共查询到18条相似文献，搜索用时 156 毫秒
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SHEN Huanting Institute of Esturaine Coastal Research East China Normal University Shanghai China LI Jiufa Institute of Esturaine Coastal Research East China Normal University Shanghai China ZHU Huifang Institute of Esturaine Coastal Research East China Normal University Shanghai China HAN Mingbao Institute of Esturaine Coastal Research East China Normal University Shanghai China ZHOU Fugen 《国际泥沙研究》1992,(3)
The Changjiang River is characterized by the enormous volume of runoff and the great amount of sediment load with remarkable seasonal variation. The annual runoff sometimes is respondent to the amount of sediment load, and sometimes not. The amount of monthly sediment load after the month of the maximum runoff is larger than those before the month. The sediment concentration and net quantity of sediment transport in the vicinity of the river mouth varies greatly in time between the ebb and flood, spring and neap, and dry seasons and flood seasons. The three bifurcations also have differences in concentration and net quantity in space. Even in the same bifurcation they have differences in and out of the sand bar. At present, the North Channel is the main passage for water and sediment load emptying into the sea from the Changjiang River. More than 50 percent of the sediments from the river basin are deposited nearby the South Branch entrance and the main depositional area is situated in subaqueous delta off the South Channel. Between 122°30'E and 123°E is an important boundary for eastward sediment dispersion from which the suspended sediment are dispersed towards the east by south. 相似文献
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Measurements of coupled fluid and sediment motion over mobile sand dunes in a laboratory flume 总被引：1，自引：1，他引：0
The relationship between turbulent fluid motions and sediment particle motions over mobile sand dunes was investigated by using a laser Doppler velocimeter and an acoustic backscatter system in laboratory experiments performed at the USDA-ARS-National Sedimentation Laboratory. Profiles of acoustic backscatter from particles and at-a-point turbulence data were collected while translating both measurement devices downstream at the speed of mobile dune bedforms. The resulting data set was used to examine the frequency （recurrence frequency） at which the fluctuating backscatter and fluid velocity signals exceeded magnitude thresholds based on the standard deviation （σ） of the local velocity and the magnitude the acoustic signal resulting from backscatter from suspended particles. The slope of the downstream and vertical velocity recurrence frequencies generally indicated a gradually increasing recurrence time with increasing elevation. The recurrence frequency for acoustic backscatter data was not strongly variable with elevation. The closest correspondence between the recurrence frequencies of sediment backscatter and vertical velocities at the 1σ magnitude threshold was in a region defined by X/L〈0.4 and y〈6 cm. The downstream velocity was most closely related to backscatter in a small region at 0.4〈X/L〈0.8 and less than 3-4 cm from the bed. 相似文献
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RATIONAL BASIS FOR SUSPENDED SEDIMENT MODELING 总被引：1，自引：0，他引：1
Jianjun ZHOU Biniiang LIN Bingnan LIN Prof Dept. of Hydraulic Eng. Tsinghua University Beijing P.R. China Senior Lecturer School of Eng. Cardiff University Queen''''s Buildings P.O.Box Cardiff CF EW UK Dir. Emeritus China Inst. of Water Resources Hydropower Res. Formerly Chief of Sedimentation Panel for TGP Chairman Emeritus of Advising Council IRTCES P.O. Box. Beijing P.R. China 《国际泥沙研究》2003,18(3)
This paper presents a rational basis to model the transport of suspended sediment. The loose-boundary condition for 3D models and the adjustment coefficients for both the depth-integrated 2D and laterally integrated 1D models are treated comprehensively. A combination of Dirichlet and Neumann conditions is proposed as the loose-boundary condition. The adjustment coefficient for 2D models is obtained on the basis of the proposed boundary condition and analytical solutions developed for some simple cases of non-equilibrium transport of sediment in uniform flows. The adjustment coefficient for 1D models for natural rivers is further obtained from lateral integration. Comparisons with analytical solutions and a considerable amount of laboratory and prototype data show that mathematical models developed along the proposed line of attack would well simulate the transport of suspended sediment in practical problems. 相似文献
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This paper illustrates how the acoustic Doppler current profiler （ADCP） and single-beam echo-sounder （SBES） recordings can be used for the calibration of existing software to assist in generalizing the morphodynamic processes in large rivers at key sites such as bifi.trcations and confluences. Calibration of the MIKE21C numerical model by the Danish Hydraulic Institute at the 25-km-long reach of Lower Paran~ near Rosario （Argentina） is presented. This reach includes two downstream confluences and two bifurcations. The model simulates a 2-D depth-averaged flow velocity and the related sediment fluxes to predict the bifurcation morphodynamics that affects the Paranh waterway. To investigate the river channel bathymetry, roughness, flow discharge allocation at bifurcations, suspended sediment concentration and grain size distributions, several instruments were used. These instruments included two ADCPs by Teledyne RDI working at frequencies of 600 and 1,200 kHz, a Sontek ADCP working at a frequency of 1,000 kHz and a SBES. The method to assess suspended sediment concentration and grain size distributions has been previously described. This paper focuses primarily on investigating dune morphology （by means of SBES depth measurements） and friction velocity （by means of ADCP profiling） to determine the river channel bed-roughness. The 2-D model results agree with observed values of bed-roughness, flow velocity and suspended sediment concentration distributions at the investigated sections, known data of water slope and total load of bed sediment are in good agreement with model results. 相似文献
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Evaluation of total load sediment transport formulas using ANN 总被引：2，自引：0，他引：2
The calculated results from various sediment transport formulas often differ from each other and from measured data. Some parameters in the sediment transport formulas are more effective than others to estimate total sediment load. In this study, an Artificial Neural Network （ANN） model is trained using four dominant parameters of sediment transport formulas. ANN models are able to reveal hidden laws of natural phenomena such as sediment transport process. The results of ANN and some total bed material load sediment transport formulas have been compared to indicate the importance of variables which can be used in developing sediment transport formulas. To train ANN, average flow velocity, water surface slopes, average flow depth, and median particle diameter are used as dominant parameters to estimate total bed material load. Two hundreds and fifty samples are used to train the ANN model. Twenty-four sets of field data not used in the training nor calibration of ANN are used to compare or verify the accuracy of ANN and some well-known total bed material load formulas. The test results show that the ANN model developed in this study using minimum number of dominant factors is a reliable and uncomplicated method to predict total sediment transport rate or total bed material load transport rate. Results show that the accuracy of formulas in descending order are those by Yang （1973）, Laursen （1958）, Engelund and Hansen （1972）, Ackers and White （1973）, and Toffaleti （1969）. These results are similar to those made by ASCE （1982） based on laboratory and field data not used in this paper. Study results also show that the formulas based on physical laws of sediment transport, like those formulas that were developed based on power concept, are more accurate than other formulas for estimating total bed material sediment load in rivers. 相似文献
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Liton Kumar SARKER M. Monowar HOSSAIN M. Anisul HAQUE 《国际泥沙研究》2007,22(3):169-179
Experiments on initiation of motion of different fractions of non-uniform sediment mixtures are reported. Four sediment mixes and reference transport method to define the threshold of bed particle movement are used in this analysis. Factors controlling the initiation of motion are analyzed. It is found that relative size of different grains with respect to a median size greatly affects the initiation of movement. The incipient motion of non-uniform sediment is very much dependent on the absolute size for coarser fractions. Considering the factors controlling the initiation of motion the experimental data sets along with the other available data yield a new relationship for the calculation of critical shear stress of non-uniform sediments. A set of equations have found that all the data points fall into a single line for the finer and for coarser fractions. 相似文献
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Point velocity and suspended sediment concentration measurements are used to calculate the total sediment discharge in sand-bed rivers.Calculations with the Series Expansion of the Modified Einstein Point Procedure(SEMEPP) depend on grain diameter d_s and settling velocity ω,flow depth h,shear velocity u*,and sampling depth h_p.This procedure extends the applicability of the Modified Einstein Procedure(MEP) by using point sediment concentration and velocity measurements.This procedure is tested using the laboratory data from Coleman,and field measurements from the Enoree,Middle Rio Grande and Mississippi Rivers.Based on 801 point measurements over 124 verticals at flow depths ranging from 0.17 m to 33.5 m and sediment concentrations less than 0.1 kg L~(-1),the accuracy of the calculations depends on u*/ω and h_p/d_s.Point measurement techniques like SEMEPP are well-suited when u*/ω 5 where at least 60%of the total sediment load is measured when 90%of the flow depth is sampled.The determination of sediment discharge from point measurements is most accurate in deep rivers when h_p/d_s 10.000.and u*/ω10.Point measurements are not well-suited for shallow rivers and laboratory flumes where h 0.5 m and when u*/ω 2. 相似文献
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Relationship between bed shear stress and suspended sediment concentration:annular flume experiments
In this study,annular flume experiments were carried out,using the sediment samples collected from the lower part of the inter-tidal zone at Xiaoyangkou,Jiangsu coast,China.The Ariathurai-Partheniades equation was used to determine the bed shear stress,by evaluating variations in the suspended sediment concentration within the water column.The derived relation between the bed shear stress and suspended sediment concentration shows that,at various stages of seabed erosion, suspended sediment concentration increases rapidly when the flow velocity is increased,but the pattern of change in the bed shear stress does not follow suit.At low concentrations,bed shear stress initially increases markedly with increasing flow velocity.However,when the concentration reaches an apparently critical level around 0.55 kg m"3,the rate of change in the bed shear stress abruptly slows down,or becomes almost constant,in response to further increases in the flow velocity.Results of experiments indicate that,from a critical level onward,suspended sediment concentration has a strong influence on the bed shear stress. 相似文献
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Sediment fingerprinting in fluvial systems： review of tracers,sediment sources and mixing models 总被引：3，自引：0，他引：3
Suspended sediments in fluvial systems originate from a myriad of diffuse and point sources, with the relative contribution from each source varying over time and space. The process of sediment fingerprinting focuses on developing methods that enable discrete sediment sources to be identified from a composite sample of suspended material. This review identifies existing methodological steps for sediment fingerprinting including fluvial and source sampling, and critically compares biogeochemical and physical tracers used in fingerprinting studies. Implications of applying different mixing models to the same source data are explored using data from 41 catchments across Europe, Africa, Australia, Asia, and North and South America. The application of seven commonly used mixing models to two case studies from the US （North Fork Broad River watershed） and France （Bldone watershed） with local and global （genetic algorithm） optimization methods identified all outputs remained in the acceptable range of error defined by the original authors. We propose future sediment fingerprinting studies use models that combine the best explanatory parameters provided by the modified Collins （using correction factors） and Hughes （relying on iterations involving all data, and not only their mean values） models with optimization using genetic algorithms to best predict the relative contribution of sediment sources to fluvial systems. 相似文献
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Ricardo N. Szupiany Cecilia Lopez Weibel Massimo Guerrero Francisco Latosinski Molly Wood Lucas Dominguez Ruben Kevin Oberg 《地球表面变化过程与地形》2019,44(6):1295-1308
Quantifying sediment flux within rivers is a challenge for many disciplines due, mainly, to difficulties inherent to traditional sediment sampling methods. These methods are operationally complex, high cost, and high risk. Additionally, the resulting data provide a low spatial and temporal resolution estimate of the total sediment flux, which has impeded advances in the understanding of the hydro-geomorphic characteristics of rivers. Acoustic technologies have been recognized as a leading tool for increasing the resolution of sediment data by relating their echo intensity level measurements to suspended sediment. Further effort is required to robustly test and develop these techniques across a wide range of conditions found in natural river systems. This article aims to evaluate the application of acoustic inversion techniques using commercially available, down-looking acoustic Doppler current profilers (ADCPs) in quantifying suspended sediment in a large sand bed river with varying bi-modal particle size distributions, wash load and suspended-sand ratios, and water stages. To achieve this objective, suspended sediment was physically sampled along the Paraná River, Argentina, under various hydro-sedimentological regimes. Two ADCPs emitting different sound frequencies were used to simultaneously profile echo intensity level within the water column. Using the sonar equation, calibrations were determined between suspended-sand concentrations and acoustic backscatter to solve the inverse problem. The study also analyzed the roles played by each term of the sonar equation, such as ADCP frequency, power supply, instrument constants, and particle size distributions typically found in sand bed rivers, on sediment attenuation and backscatter. Calibrations were successfully developed between corrected backscatter and suspended-sand concentrations for all sites and ADCP frequencies, resulting in mean suspended-sand concentration estimates within about 40% of the mean sampled concentrations. Noise values, calculated using the sonar equation and sediment sample characteristics, were fairly constant across evaluations, suggesting that they could be applied to other sand bed rivers. © 2018 John Wiley & Sons, Ltd. 相似文献
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Haoming FAN Qiangguo CAI Chengjiu GUO Tieliang WANG 《国际泥沙研究》2006,21(3):209-219
1 INTRODUCTION The particle size of sediment eroded from basins can provide basic information about erosion processes (Meyer et al., 1980), which can be divided into sheet wash sediment processes on hill slopes and fluvial sediment processes in rivers. In… 相似文献
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1 INTRODUCTION Alluvial streams generally have permeable bed sediments that can admit significant pore water flows. Steady flow of surface water over bed roughness features such as sand waves or pools and riffles can then drive water flow into and out of the shallow subsurface. This is often termed hyporheic exchange, and the subsurface region where mixing between stream and ground waters occurs is the hyporheic zone (Hynes, 1983). The hyporheic zone has been shown to be a critical com… 相似文献
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ZHOU Prof Dr. -Ing. Sedimentation Division Department of Hydraulic Engineering Tsinghua University Beijing J. China. SPORK Research Engineer Dip.-Ing. Institute of Hydraulic Engineering Water Resources Developmot Aachen V. University 《国际泥沙研究》1997,(3)
I.INTRODUCTIONSuspendedsedimenttransportissaidbeinanycaseaphenomenaofa3Dprocess.Becauseofthelimitationsincomputercapacity,mostoftheexistingmodelstreateditasatlvoorevenonedimensionalproblem.WiththerapidadvancesofcomputersinbothCPUandmemorycapacity,andbecauseoftheavailabilityof3Dmodelsforturbulentflowsimulationsinpracticalapplications,thefully3Dsimulationofsuspendedsedimentbecomesafeasibleandurgenttaskforhydraulicengineers.TheprocessofsuspendedsedimenttransportisdescribedbytheadVection-d… 相似文献
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LIU Shuguang CHALOV R.S WU Dandan LI Congxian Postdoctor Research Fellow Key Laboratory of Marine Geology Tongji University Shanghai China & Researcher State Key Laboratory of Estuarine Coastal Research Shanghai China Professo 《国际泥沙研究》2000,(3)
I INTRODUCTIONThe volume and regime of sediment load are the most important factors, which are responsible for theformation, direction and deformation rate of the river channels. Despite the long history of study anddevelopment of sediment load calculation methodology, there are still numerous problems that remain tobe solved such as river pattern and sediment movement and so on (Wang et al, 1997).In this respect, the comparative analysis of sediment load and river channel processes of la… 相似文献
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Ray Kostaschuk Dan Shugar Jim Best Dan Parsons Stuart Lane Rich Hardy Oscar Orfeo 《地球表面变化过程与地形》2009,34(12):1605-1611
Field data from the Rio Paraná, Argentina, are used to examine patterns of suspended sediment transport over a sand dune. Measurements of three‐dimensional velocity are made with an acoustic Doppler current profiler whilst suspended sediment concentration and particle size have been quantified using a laser in situ sediment scattering transmissometer. Suspended sediment concentration and streamwise and vertical sediment flux are highest close to the bed, with an upward vertical flux over the stoss side of the dune and downward flux over the lee side. Suspended sediment concentrations are higher over the crest compared with the trough and suspended sediment is coarsest near the bed. About 17% of the suspended‐load transported over the crest is deposited in the lee side before it reaches the trough. Most of this deposited sand is coarser sediment that originates close to the bed over the crest, a result consistent with simulations based on the model of Mohrig and Smith (Water Resources Research 1996; 32: 3207–3217) for the excursion lengths of sediment dispersed in the lee side of a dune. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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The magnitude and processes of solute acquisition by dilute meltwater in contact with suspended sediment in the channelized component of the hydroglacial system have been investigated through a suite of controlled laboratory experiments. Constrained by field data from Haut Glacier d'Arolla, Valais, Switzerland the effects of the water to rock ratio, particle size, crushing, repeated wetting and the availability of protons on the rate of solute acquisition are demonstrated. These ‘free-drift’ experiments suggest that the rock flour is extremely geochemically reactive and that dilute quickflow waters are certain to acquire solute from suspended sediment. These data have important implications for hydrological interpretations based on the solute content of glacial meltwater, mixing model calculations, geochemical denudation rates and solute provenance studies. 相似文献