陡坡隧洞不同进口形式的水力特性分析

为研究陡坡隧洞的泄流能力和洞内水流流态等水力特性与隧洞进口形式的关系,以某水电工程支流导流陡坡长隧洞为例,运用水力计算分析和模型试验验证的方法,分析比较了锐缘进口和曲线进口形式对陡坡隧洞泄流能力和流态的影响。研究表明:采用曲线进口形式可以提高泄流能力,降低围堰高程,但设计工况下洞内流态处于明满交替流状态,不利隧洞结构安全;采用锐缘进口形式,泄流能力有所降低,但可避免洞内出现明满交替流状态。综合比较认为,在围堰规模较小时,设计陡坡隧洞采用锐缘进口更为合理。     

多用途水工隧洞水力特性及运行方式研究

水利水电工程中的过水隧洞有导流洞、泄洪洞、放空洞以及发电引水洞等,它们各自具有一定的水流适用条件,对单一用途的水工隧洞,其洞内水流特性较容易把握。当由于技术、经济条件让一条隧洞具备多种用途时,隧洞将面临着不同运行阶段显著的水力差异性考验。结合某水利工程多用途水工隧洞水力模型试验,研究了集导流、泄洪、放空及发电引水等功能于一体的陡坡隧洞在不同运行阶段的相关水力特性。结果表明当作为泄洪隧洞在正常工况下运用时,隧洞进口前和洞内流态均较正常,洞内最小压力满足水工隧洞设计规程要求;当作为导流隧洞和放空洞运用时,隧洞进口在一定水流条件下会形成吸气型立轴漩涡,并在洞内形成形态不断变化且不断溃灭的气囊,在较长的洞段及较大的流量区间内,洞内还会出现明满交替流以及发电支洞岔管引起的明流冲击波、水流折冲等不良流态,上述水流现象会引发洞壁的有害振动或空蚀破坏。通过试验优化,并结合隧洞末端工作闸门的合理调度,提出了多用途水工隧洞的安全运行方式。     

水工隧洞流态问题研究

隧洞是常见的泄水建筑物,在水利工程中有着广泛的应用。清楚地了解隧洞的洞内流态随流量的变化是设计洞身尺寸和结构的依据,尤其是无压洞弯道段自由水面的波动、脉动压强变化规律的掌握更是关键。文章结合龙潭水库导流兼泄流放空隧洞水力学模型试验,对无压泄洪洞内弯道水流特性进行了全面深入的研究,同时对存在的无压隧洞弯道的高速水流问题提出工程解决方案。     

乌东德５号导流隧洞改建体型水力特性研究

乌东德水电站下闸蓄水期间利用５号导流隧洞过流,以满足坝下生态流量及水位衔接的要求。针对原导流洞体型有压段出口流速高的问题,提出了在导流洞有限的有压段范围内增设洞塞消能的方案。采用三维数值模拟技术对四种洞塞方案进行了研究,根据计算成果及生态流量要求确定采用两级洞塞方案。采用模型试验对两种两级洞塞方案的流态及压力进行了详细研究,结果表明:随着水位的增加,两种改建体型的导流洞有压段流态均从明流向满流转变,并在闸门段出现不稳定气囊。两级洞塞及延长方案的时均压力值及分布规律相似,脉动压力均波动剧烈且部分测点达到负压极值,延长方案泄水孔进口处脉动压力峰值略小。     

南水北调中线工程穿黄隧洞水力学试验研究

采用水工模型试验研究了南水北调中线穿黄隧洞两种布置方案的水力学问题，结果表明：虽然两个方案的过汉能力均满足设计要求，但由于方案Ｉ的控制闸设在隧洞进口，通过小流时量，因隧洞进口水位较低，进口处易发生跌流或洞内水跃；当通过大流量时，进口前有动的立轴游涡出现，气泡和漂浮物易被带进洞内，对隧洞的安全运行将产生不利影响。方案Ⅱ将控制船凤在隧洞出口，通过闸门调度，可以避免进口处产生不利流态；在闸墩上设置侧堰，     

苏洼龙水电站导流隧洞设计

苏洼龙水电站导流隧洞具有洞身断面尺寸大、运行时间长和泄流量大的特点。本文通过对导流隧洞洞身、进出口、堵头等方面的设计进行分析,为其它大中型导流隧洞的设计提供了参考与借鉴。     

施工期导流洞进口水流流态试验分析——以西沟水电站为例

西沟水电站位于地势险峻、水能资源丰富的黑龙江省黑河市,其施工导流采用断流围堰、隧洞导流的方式.对于导流洞入口的位置及形式,给出了两种方案,在对这两种方案的进口水流流态进行试验研究比较后进行了优化选择.     

变坡长隧洞明满流水力特性研究

明满流交替是长隧洞常遇到的不利水流流态,尤其是洞内截留气囊输移现象会对隧洞结构安全构成威胁。通过试验研究,阐述了变坡长导流隧洞洞内流态的演变过程,指出随着上游水位上升,洞内水流流态呈现由水跃转变为明满流交替、直至有压流的演变过程,分析了典型流态下隧洞的泄流能力,得到了明满流交替的流量系数介于无压流和有压流流量系数之间的结论。同时探讨了明满流交替过程的压力波动,发现明满流交替的压力波动持续时间较长、振幅较大,但压力峰值持续的时间很短,并且截留气囊可有效减缓隧洞底部压力波动。     

二滩水电站导流隧洞轴线布置优化

二滩水电站左、右岸导流隧洞沿线地质条件复杂，且处于高地应力区。根据抠纽建筑物的优化布置和新的基本资料，对初步设计选定的导流隧洞轴线进行了优化。优化后，洞线长度缩短，节省了土石方和洞挖开挖量，节省了混凝土量，使导流工期得到保证。优化方案的左岸导流隧洞进口不受金龙沟发生泥石流的影响．右岸导流隧洞轴线长度缩短且与软弱岩带走向接近正交，两洞的出口流态改善。     

鄂托克赛尔水库输水洞工程设计

鄂托克赛尔水库输水隧洞建于1988至1991年。施工阶段输水隧洞洞线布置方案较初步设计做了重大调整,改善了围岩条件,优化了水流流态。文中着重介绍输水隧洞洞线布置方案、进口布置、洞身断层与渗透处理方法。     

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。     

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   

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。     

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…     

直槽流动失稳过程数值模拟的可视化

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。