共查询到18条相似文献，搜索用时 125 毫秒
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在前人研究成果的基础上,根据挟沙水流任一粒径组泥沙在输移过程中质量守恒原理,建立了一维非恒定挟沙水流悬移质泥沙和床沙交换基本方程;通过引入平衡冲淤物粒径的概念,建立了河床处于淤积与冲刷时冲淤物粒径的计算公式,并提出了一套完整的一维非恒定挟沙水流悬移质泥沙和床沙交换计算方法。将该成果引入黄河下游一维扩展泥沙数学模型中,采用黄河下游1977年高含沙洪水与1999年汛后至2002年汛前冲刷系列进行了验证。结果表明,该方法能较好地模拟悬沙与床沙的交换过程,克服分组挟沙力方法的缺陷,使得非均匀沙计算理论上更加完善,应用上更加方便。 相似文献
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应用作者提出的动床阻力、非均匀沙挟沙力、床沙交换调正及滩槽水沙交换等关系与新的不平衡输沙等初步经验关系,建立了黄河下游及水库河床变形计算一维数学模型。经1960年～1988年共28年实测水沙资料的验证计算,结果与实际基本符合。该模型的特点是可预报各种水流及河床边界条件下的动床阻力;可同时计算确定混合沙中各粒径组的推移质、悬移质挟沙力、含沙浓度垂线分布及上滩水流含沙量;能较好地反映浑水上滩淤积减沙使主槽减淤增冲的实际情况;能够基本反映泥沙多来多排及高含沙水流的冲淤特性;能综合反映出来水流量、含沙量及级配的调节变化产生的输沙冲淤差别。应用该模型计算黄河小浪底水库库区及下游河道的冲淤,成果比较合理。 相似文献
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为研究潮汐河道不同区段在流域来沙减少条件下的冲淤响应机制,以长江澄通河段为例,根据水动力特性将其划分为江阴—天生港和天生港—徐六泾两段,结合1950—2014年的水沙资料及2005—2014年的地形资料,比较两段冲淤对流域减沙的响应差异。结果表明:上游江阴—天生港段对流域减沙敏感,较快地由淤积转为冲刷;下游天生港—徐六泾段1998—2004年期间受洪季平均径流流量减小、潮汐顶托作用相对增大的影响,冲刷速率为减小趋势,2004年以后受洪季平均径流流量增大、潮汐顶托作用相对减小及流域来沙持续减少的共同影响,冲刷速率为增大趋势。使得潮汐动力对天生港—徐六泾段由促淤变为促冲的临界洪季平均径流流量为36 000 m3/s,该径流流量也是使得潮汐顶托作用在江阴—天生港段由不显著变为显著的临界流量。目前,流域减沙已加剧澄通河段整体的冲刷。 相似文献
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小浪底水库运行后, 坝下游分组悬沙输移特点发生改变, 不同河段冲淤过程有所差别。基于1999—2018年坝下游实测水沙资料及固定淤积断面地形数据, 分析汛期分组悬沙输移的沿程调整特点, 建立分组悬沙输移及河床边界条件双重影响下不同河段河床累计冲淤量的计算关系。分析结果表明: ①汛期各组沙输沙率远小于蓄水前, 且中沙输沙率降幅最大, 在各水文断面平均降幅为85%;沿程上细沙输沙率基本不恢复, 而中沙和粗沙恢复距离分别到利津及艾山。②坝下游河床持续冲刷, 各河段河床组成均发生不同程度的粗化; 在拦沙后期(2007—2018年), 游荡段和过渡段床沙中细沙和中沙占比不足5%, 对悬沙几乎无补给作用, 而弯曲段床沙对中沙仍有一定的补给能力。③下游各河段以冲刷下切为主, 但调整幅度不同, 故对水流的约束能力有所差异。建立了各河段累计冲淤量与前期河相系数及进口断面分组来沙系数的经验关系, 并采用2019年下游水沙数据对公式进行了初步验证, 公式能合理反映断面形态与分组悬沙输移对河床累计冲淤过程的影响。 相似文献
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针对渤海湾曹妃甸海域波浪、潮流、泥沙及海床演变特点,应用波流共同作用下二维泥沙数学模型研究港区开发方案。2006年冬季和夏季大、小潮潮流泥沙验证表明,该海域潮位及15条同步垂线流速、流向、含沙量过程的计算值与实测值吻合良好,并进行了矿石码头港池前沿海域在潮流与波浪共同作用下悬沙引起的冲淤验证,计算的冲淤厚度及其分布趋势与实测值比较接近。在此基础上,研究了曹妃甸前岛后陆的港区围垦方案对水动力环境的影响问题,包括该工程引起的曹妃甸甸头以南深槽、老龙沟深槽及各港池的流速变化及底床的冲淤变形等。 相似文献
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采用浑水控制方程,建立了基于耦合解法的一维非恒定非均匀沙数学模型,用于模拟高含沙洪水演进时的河床冲淤过程.然后采用黄河下游游荡段1977年7—8月实测高含沙洪水资料对该模型进行率定,基于水沙耦合解法的各水文断面流量、总含沙量及分组含沙量的计算过程与实测过程符合更好,计算的沿程最高水位及累计河段冲淤量与实测值也较为符合.最后还采用2004年8月高含沙洪水资料对该模型进行了验证.模型率定及验证计算结果表明,采用一维水沙耦合模型计算高含沙洪水过程,能取得较高的精度. 相似文献
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Loïc Guézennec Robert Lafite Jean-Paul Dupont Robert Meyer Dominique Boust 《Estuaries and Coasts》1999,22(3):717-727
The effects of fortnightly, semidiurnal, and quaterdiurnal lunar tidal cycles on suspended particle concentrations in the tidal freshwater zone of the Seine macrotidal estuary were studied during periods of medium to low freshwater flow. Long-term records of turbidity show semidiurnal and spring-neap erosion-sedimentation cycles. During spring tide, the rise in low tide levels in the upper estuary leads to storage of water in the upper estuary. This increases residence time of water and suspended particulate matter (SPM). During spring tide periods, significant tidal pumping, measured by flux calculations, prevents SPM transit to the middle estuary which is characterized by the turbidity maximum zone. On a long-term basis, this tidal pumping allows marine particles to move upstream for several tens of kilometers into the upper estuary. At the end of the spring tide period, when the concentrations of suspended particulate matter are at their peak values and the low-tide level drops, the transport of suspended particulate matter to the middle estuary reaches its highest point. This period of maximum turbidity is of short duration because a significant amount of the SPM settles during neap tide. The particles, which settle under these conditions, are trapped in the upper estuary and cannot be moved to the zone of maximum turbidity until the next spring tide. From the upper estuary to the zone of maximum turbidity, particulate transport is generated by pulses at the start of the spring-neap tide transition period. 相似文献
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A three-dimensional, intratidal sediment transport model is developed for the estuarine turbidity maximum (ETM) in the upper
Chesapeake Bay. The model considers three particle size classes, including the fine class mostly in suspension in the water
column, the medium class alternately suspended and deposited by tidal currents, and the coarse size suspended only during
the times of relatively high energy events. Based on the results of a box model, depth-limited erosion with continuous deposition
is employed for the medium and coarse classes by varying the critical shear stress for erosion as a function of eroded mass.
For the fine class, mutually exclusive erosion and deposition is employed with a small constant value for the critical shear
stresses for erosion and deposition to assure quick erosion of recently deposited fine particles but without allowing further
erosion of consolidated bed sediments. The model is run to simulate the annual condition in 1996, and the model generally
gives a reasonable reproduction of the observed characteristics of the ETM relative to the salt limit and tidal phase. The
model results for 1996 are analyzed to study the characteristics of the ETM along the main channel of the upper bay in intertidal
and intratidal time scales. Under a low flow condition, local erosion/deposition and bottom horizontal flux convergence are
the main processes responsible for the formation of the ETM, with the settling flux confining the ETM to the bottom water.
Under a high flow condition, a distinctive ETM is formed by strong convergence of the downstream flux of sediments eroded
from the upstream of the null zone and the upstream flux of sediments settled at the downstream of the null zone. Intratidal
variation of the ETM is mainly controlled by erosion and the tidal transport of eroded sediments for a low flow condition.
Under the direct influence of a high flow event, the ETM is mainly formed by erosion during ebbing tidal current strengthened
by large freshwater discharge and by convergence of ebbing freshwater discharge and flooding tidal current. During the rebounding
stage of a high flow event, intratidal variations are mainly controlled by tidal asymmetry caused by the interaction between
tidal currents, gravitational circulation, and stratification. 相似文献
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Studies on the water and suspended matter concentration dynamics were performed for the summer and autumn periods in Kruglaya
Bay, Chupa Inlet (Karelian Coast, the White Sea). The tidal cycle appeared as the major factor defining the water salinity,
temperature, and suspended matter concentration. The water temperature and suspended matter concentration increased during
low tide, and the opposite pattern was observed for water salinity; all the processes were true for both surface and bottom
water layers. Therefore, we conclude that major bulk of the allochtonous suspended matter is carried into the sea by the ebb
stream. 相似文献
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辽东湾北部浅海区泥沙输送及其沉积特征 总被引：16，自引：1，他引：16
根据实测资料，本文定量分析了辽东湾北部泥沙输送及其分布，并对辽河三角洲沉积区划作了初步讨论。研究表明本区泥沙以纵向搬运为特征。双台子河以西来沙和辽河西水道入海泥沙是区域东部拦门沙体和浅滩发育的主导因素。汛季大潮期，泥沙自西向东运移落淤在河口及毗邻浅水域；小潮期，泥沙除向东扩散外，大部泥沙向海方搬运。调查区可划分六个现代沉积作用区，即潮坪沉积区、辽河水下三角洲细粒沉积区、河口沙洲沉积区、波浪潮流冲蚀沉积区、河口冲积沉积区以及潮汐水道沉积区。 相似文献
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Temporal and spatial variation in intertidal sedimentation rates 总被引：2，自引：0，他引：2
P. A. CARLING 《Sedimentology》1982,29(1):17-23
Sediment deposition and erosion rates are reported for an intertidal zone in the Burry Inlet, South Wales. Measured deposition rates over the salt marsh are compared with deposition rates calculated from observed suspended sediment concentrations. Notably, it is concluded that residual turbulence at slack water should not be discounted when calculating deposition rates. Grain-size distributions of suspended sediments over the marsh surface, during flood and ebb tides, contrast with the grain-size distribution of deposited marsh sediments, the latter being significantly coarser. These data in conjunction with mass budget calculations are used to relate total annual deposition and sediment supply by tidal action during settled meteorological periods. The analysis suggests that episodic storm-induced sediment transport is probably an important mechanism for introducing coarse sediment on to the marsh surface. Finally, it is noted that seasonal reworking of the sandy non-cohesive sediments may be related to variations in the intensity of wave-breaking throughout the year. 相似文献
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基于多沙河流"多来多排"输沙基本公式,建立了考虑上站来沙量、前期累计淤积量、临界输沙水量及干支流泥沙粒径影响的输沙量一般表达式。进而根据黄河内蒙古河段1953—2010年实测水沙资料,得到了内蒙古巴彦高勒—头道拐全河段及巴彦高勒—三湖河口和三湖河口—头道拐分河段的年输沙量公式,并根据输沙率法采用建立的输沙量公式计算了各河段1953—2010年的逐年冲淤量。选取三湖河口—头道拐河段的计算结果分析表明,在输沙基本公式基础上增加前期累计淤积量、临界输沙水量及干支流泥沙粒径参数,所得公式计算的年冲淤量与实测值之间的相关系数R2由基本公式的0.41依次提高到0.50、0.75和0.80,说明在基本公式基础上进一步考虑这些参数的必要性。此外,全河及分河段输沙公式计算所得输沙量及各河段冲淤量和累计淤积量与实测值的符合程度均较好,表明建立的输沙公式能够用于不同水沙条件下的输沙量和冲淤量计算,可为分析内蒙古河段的输沙特性和长期淤积趋势提供参考。 相似文献