EXPERIMENTAL STUDIES OF SOLUTE TRANSPORT THROUGH AN UNSATURATED NATURAL SOIL

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A NEW NUMERICAL METHOD FOR GROUNDWATER FlOW AND SOLUTE TRANSPORT USING VELOCITY FIELD

A new numerical method for groundwater flow analysis was introduced to estimate simultaneously velocity vectors and water pressure head. The method could be employed to handle the vertical flow under variably saturated conditions and for horizontal flow as well. The method allows for better estimation of velocities at the element nodes which can be used as direct input to transport models. The advection-dispersion process was treated by the Eulerian-Lagrangian approach with particle tracking technique using the velocities at FEM nodes. The method was verified with the classical one dimensional model and applied to simulate contaminant transport process through a slurry wall as a barrier to prevent leachate pollution from a sanitary landfill.     

A NEW NUMERICAL METHOD FOR GROUNDWATER FIOW AND SOLUTE TRANSPORT USING VELOCITY FIELD

A new numerical method for groundwater flow analysis was introduced to estimate simultaneously velocity vectors and water pressure head. The method could be employed to handle the vertical flow under variably saturated conditions and for horizontal flow as well. The method allows for better estimation of velocities at the element nodes which can be used as direct input to transport models. The advection-dispersion process was treated by the Eulerian-Lagrangian approach with particle tracking technique using the velocities at FEM nodes. The method was verified with the classical one dimensional model and applied to simulate contaminant transport process through a slurry wall as a barrier to prevent leachate pollution from a sanitary landfill.     

STOCHASTIC ANALYSES OF ADSORBING SOLUTE TRANSPORT IN HETEROGENEOUS UNSATURATED SOILS

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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.     

SIMULATION OF SOLUTE TRANSPORT IN FRACTURED NETWORK WITH A PROBABILITY METHOD

The simulation of solute transport in fractured rock mass has been conducted with the Finite Difference Method(FDM), Finite Element Method(FEM) and Finite Analysis Method(FAM), etc.. However, groundwater flow and solute transport is very complex in fractured network compared to the rocks matrix because water flow and tracer particles have different selections of pathways when they travel to the fractured intersections. It is difficult for traditional method to simulate the law of solute transport in fractured network. Hence a new simulation method, the probability method, is developed. In the method, transfer probabilities for fractured network are calculated using the flux of input and output from fractured intersection points, and travel times of tracer particles are determined with random numbers, dispersion parameter and velocity. Furthermore, corresponding computing program is developed using the FORTRAN language. The comparison between simulated and experimental results shows that the probability method is of considerable reliability and is an effective method to simulate solute transport in fractured network, and the case study of the Jinping I-Hydropower Station displays its wide application prospect.     

QUALIFICATION OF UNCERTAINTY FOR SIMULATING SOLUTE TRANSPORT IN THE HETEROGENEOUS MEDIA WITH SPARSE GRID COLLOCATION METHOD

The sparse grid collocation method is discussed to qualify the uncertainty of solute transport. The Karhunen-Loeve (KL) expansion is employed to decompose the log transformed hydraulic conductivity. The head, velocity and concentration fields are represented by the Lagrange polynomial expansion. A sparse grid collocation method is then used to reduce the original stochastic partial differential equations to a set of deterministic equations which is collocated at selected interpolation (collocation) points. The collocation points are constructed by the Smolyak algorithm. The accuracy, efficiency and convergence property of sparse grid collocation method are investigated by numerical experiments. The analysis shows that stochastic collocation strategy helps to decouple stochastic computations, and all the numerical computation is possible to be implemented by existing deterministic finite element codes. The proposed method provides an efficient way to evaluate the uncertainty of the solute transport in the heterogeneous media.     

LABORATORY EXPERIMENTS ON SOLUTE TRANSPORT IN A PARTIAL TRANSFIXION SINGLE FRACTURE

In the study of solute transport in rough single fracture,the contact area is an important factor.The single fracture is defined as two categories in this article:the full transfixion single fracture and the partial transfixion single fracture.The purpose of this article is to research how the contact area affects the solute transport in partial transfixion single fracture.The contact area is generalized as square blocks with three sizes,and contact rate is variable,a series of experiments for solute transp...     

SOLUTE TRANSPORT IN NATURAL FRACTURES BASED ON DIGITAL IMAGE TECHNOLOGY

A method of fracture boundary extraction was developed using the Gaussian template and Canny boundary detection on the basis of the collected digital images of natural fractures. The roughness and apertures of the fractures were briefly discussed from the point of view of digital image analysis. The extracted fractured image was translated into a lattice image which can be directly used in numerical simulation. The lattice Boltzmann and modified moment propagation mixed method was then applied to the simulation of solute transport in a natural single fracture, and this mixed method could take the advantages of the lattice Boltzmann method in dealing with complex physical boundaries. The obtained concentrations was fitted with the CXTFIT2.1 code and compared with the results obtained with the commercial software Feflow. The comparison indicates that the simulation using the mixed method is sound.     

利用同一土柱测定土壤水分和保守性溶质运移参数

利用数学模型预测土壤水分和溶质运移过程的准确性取决于所涉及的水力参数和土壤溶质运移参数的可靠性和精度。目前由于实验系统和研究方法的限制,在测定水力参数和溶质运移参数时所采用的土壤样本不一致,产生了样本误差。本文建立了利用同一土壤样本测定水力参数和溶质运移参数方法,即首先进行水平一维入渗实验,待土壤饱和后改换为供溶液试验,测定土壤边界层随时间的变化过程从而计算出溶质运移参数。与传统的利用土壤溶质穿透曲线获得参数的方法比较表明,本文提出的方法是可行的。     

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...     

SIMULATION OF SOLUTE TRANSPORT IN A PARALLEL SINGLE FRACTURE WITH LBM/MMP MIXED METHOD

This article deals with the solute transport in a single fracture with the combination of the Lattice Boltzmann Method （LBM） and Modified Moment Propagation （MMP） method, and this mixed method is proved to have several advantages over the LBM and Moment Propagation （MP） mixed method which leads to negative concentrations under some conditions in computation. The disadvantage of LBM/MP has been overcome to a certain extent. Also, this work presents an LBM solution of modeling single fractures with uniformly or randomly distributed grains, which can provide a new path of applying the LBM in solute transport simulation in fractures.     

不流动水对包气带溶质运移的影响研究进展

本文对考虑不流动水影响下的溶质运移模型、可动-不动区溶质运移模型、考虑吸附与降解作用的不流动水溶质运移模型进行了综述。指出对不流动水的研究已从盲端水扩展到内聚体间不动的水和远离流动区的水。其中，用可动-不动区模型可解释溶质运移中穿透曲线不对称的现象；用压力圆盘渗透仪可直接测量不动区的含水量使上述模型易于操作。并指出今后不流动水研究的方向应为不流动水分类的完善、不流动水对包气带水流的影响研究、参数的不确定性和尺度效应研究。     

非饱和土壤中吸附性溶质运移的基本方程和参数结构

本文应用随机场的谱分析方法，研究了吸附性溶质在非饱和，非均匀土体中运动时平均浓度所遵循的基本方程。当非饱和水分运动以重务为主要作用力时，设经对数变换后的土壤饱和渗透系数，吸附系数和α参数为正态平稳随机场，求得了宏观弥散度的解析表达式。研究结果表明，宏观散度由三部分组成，分别来源于非饱和渗透系数的自相关函数，非饱和渗透系数吸附参数的互相关函数，以及吸附参数的自相关函数。     

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.     

非稳定流条件下非饱和均质土壤溶质运移的传递函数解

根据溶质运移的传递函数模型Tromsfer Function Model, TFM理论，研究了非稳定流条件下非饱和均质土壤中表施和原有NO-3 N及原有Cl-的运移。由极大似然法估算了模型参数μ和σ2，求出了溶质运移的概率密度函数，计算了NO-3 -N的淋失量，并利用土壤中原有Cl-的动态，对NO-3 N的迁移过程进行了模拟，同时还估算了溶质的中值迁移时间tm和均值迁移时间相应的运移体积θst和θst。     

地膜覆盖条件下土壤水及溶质运移规律的室内试验研究

针对黄淮海地区大面积种植棉花并采用地膜覆盖这一现状，采用室内模拟试验法，研究了地膜覆盖后土壤剖面上的水盐运移特点和规律．研究结果表明，在盐碱地上采用地膜覆盖，一方面可以减少土壤水分的蒸发，提高表层土壤的湿度；一方面由于通过土壤表层蒸发的水分减少，土壤中的盐分的表聚作用大为减弱，抑制了土壤返盐过程．     

A PREDICTING MODEL OF THE LIMITING FLUX FOR THE CHARGED SOLUTE IN ULTRAFILTRATION PROCESS

In the process of ultrafiltration , the occurrence of the limiting flux is elucidated with the formation of a cake(gel) layer on the membrane surface. Before cake formation, the pressure drop on the concentration polarization layer, as well as the permeate flux, increases with the applied pressure. The pressure drop on the concentration polarization layer, however, will no longer change with the applied pressure after the formation of the cake layer. The limiting flux will be obtained if the hydrodynamic conditions in the filtration channel are not affected by the cake layer. A mathematics model for predicting the limiting flux for the charged solute in ultrafiltration is developed. In this model, a repulsive electric force is taken into account in addition to convection and diffusion when the solute is carrying the same charge as the membrane material. A procedure to correlate the model with experimental ultrafiltration data is also present. The results show that a model in this paper is developed on a more realistic perception of the ultrafiltration system and the predicting data agrees well with experimental data.     

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

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

EXPERIMENTAL STUDY OF THE NON-DARCY FLOW AND SOLUTE TRANSPORT IN A CHANNELED SINGLE FRACTURE

The characterization of fracture rocks is always a key issue in understanding the flow and solute transport in fractured media. This article studies the solute transport in a Channeled Single Fracture (CSF), a single fracture with contact in certain areas. The flow in a CSF often has preferential pathways and the transport in a CSF often has Break Through Curves (BTCs) with long tails. The Surface Contact Ratio (SCR), the ratio of the contact area to the total fracture area, is an important indicator for th...