共查询到19条相似文献，搜索用时 961 毫秒
1.
根据大江截流期间监测,收集到的成果资料,对长江水全部改由导流明渠下泄、所观测到的大江围堰戗堤进占对导流明渠分流及流速流态的变化,河床冲淤及淤积量纵、横向分面进行了阐述,得到了该河段水流及冲淤变化的一般性规律。 相似文献
2.
三峡工程大江截流龙口与导流明渠水文水力学计算和检验 总被引：1，自引：0，他引：1
三峡工程大江截流是世界上截流流量最大,水深最大和抛投强度最大的截流工程。鉴于大江截流及二期围堰的重要性及技术复杂性,对上游围堰龙口,导流明渠进行了水文水力学分析计算,得到了各级坝址流量下明渠分流比,龙口落差,流速等水力要素成果,并进行了实时校验,结果表明计算值与原型观测较为一致。 相似文献
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万里长江第一坝——葛洲坝水利枢纽于1981年元月4日胜利完成大江截流,这在我国水利水电建设史上是一项空前未有的壮举。在这次大江截流的整个过程中,长办水文局组织了全江300人的水文测验队伍参加各项水文测验工作。全面准确地搜集了整个截流过程中的截流河段水位、龙口流速、落差、二江分流量、坝区流速流态和水下地形资料,其中实测得龙口最大流速为为7米/秒。确保截流的胜利,及时、准确、主动地提供了有关水文数据,起到了参谋和耳目的作用。目前他们正集中力量对资料进行整理分析和进行工作总结。 相似文献
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截流水文泥沙监测中几个关键技术的研究与实践 总被引：3，自引：0，他引：3
基于三峡工程大江截流水文泥沙监测除常规水文要素外,要求监测围堰龙口和导流明渠附近水体多维水文要素的时间和空间动态变化,因此应尽可能应用相关科技的最新成果和一切先进经验,成熟的技术方法和设备。本文介绍了其中无人立尺接测水位ＡＤＣＰ测流,龙口测验,ＧＰＳ和数据传输等几个关键部位,关键技术室内外研究实验及现场率定校正的情况,实践证明,这些技术的研究与应用,为截流水文泥沙监测打下了基础,并发挥了重要作用。 相似文献
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三峡工程大江截流水文泥沙监测规划 总被引：1，自引：0，他引：1
鉴于三峡工程大江截流是一项复杂的系统工程,具有水深大,流量大,抛投量大和截流期不断航等显著特点。水文泥沙监测作为其重要的组成部分,监测导流与截流过程中水流泥沙和水下地形的变化,为截流设计优化,调整施工方案与措施等提供科学的决策依据,同时也为导流明渠分流与通航,围堰度汛,截流水力学试验研究及水文预报,水文分析计算等提供水文原型观测资料。本文介绍了水文泥沙监测的目的、任务和水文数据采集,传输,处理与信 相似文献
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以浙江省温州市瓯江江堤外移工程为例,应用二维潮流数学模型研究了堤线外移的不同工程方案对城市防洪的影响。该模型能够模拟瓯江与楠溪江交汇引起的复杂水流运动,以及多岛屿对水流流场的影响。验证计算表明,计算的潮位及18条垂线流速及断面流量过程与实测值吻合较好,误差均小于10%。因堤线外移的部分大多位于河道岸线的凹囊,适当外移可使河道岸线更趋平顺。100年一遇洪水时,瓯江大桥至鱼旗山堤线外移曲线方案1与直线方案2分别使屿头山-梅岙河段最高潮位壅高0.03～0.04m及0.04～0.08m。多年平均流量450m3/s时,方案2使塔山至鱼旗山断面垂线平均流速增加6%～22%,工程段以外河段流速变化较小;方案1缩窄的河宽和拦截过水面积明显小于方案2,相应引起流速变化也较小。 相似文献
7.
三峡工程大江截流的水文技术 总被引：2，自引：0，他引：2
鉴于三峡工程大江截流水深大，流量大，工期紧，特别是截流过程中要考虑不断航因素，因此，在大江截流和二期围堰阶段的施工进程中，应充分考虑到各方面的因素，尽可能采取一切减少大江截流和二期围堰施工难度的手段和措施，其中水文测验，水文气象预报，河道观测，水文分析与计算和水力学计算等水文工作则是为顺利实施高质量大江截流的重要条件。 相似文献
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对长江上游枯季降雨洪水特性和分期设计洪水进行了分析计算。结果表明：１月下旬至２月中旬降水量和流量虽均接近最小,但从二期围堰施工的紧迫性和围堰度汛的重要性考虑,大江截流时间宜早不宜晚。 相似文献
10.
为研究生产堤溃口横向展宽过程的发展规律,以黄河下游生产堤土体为材料,开展概化模型试验,分析溃口处水深、流速、流量以及溃口宽度的变化。试验结果显示,溃口横向展宽的机理主要表现为水流冲刷堤身下层土体伴随上层悬臂土体发生绕轴崩塌;随着溃口展宽,堤前水深持续下降但下降速率逐渐减小,溃口流速呈先增大后减小的趋势,流速峰值约为1.1 m/s;随着主槽流量增加,溃口宽度发展至0.7 m时,溃口的水深、泄流流量、流速、展宽速率均有所增加。基于对溃口展宽的影响因素分析,提出溃口横向展宽速率的计算关系式,计算溃口展宽过程与实测值符合较好。研究结果不仅有助于生产堤展宽机理及发展规律的研究,还可为数学模型的建立与验证提供参考资料。 相似文献
11.
JOSÉ ANTONIO CONSTANTINE THOMAS DUNNE HERVÉ PIÉGAY G. MATHIAS KONDOLF 《Sedimentology》2010,57(2):389-407
Differences in the nature and quantity of sediment filling oxbow lakes have significant implications for the evolution of meandering rivers and the development of floodplains, influencing rates of meander migration and the valley width over which migration takes place. In an effort to identify the controls on the alluviation of oxbow lakes by coarse bed material, this study examined the sedimentary records stored within oxbow lakes of the Sacramento River of California, USA, and found that the volume of gravel in storage correlated negatively with the diversion angle separating flow between the river channel and the entrance into each lake. A method was devised for estimating the original channel bathymetry of the studied lakes and for modelling the hydraulic and sediment‐transport effects of the diversion angle within channels recently abandoned by meander cut‐off. The diversion angle determines the width of a flow separation within the abandoned‐channel entrance, reducing the discharge diverted from the river channel and thus limiting the ability of the abandoned channel to transport bed material. Aggradation rates are faster within entrances to abandoned channels with high diversion angles, resulting in the rapid isolation of lakes that store only a small volume of coarse‐grained sediment. Aggradation rates are slower within channel entrances where diversion angles are low, resulting in the slow transitioning of such channels into oxbow lakes with a larger and more extensive accumulation of coarse‐grained sediment. These findings compare well with observations in other natural settings and the mechanism which is described for the control of the diversion may explain why some oxbow lakes remain as open‐water environments for centuries, whereas others are filled completely within decades of cut‐off. 相似文献
12.
Flow and sediment dynamics in a low sinuosity, braided river: Calamus River, Nebraska Sandhills 总被引：1，自引：0，他引：1
The interaction between channel geometry, flow, sediment transport and deposition associated with a midstream island was studied in a braided to meandering reach of the Calamus River, Nebraska Sandhills. Hydraulic and sediment transport measurements were made over a large discharge range using equipment operated from catwalk bridges. The relatively low sinuosity channel on the right-hand side of the island carries over 70% of the water discharge at high flow stages and 50–60% at low flow stages. As a result, mean velocity, depth, bed shear stress and sediment transport rate tend to be greater here than in the more strongly curved left-hand channel. The loci of maximum flow velocity, depth and bed shear stress are near the centre of the channel upstream of the island, but then split and move towards the outer banks of both channels downstream. Variations in these loci depend on the flow stage. Topographically induced across-stream flows are generally stronger than the weak, curvature-induced secondary circulations. Water surface topography is controlled mainly by centrifugal accelerations and local changes in downstream flow velocity. The averaged water surface slope of the study reach varies very little with discharge, having values between 0·00075 and 0·00090. As bed shear stress generally varies in a similar way to mean velocity, friction coefficients vary little, normally being in the range 0·07–0·13. These values are similar to those in straight channels with sandy dune-covered beds. Bedload is moved mainly as dunes at all flow stages. Grain size is mainly medium sand with coarse sand moved in thalwegs adjacent to the cut banks, and with fine sand at the downstream end of the island. These patterns of flow velocity, depth, water surface topography, bed shear stress, bedload transport rate and mean grain size can be accurately predicted using theoretical models of flow, bed topography and sediment transport rate in single river bends, applied separately to the left and right channels. During high flow stages deposition occurs persistently near the downstream end of the island, and cut banks are eroded. Otherwise, erosion and deposition occurs only locally within the channel as discharge varies. Abandonment and filling of a strongly curved channel segment may occur by migration of an upstream bar into the channel entrance at a high flow stage. 相似文献
13.
灌区分水口多为直角, 附近普遍存在冲刷、淤积及结构破坏现象。天然河流分、汇流多为锐角, 为探索非直角分水口区域明渠水流紊动特性, 以30°分水角明渠为研究对象, 采用声学多普勒点式流速仪测量各断面上的三维瞬时流速, 分析典型断面上的时均流速、环流强度、紊动强度、紊动能和床面剪切应力分布规律。试验结果显示: 分水口处水流横向流速沿渠宽方向变化较大, 易形成环流, 导致局部冲淤现象明显; 靠近口门侧水流紊动强度变化剧烈且分布无规律, 最大值出现在口门上唇断面; 分水口处下层水体紊动能明显大于上层水体, 紊动能较大值多集中在口门附近; 口门断面下唇附近床面剪切应力较大, 易出现冲刷侵蚀, 破坏渠道稳定; 与直角分水口相比, 分水角为30°时, 泥沙颗粒不易进入侧渠道, 水流对渠底及边壁侵蚀速率较低。研究结果可为灌区渠系设计及运行提供参考。 相似文献
14.
The water column flow velocity of 36 river sections in the river reach between Hankou (Wuhan) and Wuxue of the middle-lower
Changjiang River. Their cross sectional distribution patterns in relation to the river channel morphologies were examined
by using ship-mounted ADCP (Acoustic Doppler Current Profiler) instrument. The results indicate four (I-VI) types of river
channel morphology associated flow patterns: I—laterally deepening riverbed topographic pattern; II—symmetrical to asymmetrical
riverbed topographic pattern; III—relative flat riverbed topographic pattern, and IV—sandbar supported riverbed topographic
pattern. All these correspond to the different patterns of flow velocity distribution. The maximum flow velocity is usually
related to the deeper water depth, but irregular water column distribution of flow current velocity results often from the
vortices’ current associated with river knots. Deeper river water depth is usually identified in the river reach located slightly
downstream to the river knot, where faster flow velocity occurs. Downward change in flow velocity fits semi-log law, showing
an exponential decreasing flow current with the maximum flow velocity near the water surface. However, in the river reach
near the river knots, the water column distribution of flow current velocity does not fit the semi-log law, showing the irregular
flow current pattern. This study, in context of river catchment management, highlights the controls of riverbed morphology
to the flow current structure, which will shed light on the post study of Three Gorges damming in 2009. 相似文献
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基于能量守恒原理,通过实体模型试验的方法,对河流发生弯曲的机理进行了探讨。研究认为,河流具有弯曲的自然属性,其弯曲程度主要取决于水流能量的大小,与流量、比降有很大关系;河流发生弯曲是水流为补偿能量损失得以保持运动而形成的一种自然造床过程,河流在运动过程中,通过弯曲形成上游壅水,增加势能,使下游比降相对增大,动能得以增加,从而保持河段内的水沙输移达到相对平衡,此即"动能自补偿"的弯曲机理;河流弯曲程度与需要补偿的动能多少有关,河段上下断面的动能差越大,河段弯曲系数就越大。"动能自补偿"的机理得到了实验室观测结果的验证和野外原型定位观测资料的佐证。 相似文献
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为探讨砾石群对河道生物栖息地自然化改造效果,以江西金沙溪河段为例,采用文献调研和数值模拟的方法,选择鲢鱼为目标物种,耦合河段的平面二维水动力及栖息地模拟,研究了砾石群布置对裁弯河道生物栖息地的影响特性及自然化改造效果。结果表明:裁弯河道鲢鱼栖息地加权可用面积（AWU）明显减少,弗劳德数在其主流线附近增大,剪切速度值由原河道的横向梯度分布转变为均匀分布;砾石群对裁弯河道生物栖息地的自然化改造效果显著,其中河道凹岸高密度布置方式使鲢鱼栖息地可用面积百分率（APU）由裁弯河道的9.20%增长至15.06%,砾石群下游附近水流的弗劳德数由裁弯河道的0.13~0.68骤降至0~0.15,砾石群下游区域形成低速水流区,为鲢鱼在大流量河道中提供了良好的庇护场所。 相似文献
18.
Study on hydraulic geometry can reveal the response of river systems to basin attributes, and the trends in channel change. Based on 35 years of data collected at 10 hydrological stations (cross-sections), the hydraulic geometry relations between cross-sectional variables and discharge were established, and the derived parameters were analyzed. The channel behavior of the mountainous bedrock reach (from riverhead to Xunhua cross-section) and the alluvial reach (from Xunhua to Toudaoguai cross-sections) differed significantly over the past decades in response to dramatic water and sediment changes. The hydraulic geometry quasi-equilibrium was achieved through equally adjusting water depth and flow velocity in the mountainous bedrock reach; while primarily through flow velocity in the alluvial reach. The change rate of river width with varying discharge was relatively small in the whole upper Yellow River. Compared with the lower Yellow River and other rivers in the world, both similarity and differences existed, indicating the general adjustment direction of hydraulic quasi-equilibrium and also the importance of considering other influencing factors in hydraulic geometry studies. In addition, dams played an important role in affecting the changes of hydraulic geometry exponents. 相似文献