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1.
哈岸英  吴腾  陈刚 《水利学报》2012,43(1):10-14
通过理论分析与数值计算,研究了冲积河流漫滩水流水力因子的变化特性。结果表明,断面平均流速在漫滩瞬间迅速减小,然后逐渐增大;断面综合动能修正系数、动量修正系数均随水深而缓慢增加,在漫滩瞬间迅速增大,随即快速减小。根据漫滩水流水力因子沿水深的变化特性,提出采用断面横向平均流速为判别因子以定量划分复式断面的滩与槽。此外,文中将其应用于黄河下游漫滩水流的水沙数值模拟,其结果与实际情况符合较好。  相似文献   

2.
宽窄复式河道水流运动特性的试验研究   总被引:2,自引:0,他引:2  
在分析水槽试验资料的基础上,首次对宽窄复式河道的滩槽过流能力、断面平均流速、垂线流速及横向分布等水流运动特性进行了研究.研究结果表明,宽窄复式河道的主槽流量随着滩槽宽度比的增大而减小,滩地流量随着滩槽宽度比的增大而增大;水流发生漫滩之后,随着水深的增加,主槽流速先减小后增加,滩地流速不断增加,二者的变化幅度与滩槽宽度比有关;在大部分区域内垂线流速偏离对数分布,主槽一般偏小,滩地偏大;垂线平均流速沿横向分布与一般复式河道相似,但滩槽流速差别减小.  相似文献   

3.
漫滩水流水沙运动规律的研究   总被引:7,自引:2,他引:5  
吉祖稳  胡春宏 《水利学报》1998,29(9):0001-0007
本文根据漫滩水流的运动特点,将漫滩水流的复式断面分为主槽平衡区、滩槽交互区、滩地平衡区及边壁区等4个区,并给出了各区宽度的经验公式.根据滩槽交互区垂线流速分布的变化特点,提出了附加尾流函数的对数流速分布公式.在简化水流运动方程和泥沙扩散方程的基础上,对滩槽交互区内垂线平均流速及含沙量沿横向分布进行了理论分析,提出了反映滩槽水流动量交换强度的横向涡量粘性系数及横向扩散系数的表达式,得到了漫滩水流垂线平均流速及含沙量沿横向分布的解析解,并与实测资料吻合较好。  相似文献   

4.
黄河下游斜河形成机理分析   总被引:1,自引:1,他引:0  
研究了不同条件下概化复式断面的水沙分布规律,定量分析了黄河下游河道斜河产生的机理,结果表明:复式断面滩、槽流速和挟沙力存在较大差异,易引起横向冲淤变化,在一定程度上促进了斜河的发展;河道水、沙量的剧烈变化均能引起河道水深和水面比降的快速变化,导致河道断面流速和挟沙力的显著增大或减小,引起主槽的大量淤积,改变原有的流路形成斜河;对于束窄河段,由于河道断面宽窄相间,且存在滩洲,因此当局部淤积较大时,易引起主流的偏离并形成斜河.  相似文献   

5.
复式河槽的洪水漫滩后,滩槽水流相互作用,在滩槽交界处形成动量交换,若直接采用曼宁公式进行水力计算将产生很大误差。应用CES(Conveyance Estimation System)模型首先计算了不同复式河槽的垂线平均流速,并结合英国科学工程研究理事会洪水水槽设备(SERC-FCF)的试验资料进行了验证,进而分析了不同形态复式河槽的水流特性;然后通过对比分析CES模型与经验方法(湿周修正法、断面分割法)和理论方法(谢汉祥法、刘沛清法、河槽协同度法)计算流量时的精度,论证了该模型在复式河槽水力计算中的优越性。结果表明,由CES模型计算的断面垂线平均流速分布符合复式河槽的水流特性且与实测资料吻合良好,较之其他模型方法,该模型能适用于任意形态复式河槽的流量计算且精度较高。  相似文献   

6.
滩槽复式断面水流特性的试验研究   总被引:2,自引:0,他引:2       下载免费PDF全文
采用水槽试验研究复式断面水流流速的横向分布特征、边界剪切应力变化规律以及水力参数对断面过流能力的影响,并得出了滩槽流量分配计算式。  相似文献   

7.
明渠断面水流流速与边界剪切应力横向分布模型   总被引:1,自引:0,他引:1       下载免费PDF全文
天然河流的横断面多为由主槽和漫滩组成的复式断面,水流在这种断面中比在单一断面中受到更多因素影响,流态也更加复杂。通过将明渠横断面上微元体在水流方向的N-S控制方程沿水深积分,得出描述垂线平均流速和边界剪切应力横向分布的模型,并通过对实验数据的验证,确定了模型的实用性。  相似文献   

8.
黄河下游河道滩地横比降较大,大洪水时漫滩行洪,滩槽水沙交换剧烈,考虑滩地横比降的影响既符合实际又具有较强的理论意义。漫滩水流流速是研究河流横断面形态调整的重要水力参数,目前对其二维解析解的研究均未考虑滩地横比降的影响。在前人研究基础上,推导出考虑滩地横比降影响的漫滩水流运动方程,拟合无因次横向涡黏性系数计算公式,求解滩地垂线平均流速横向分布的解析解,并利用实测资料进行验证。验证结果表明该解析解可以用来计算滩地垂线平均流速横向分布。  相似文献   

9.
基于等效阻力的植被化复式河道流速分布研究   总被引:1,自引:0,他引:1  
天然河道中许多都是具有主槽和滩地的复式河槽,水流漫滩以后,复式河槽的水流结构发生复杂的变化.而天然河道漫滩上常常生长着各种植物,水中植被的存在增加了河床的阻力,如何确定流速分布和流量十分重要.本文基于植被作用下水流阻力的等效平衡原理,提出刚性植被等效附加阻力系数以及植被等效综合阻力系数的计算方法.通过运用SKM方法计算植被作用下的复式河槽垂线平均流速的横向分布,结果表明,本文提出的植被等效综合阻力系数的计算方法是可行的,能较好地确定植被作用下的复式河道垂线平均流速的横向分布.  相似文献   

10.
漫滩挟沙水流流速横向分布研究   总被引:4,自引:0,他引:4  
在建立漫滩挟沙水流掺混区横向涡粘性系数表达式的基础上,根据水深平均的水流运动方程,得到掺混区流速横向分布公式,经验证,该公式与实测资料基本上吻合。  相似文献   

11.
The transport of water and sediment from rivers to adjacent floodplains helps generate complex floodplain, wetland, and riparian ecosystems. However, riverside levees restrict lateral connectivity of water and sediment during flood pulses, making the re‐introduction of floodplain hydrogeomorphic processes through intentional levee breaching and removal an emerging floodplain restoration practice. Repeated topographic observations from levee breach sites along the lower Cosumnes River (USA) indicated that breach architecture influences floodplain and channel hydrogeomorphic processes. Where narrow breaches (<75 m) open onto graded floodplains, archetypal crevasse splays developed along a single dominant flowpath, with floodplain erosion in near‐bank areas and lobate splay deposition in distal floodplain regions. Narrow breaches opening into excavated floodplain channels promoted both transverse advection and turbulent diffusion of sediment into the floodplain channel, facilitating near‐bank deposition and potential breach closure. Wide breaches (>250 m) enabled multiple modes of water and sediment transport onto graded floodplains. Advective sediment transport along multiple flow paths generated overlapping crevasse splays, while turbulent diffusion promoted the formation of lateral levees through large wood and sediment accumulation in near‐bank areas. Channel incision (>2 m) upstream from a wide levee breach suggests that large flow diversions through such breaches can generate water surface drawdown during flooding, resulting in localized flow acceleration and upstream channel incision. Understanding variable hydrogeomorphic responses to levee breach architecture will help restoration managers design breaches that maximize desired floodplain topographic change while also minimizing potential undesirable consequences such as levee breach closure or channel incision.  相似文献   

12.
河滩种树对行洪影响试验研究   总被引:32,自引:2,他引:30  
对宽滩和窄滩河槽的过流能力以及滩地种树的漫滩水流水力特性进行了研究表明:像珠江三角洲网河这样的窄滩复式河槽,滩地种树对水位的影响不大,也不会影响滩地的槽蓄滞洪作用,但种树使滩地水流归槽,主槽流速增大;滩地种树的利和弊及对行洪的影响是多方面的,应视具体情况分析。  相似文献   

13.
HYDRAULICS OF COMPOUND CHANNEL WITH VEGETATED FLOODPLAINS   总被引:13,自引:7,他引:6  
1. INTRODUCTIONThe Pearl River delta is often subject to typhoons and heavy rainfalls. Big waves generated by typhoons cause scouring, even collapsing and breaching of river embankments. Facts have proved that the effectiveness for wind and ship wave prot…  相似文献   

14.
This paper presents the results of an experimental study on the influences of floodplain impermeable groynes on flow structure,velocity,and water depth around the groyne(s).A wooden symmetrical compound channel was used.Groyne models with three different groyne relative lengths,0.5,0.75,and 1.0,were used on one floodplain with single and series arrangements.Analysis of the experimental results using the measured flow velocity and water depth values showed that flow structure,velocity,and water depth mainly depend on groyne relative length and the relative distance between series groynes.The flow velocity at the main channel eenterline increased by about 40%,60%,and 85%,and in other parts on the horizontal plane at the floodplain mid-water depth by about 75%,125%,and 175% of its original value in cases of one-side floodplain groyne(s)with relative lengths of 0.5,0.75,and 1.0,respectively.The effective distance between two groynes in series arrangement ranges from 3 to 4 times the groyne length.Using an impermeable groyne with a large relative length in river floodplains increases the generation of eddy and roller zones downstream of the groyne,leading to more scouring and deposition.To avoid that,the groyne relative length must be kept below half the floodplain width.  相似文献   

15.
水流运动特性受边界的影响较大,由于复式渠槽特有的几何特征和边界条件,当发生漫滩流时,水流结构比较复杂,水流特性和泥沙输移规律均不同于单一渠槽。分别对顺直和弯曲复式渠槽漫滩情况下的流速分布、剪切力分布、水流阻力及泥沙输移特性进行归纳和分析。从复式断面形态、滩槽交互区动量交换、推移质泥沙运动特性以及自然因素条件对水沙输移特性的影响4个方面,对复式渠槽水沙输移特性的研究趋势进行了展望。  相似文献   

16.
顺直型与宽窄型复式河道水沙分布规律的比较   总被引:1,自引:0,他引:1  
本文在总结水槽试验资料的基础上.对顺直型及宽窄相间型复式河道的过流能力、流速及含沙量分布特性进行了比较分析。研究结果表明,两种复式河道的水沙分布具有一定的相似性,但也存在着较大的差别,并对其产生的原困进行了初步探讨。此外,通过比较滩槽流速比及滩槽流量比可以知道.宽窄复式河道的滩槽动量交换较顺直复式河道强烈。  相似文献   

17.
The dynamic nature of alluvial floodplain rivers is a function of flow and sediment regimes interacting with the physiographic features and vegetation cover of the landscape. During seasonal inundation, the flood pulse forms a ‘moving littoral’ that traverses the plain, increasing productivity and enhancing connectivity. The range of spatio-temporal connectivity between different biotopes, coupled with variable levels of natural disturbance, determine successional patterns and habitat heterogeneity that are responsible for maintaining the ecological integrity of floodplain river systems. Flow regulation by dams, often compounded by other modifications such as levee construction, normally results in reduced connectivity and altered successional trajectories in downstream reaches. Flood peaks are typically reduced by river regulation, which reduces the frequency and extent of floodplain inundation. A reduction in channel-forming flows reduces channel migration, an important phenomenon in maintaining high levels of habitat diversity across floodplains. The seasonal timing of floods may be shifted by flow regulation, with major ramifications for aquatic and terrestrial biota. Truncation of sediment transport may result in channel degradation for many kilometres downstream from a dam. Deepening of the channel lowers the water-table, which affects riparian vegetation dynamics and reduces the effective base level of tributaries, which results in rejuvenation and erosion. Ecological integrity in floodplain rivers is based in part on a diversity of water bodies with differing degrees of connectivity with the main river channel. Collectively, these water bodies occupy a wide range of successional stages, thereby forming a mosaic of habitat patches across the floodplain, This diversity is maintained by a balance between the trend toward terrestrialization and flow disturbances that renew connectivity and reset successional sequences. To counter the influence of river regulation, restoration efforts should focus on reestablishing dynamic connectivity between the channel and floodplain water bodies.  相似文献   

18.
漫滩水流特征综述   总被引:1,自引:0,他引:1  
水流漫滩后,主槽流速减小,滩地流速增大,但主槽流速大,滩地流速小,滩槽之间流速的差别使滩槽交界面上产生剪切力,两部分水流在交界面上发生动量交换,滩槽交界面产生大量次生流、旋涡,并伴随着大量的能量耗散。滩槽的边壁切应力分布不均,尤其是滩槽交界面处。流速和切应力不均匀分布导致了主槽水流含沙量降低,滩地水流含沙量升高。从五方面对漫滩水流特征的研究成果作简要概述。  相似文献   

19.
Aquatic vegetation plays an important role in the flow structure of open channels and thus changes the fate and the transport of sediment. This article proposes a three-dimensional turbulence model by introducing vegetation density and drag force into the control equations of water flow in the presence of vegetation. The model was used to calculate the impacts of submerged vegetation on the vertical profiles of longitudinal flow velocities, the changes of the depth-averaged flow velocities in a compound channel with emergent vegetation in the floodplain, the removal of suspended sediment from the channels by emergent vegetation, and the bed changes around and in a vegetated island. Numerical investigations show that aquatic vegetation retards flow in the vegetation zone, reduces the sediment transport capacity, and contributes to erosion on both sides of the vegetated island. Calculated results agree well with experimental results.  相似文献   

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