嘉峪关水文站堰闸推流探讨

针对讨赖河嘉峪关水文站堰闸推流方法做了详细的分析论证。根据实测资料,绘制出堰闸前水头h_u—流量系数C_1、溢洪坝上游水头h_u—流量系数C_1及闸门开启高度与闸前水头之比e/h_u—孔流流量系数M等关系曲线图,找出堰闸出流规律,确定出流流量计算公式,推求自由式堰流和孔流流量系数及溢洪坝流量系数,并率定得出经验公式。在Excel电子表格中编制出孔流流量计算模块,完成推流计算,解决了复杂的测验和整编过程。     

基于流态辨识的弧形闸门过流计算

过闸流量的精确计算是实现调水工程闸门自动控制、调度运行系统仿真和工程适时、适量供水的重要前提。在闸后收缩断面为低弗劳德数(约Fr1.7)的淹没孔流条件下,现有弧形闸门过流计算的经验系数模型和量纲分析模型流量预测误差较大。基于已有试验数据分析,研究提出了闸孔淹没出流的高Fr区和低Fr区的流态辨识参数——综合能耗系数Er,定义为相对开度e/H和潜流比Xr之和,即Er=e/H+Xr,相应的流态辨识方法为:Er1为高Fr的部分淹没孔流,Er≥1为低Fr的完全淹没孔流。针对闸孔出流的不同流态,即自由孔流、部分淹没孔流和完全淹没孔流,分别建立相应的流量计算模型,采用最小二乘辨识进行模型参数的估计,实例验证表明流态辨识模型整体的预测精度较高,80%预测流量的相对误差|EQ|±10%,且EQ近似呈正态分布。本文提出的流态辨识方法和计算模型为过闸流量的精确计算提供了新的思路和方法。     

实用堰式闸坝水力计算程序设计

在进行实用堰式闸坝的水力学计算或水库泄洪时闸门的开启调度中,常常遇到以下两类问题: 其一:已知泄流量、孔数、孔宽、上下游水位及堰顶高程等,求闸门的开启度; 其二:已知闸门的开度、孔数、孔宽、上下游水位及堰顶高程等,求孔流或堰流流量。根据闸门的开度e与上游堰上水深H之比小于或等于大于0.75,可分为孔流和堰流。     

堰闸孔流公式推算堰流流量应用分析

以总渠六垛南闸水文站流量推算为例,采用堰闸沉溺式孔流公式计算堰流流量,定线结果表明其三项检验合格,实测流量与计算流量的均方差达到二类精度标准,完全符合水文资料整编规范要求;与同类方法相比,该法具有定线方便、计算简单、便于估算等优点。     

刘家道口节制闸泄流曲线研究

根据刘家道口闸开闸泄水以来2008—2011年积累的实测水文资料,利用水工建筑物测流SL20—1992规范公式对刘家道口闸泄流量进行分析计算,分别计算包括行近流速的过闸流量和不计行近流速的过闸流量,两者进行对比,得出考虑行近流速水头计算的过闸流量偏大,结合实际情况考虑李庄闸回水影响得出了比较适合刘家道口节制闸运行情况下的堰流、孔流流量系数计算公式。结合ADCP实测流量点据,绘出了刘家道口节制闸自由式孔、堰流泄流曲线,淹没式孔、堰流泄流曲线。     

堰闸自由孔流流量计算的一种间接方法

以自由孔流、自由堰流同流量闸上游水头差为参数，并根据水力学原理推导出孔流上游水民其参数之间成直线关系，从而可和堰流公式推求孔流流量闸上游水头差为经实测验证，精度较高，为自由孔流流量推求提供一条间接计算途径。     

水闸测流孔 堰流分界点实验分析

利用水闸测流量 ,因省时、省力、精确 ,倍受广大水文职工的青睐 ,测流实验就是要率定孔流系数线和堰流系数线 ,进而推求过闸流量。率定工作中的难点 ,就是确定孔、堰流分界点 ,分界点确定的准确性关系到水闸测流的精确度。以下从 4个方面对孔、堰流分界点的确定作一些探讨。1　标准堰型的孔堰流分界点　　堰流与孔流是 2种不同的水流现象 ,堰流不受闸门控制影响 ,水面线为一条光滑的降落曲线 ,而孔流受闸门控制影响 ,闸门上、下游水面不连续 ,两者的水流特征及过水能力不同。对一个水闸在一定条件下属于堰流 ,在另外的条件下就变成孔流 ,这…     

定流量调度时三河闸开高确定方法研究

科学合理利用洪泽湖水资源,其主要口门三河闸须精准调度运行。研究定流量调度时三河闸 闸门开高的精准确定方法。采用规范确定的水闸出流公式,结合2004年至2016年流量实测资料和长期 调度运行实践,提出确定闸门开高的经验公式。重新率定三河闸淹没孔流、淹没堰流关系曲线,绘制三 河闸调度流量差－上游水位变幅值关系曲线和三河闸（中渡）流量－水位关系曲线,分析三河闸孔流和 堰流分界值确定方法,提出了定流量调度时确定三河闸闸门开高的方法。2016年测流数据表明,此方法 预测流量的最大绝对误差为5．74％,误差小于5％的概率达84％;可靠性较高,可用于三河闸精准控制。     

闸孔出流定线方法浅谈

万福闸淹没孔流历年来一直采用堰闸流量系数法推流,由于受到闸门开启高度和下游潮汐涨落影响,关系曲线点据下部密集,上部稀少,点据分布极不均匀。笔者通过对堰闸流量定线方法的简要综述,详细介绍堰闸流量系数法与堰闸过水平均流速法在万福闸孔流推流中的具体应用,并通过误差精度和相关关系的分析比较,判别出适合万福闸孔流推流的定线方法。     

引黄济青工程建设管理发展思考

<正>引黄济青工程是我国"七五"期间的重点工程,也是山东省自新中国成立以来已建成规模最大、距离最长的跨流域调水工程。工程自黄河打渔张闸引水,在渠首沉沙后,途经滨州、东营、潍坊、青岛,采用明渠输水方式输水至棘洪滩水库,渠道全长252.5 km。渠首引水流量41 m3/s,渠末输水流量23 m3/s。工程于1986年开工建设,1989年建成通水,至今已运行24年,     

Hydrologically Based Environmental Flow Methods Applied to Rivers in the Maritime Provinces (Canada)

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.     

AN APPROACH IN MODELING TWO-DIMENSIONAL PARTIALLY CAVITATING FLOW

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…     

Application of the ‘natural flow paradigm’ in a New Zealand context

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.     

台阶式溢流坝中小流量流态改善方式研究

台阶式溢流坝有显著的掺气效果和消能效果,目前在中小型工程中广泛应用。但是台阶式溢流坝在小流量浅水深的工况下,坝面上流态较差,呈现跌流或者过渡流态,容易形成水翅和水流跃离现象。为了解决上述问题,本文结合某工程通过水工模型试验研究对台阶起始端的体型进行优化,结果表明优化方案能够很好地改善较小流量时的过渡流态。     

中小型泄水工程利用附着混合流消能问题的探讨

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。     

无旋流研究

本文将变分法和流网相结合,从理论上证明了无旋流条件下流量达到极大值,并总结出流量达到极大值时,下游流动的两种表现形式:临界流和均速流。文中给出了下游流动分别为临界流和均速流两种情况下的7个实例。在无旋流条件下,应用本文的结果可以进行如下两种情况的计算:(1)利用求极大值来求流量;(2)当流量已知时,如果下游流动为临界流,则可求水深及流速;如下游流动为均速流,则可求流速等。     

均匀来流中振动圆柱尾迹涡结构的数值研究

本文从涡量流函数形式的N-S方程出发,对于不同的振动频率、振幅,首次数值研究了均匀来流中沿任意方向(参见图1,0°相似文献   

ON THE CALCULATION OF FLOW OVER AND THROUGH A ROCK-FILL DAM

1.INTRODUCTIONInthedesignofanovertoppedrock--filldam,oneofthemajortasksistodecidethesizeofthedownstreamprotection.Theovertoppedrock--filldamismadeofporousmedia,thereforethewaterwillpenetrateintothedamfromtheupperfaceandemergeoutofitfromthelowerpart,whileitflowsoverthedam.Hence,theprotectionissubjectedtotheactionofboththeoverflowandtheseepageflow,andneitherofthemcanbenegligible.Inthiscase,theflowfieldconsistsoftwoparts:theopenflowandtheseepageflow,whichhavedifferentproperties.Infact,forthe…     

低含沙水流运动特性综述

本文着重综述了清水水流、挟沙水流的流速分布动特性、能量间分配关系等流动现象的内部规律，并系统分析比较了它们的异同，文中还兼论了卡门常数。