CALCULATION MODELS FOR THE SUSPENDED SEDIMENT TRANSPORT RATE

The calculation accuracy of the suspended sediment transport rate relies on that ofthe vertical distribution of the particle concentration,the particle velocity distribution and thereference concentration.In view of the limitations of the previons formulas for both the velocityand the concentration distributions,general expressions are introduced to the calculation of sus-pended sediment transport rate.Based on these analyses,a simple and practical calculation modelis given in the present paper.     

VERIFICATION AND COMPARISON OF FORMULAS FOR BED LOAD TRANSPORT

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｂｅｄｌｏａｄｔｒａｎｓｐｏｒｔｈａｓｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙｓｔｕｄｉｅｄｉｎｔｈｅｐａｓｔｆｅｗｄｅｃａｄｅｓａｎｄｍａｎｙｆｏｒｍｕｌａｓｆｏｒｐｒｅｄｉｃｔｉｎｇｂｅｄｌｏａｄｔｒａｎｓｐｏｒｔｒａｔｅｈａｖｅｂｅｅｎｐｒｅｓｅｎｔｅｄ(Ｅｉｎｓｔｅｉｎ 1950 ;Ｍｅｙｅｒ Ｐｅｔｅｒ 194 8;Ｂａｇｎｏｌｄ 1973;Ｅｎｇｅｌｕｎｄ 1976;Ｙａｌｉｎ 1972 ;Ｓａｍａｇａ 1986;ａｎｄＫａｒｉｍ 1998) .Ｗｈｅｎａｐｐｌｉｅｄｔｏｓｔｒｅａｍｓｗｉｔｈｐａｒｔｉａｌ…     

STUDY ON TOTAL SEDIMENT TRANSPORT BY FLOW

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＦｏｒｎａｔｕｒａｌｒｉｖｅｒｓｗｉｔｈｒｉｃｈｓｅｄｉｍｅｎｔ ,ｔｈｅｍｏｖｅ ｍｅｎｔｆｏｒｍｓｏｆｓｅｄｉｍｅｎｔｗｉｔｈｄｉｆｆｅｒｅｎｔｄｉａｍｅｔｅｒｓａｒｅｃｏｍｐｌｅｔｅｌｙｄｉｆｆｅｒｅｎｔｕｎｄｅｒｔｈｅａｃｔｉｏｎｏｆｆｌｏｗ .Ｇｅｎｅｒａｌｌｙｓｐｅａｋｉｎｇ ,ｔｈｅｒｅｍａｙａｐｐｅａｒｔｈｒｅｅｆｏｒｍｓｓｉｍｕｌｔａｎｅｏｕｓｌｙ ;ｓｕｓｐｅｎｄｅｄｌｏａｄ ,ｄｅｎｓｉｔｙｃｕｒｒｅｎｔａｎｄｂｅｄｌｏａｄ .Ｗｈｅｎａｄａｍｉｓｃｏｎｓｔ…     

A MATHEMATICAL MODEL FOR UNSTEADY SEDIMENT TRANSPORT IN NINGXIA REACH OF THE YELLOW RIVER

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＮｉｎｇｘｉａｉｓｌｏｃａｔｅｄｉｎｔｈｅｗｅｓｔｅｒｎｐａｒｔｏｆＣｈｉｎａ .ＴｈｅＹｅｌｌｏｗＲｉｖｅｒｐｌａｙｓａｎｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｔｈｅｄｅｖｅｌ ｏｐｍｅｎｔｏｆＮｉｎｇｘｉａ’ｓｅｃｏｎｏｍｙａｎｄｐｏｌｉｔｉｃｓ,ｂｕｔｉｔａｌｓｏｂｒｉｎｇｓｇｒｅａｔｓｏｒｒｏｗｔｏｔｈｅｐｅｏｐｌｅｉｎｔｈｉｓｒｅｇｉｏｎｂｅｃａｕｓｅｔｈｅｒａｐｉｄｓｉｌｔａｔｉｏｎｏｆｔｈｅｃｈａｎｎｅｌｂｒｉｎｇｓａｂｏｕｔｓｅｒｉｏｕｓｐｒｏｂｌｅｍｓｆｏｒｆ…     

A NON-UNIFORM SEDIMENT TRANSPORT MODEL WITH THE BOUNDARY-FITTING ORTHOGONAL COORDINATE SYSTEM

1. INTRODUCTIONSome problems have to be considered in the mathematical modeling for river engineering. The riverbed is always in the manner of deposition and erosion. The sediment transport is often in the state of non-equilibrium. General, the compositio…     

FLOW STRUCTURE AND SEDIMENT TRANSPORT WITH IMPACTS OF AQUATIC VEGETATION

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.     

FLOW FIELD CHARACTERISTICS OF THE SAND FUNNEL AND ITS MECHANICS OF SEDIMENT TRANSPORT

The flow in funnel chamber is typical three-di-mensional flow. The experimental results of clear water flowfield and muddy water flow field show that the flow character-istics in the funnel chamber are favorable to the separation ofwater and sand. Tangential velocity sustains the vortexstrength of the funnel chamber, axial velocity is benefit to thesediment sinking, and radial velocity is benefit to sedimentmoving to desilting hole. So the sand funnel is successful insediment disposal. The sand funnel projection has also gooddesilting effectiveness in practice. Its average flushing dis-charge is 3% of inlet canal discharge, the sand disposal rate is100% for the sand with grain diameter of more than 0. 5mm,and is more than 90% for the sand with grain diameter of lessthan 0. 5mm.     

SEDIMENT TRANSPORT MODEL OF A WATERSHED

ＳＥＤＩＭＥＮＴＴＲＡＮＳＰＯＲＴＭＯＤＥＬＯＦＡＷＡＴＥＲＳＨＥＤ１ＬＩＨｕａｉｅｎ２ＡＢＳＴＲＡＣＴＴｈｅｎａｔｕｒａｌｗａｔｅｒｓｈｅｄｉｓｓｉｍｐｌｙｒｅｐｒｅｓｅｎｔｅｄｂｙａｍｕｌｔｉｏｒｄｅｒｒｉｖｅｒｎｅｔｓｙｓｔｅｍ，ｓｏｔｈｅｓ...     

A VERTICAL 2-D NUMERICAL SIMULATION OF SUSPENDED SEDIMENT TRANSPORT

Numerical simulation of sediment transport and bed evolution has become an important technique in the sediment research. In this article,a numerical model of suspended sediment transport was proposed,which was established in the vertical σ coordinate for fitting the free surface and bottom. In the research of the sediment transport,the predominant factors were found to be the eddy diffusion,the settling velocity,the bed condition and so on. By the aid of the model in the article,the contribution of the Rouse parameter to the vertical profile of sediment concentration was clarified,which was identical to the theoretical results. In the comparison of the numerical results with laboratory data,the agreement between experimental data and numerical results was reached except for some data. And the possible reasons for the disagreement were discussed.     

A STUDY ON NONEQUILIBRIUM TRANSPORT OF NONUNIFORM BEDLOAD IN STEADY FLOW

In the case of steady flow, an equilibrium state for an alluvial reach referring tothe input of sediment over a sufficiently long time (time interval in the order of months) is equalto the output of sediment. A nonequilibrium state exists under steady flow when the sedimenttransport rate changes with time and space, so that there is no balance between input and outputof sediment. The experiments were performed in an open circuit tilting flume with the bed slope of 0.001-0. 009, the flume length of 30m and flume width of 0. 5m. The boundary condition atupstream and in all experiments, the rate of sedimant supply was zero. The coal or sand was se-lected as the Wed material. The grain diameter of the bed material varied in the range of 0.05-20. 00ram. The equation of nonequilibrium transport of nonuniform bedload is derived. Thegrain distribution of the size distribution of bedload is calculated by modified Gessler's formula.The grain size distribution of bed material is calculated by CARICHAR mixed layer model. These equations are applied to numerical simulation of armoring of riverbeds. The results ofthe bedload transport rate and the grain size distribution of the bedload at the end of the down-stream in the process of time, as well as the grain size distribution of the bed material in the pro-cess of time and distance are all in close agreement with the measurements.     

NUMERICAL MODELING OF SUSPENDED SEDIMENT TRANSPORT IN CHANNEL BENDS

1. INTRODUCTION Due to the fact that three-dimensional (3D) numerical models are quite expensive to simulate flow and sediment transport processes, vertically-integrated two-dimensional (2D) models are extensively applied at present, even to the predictio…     

NUMERICAL SIMULATION OF THE TIDAL MOTION AND SUSPEND EDSEDIMENT TRANSPORT IN THE RADIAL SANDBANK AREA OF THE SOUTHERN YELLOW SEA

A coupled 2-D numerical model for hydrodynamic-sediment transport was established and applied to simulate the tides, tidal currents and sediment movement in the submarine Radial Sandbank area of the southern Yellow Sea.With a high-resolution topography dataset used in the model,the simulation reproduced a fine-structured current field and erosion-siltation distribution. The modeled results show that,in the area of Radial Sandbanks, reversing tidal current and seabed erosion occurs within troughs while tidal current with more rotary feature and deposition occurs above sandbanks,which indicates the tidal-induced formation of the Radial Sandbanks. During a tidal period, associating with the variation of current speed, erosion alternates with siltation. The seabed deformation depends on the relative strength of erosion and siltation in a tidal period.     

基于实测资料的边坡稳定性评价突变模型

基于边坡失稳机理及特征，结合基于实测资料的统计模型，利用突变理论推导了边坡稳定的尖点突变模型和边坡稳定判据表达式．算例结果表明，该方法可行．     

柘林水库下游河道平面二维泥沙数学模型及其应用

对水库下游河床泥沙冲淤变化数值模拟研究已有很多报道，但对水库溢洪道下游具有天然覆盖层河道因未泄过洪水没有实测资料供模型验证，且覆盖层分层较明显和表层覆盖层具有粘性作用等，目前有关这方面研究成果报道较少。本文建立了正交曲线坐标系下平面二维泥沙数学模型，并应用于柘林水库下游河床泥沙冲淤变化计算，同时对计算中的有关参数选择进行了详细地分析，结果可供部门参考。     

SUSPENDED SEDIMENT TRANSPORT IN THE OFFSHORE NEAR YANGTZE ESTUARY

Based on the Estuarine, Coastal and Ocean Modeling System with Sediments （ECOMSED） model, a 3-D hydrodynamic-transport numerical model was established for the offshore area near the Yangtze Estuary in the East China Sea .The hydrodynamic module was driven by tide and wind. Sediment module included sediment resuspension, transport and deposition of cohesive and non-cohesive sediment. The settling of cohesive sediment in the water column was modeled as a fimction of aggregation （flocculation） and deposition. The numerical results were compared with observation data for August, 2006. It shows that the sediment concentration reduces gradually from the seashore to the offshore area. Numerical results of concentration time series in the observation stations show two peaks and two valleys, according with the observation data. It is mainly affected by tidal current. The suspended sediment concentration is related to the tidal current during a tidal cycle, and the maximum concentration appears 1 h-4 h after the current maximum velocity has reached.     

TRANSPORTATION CHARACTERISTIC OF BED LOAD FOR NON-UNIFORM SEDIMENT WITH EQUIVALENT GRAIN

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｃｏｎｄｉｔｉｏｎｏｆｉｎｃｉｐｉｅｎｔｍｏｔｉｏｎｏｆｓｅｄｉｍｅｎｔｉｓｏｎｅｏｆｔｈｅｍｏｓｔｂａｓｉｃｐｒｏｂｌｅｍｓｉｎｓｅｄｉｍｅｎｔｍｏｖｅｍｅｎｔｍｅｃｈａｎｉｃｓ .Ｔｈｉｓｐｒｏｂｌｅｍｈａｄｂｅｅｎｓ     

EXPERIMENTAL STUDY ON BED-LOAD SEDIMENT TRANSPORT IN IRREGULAR WAVE-CURRENT COEXISTENT FIELD

1.　INTRODUCTIONTheproblemofsedimenttransportnearcoastalregionisofgreatimportanceforthesiltationinnavigationalfairways,harbordocksandthechangesinbeachprofileandcoastalmorphology.Underpracticalconditions,dynamicenvironmentisverycomplexbecausethewaveandcurrentarerandomand,theirpropagatingdirectionsarealsouncertain.Sothestudyofsedimenttransportinanirregularwave-currentcoexistentfieldismoreimportantthanthatinpurewaveorpurecurrentfield.Inrecentyears,manyempiricalformulaswereproposedtoexpressth…     

CONCENTRATION DISTRIBUTION OF SEDIMENT IN BED LOAD LAYER

In this paper the concentration profile in bed load layer is derived based on kinetic theory. According to observations, particles moving in near wall region behave differently during ejection and sweeping of turbulence burst, as indicates that they are subject to different influences from turbulence, and therefore, the forces acting on particles are not the same. Consequently, particles moving in bed load layer are classified into two groups, one lifted upward by ejections, the other carried back to bed by sweepings, and the forces corresponding to upward and downward motions are proposed. By solving the basic transport equation of kinetic theory, the velocity distribution functions, upward and downward fluxes of particles in bed load layer are derived. Upon assumption of equilibrium sediment transport, concentration profile in bed load layer is obtained. Verification is also presented in this paper, which shows that the concentration profile produced by the relation proposed in this paper agrees with observations well.     

SIMULATION OF SOLUTE TRANSPORT USING A COUPLING MODEL BASED ON FINITE VOLUME METHOD IN FRACTURED ROCKS

The discrete version of solute transport equation for porous matrix depicted with the continuum model and the discrete fractured-network model are derived for fractured rocks with the Finite Volume Method(FVM).The two models are coupled according to the continuity condition of hydraulic head and concentration and the conservation of flow flux and mass flux in the contact plane between porous matrix and fractures.Numerical results show that the simulated concentration of the coupling model based on the FVM a...     

A SIMPLIFIED NUMERICAL MODEL OF 3-D GROUNDWATER AND SOLUTE TRANSPORT AT LARGE SCALE AREA

A simplified numerical model of groundwater and solute transport is developed. At large scale area there exists a big spatial scale difference between horizontal and vertical length scales. In the resultant model, the seepage region is particularly divided into several virtual layers along the z direction and vertical 1-D columns covering x-y 2-D area according to stratum properties. The numerical algorithm is replacing the full 3-D water and mass balance analysis as the 2-D Galerkin finite element method in x- and y-directions and 1-D finite differential approach in the z direction. The reasonable method of giving minimum thickness is successfully used to handle transient change of water table, drying cells and problem of rewetting. The solution of the simplified model is preconditioned conjugate gradient and ORTHOMIN method. The validity of the developed 3-D groundwater model is tested with the typical pumping and backwater scenarios. Results of water balance of the computed example reveal the model computation reliability. Based on a representative 3-D pollution case, the solute transport module is tested against computing results using the MT3DMS. The capability and high efficiency to predict non-stationary situations of free groundwater surface and solute plume in regional scale problem is quantitatively investigated. It is shown that the proposed model is computationally effective.