferentproperties.Infact,forthe… 相似文献
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本文利用计算机可视化的方法对直槽流动的数值模拟结果进行了处理,得到了若干组显示涡量场和涡管运动变化的计算机动画,通过对这些直观的动画进行分析,发现了直槽流动失稳的一些现象,对于流动稳定性的研究具有一定的参考价值。 相似文献