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.     

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.     

STOCHASTIC ANALYSES OF ADSORBING SOLUTE TRANSPORT IN HETEROGENEOUS UNSATURATED SOILS

ＳＴＯＣＨＡＳＴＩＣ　ＡＮＡＬＹＳＥＳ　ＯＦ　ＡＤＳＯＲＢＩＮＧ　ＳＯＬＵＴＥ　ＴＲＡＮＳＰＯＲＴ　ＩＮ　ＨＥＴＥＲＯＧＥＮＥＯＵＳ　ＵＮＳＡＴＵＲＡＴＥＤ　ＳＯＩＬＳＳＴＯＣＨＡＳＴＩＣＡＮＡＬＹＳＥＳＯＦＡＤＳＯＲＢＩＮＧＳＯＬＵＴＥＴＲＡＮＳＰ...     

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.     

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.     

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 THROUGH THE VADOSE ZONE:FIELD STUDIES

ＳＯＬＵＴＥＴＲＡＮＳＰＯＲＴＴＨＲＯＵＧＨＴＨＥＶＡＤＯＳＥＺＯＮＥ：ＦＩＥＬＤＳＴＵＤＩＥＳ￥ＹｅＺｉ－ｔｏｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＨｙｄｒａｕｌｉｃＥｎｇ．，ＷｕｈａｎＵｎｉｖｅｒｓｉｔｙｏｆＨｙｄｒａｕｌｉｃａｎｄＥｌｅｃｔｒｉｃＥｎｇ...     

EXPERIMENTAL STUDIES OF SOLUTE TRANSPORT THROUGH AN UNSATURATED NATURAL SOIL

ＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＩＥＳＯＦＳＯＬＵＴＥＴＲＡＮＳＰＯＲＴＴＨＲＯＵＧＨＡＮＵＮＳＡＴＵＲＡＴＥＤＮＡＴＵＲＡＬＳＯＩＬ￥ＹｅＺｉ－ｔｏｎｇ；ＹａｎｇＪｉｎ－ｚｈｏｎｇ（ＷｕｈａｎＵｎｉｖｅｒｓｉｔｙｏｆＨｙｄｒａｕｌｉｃａｎｄＥｌｅｃ...     

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.     

WATER BREAKTHROUGH SIMULATION IN NATURALLY FRACTURED GAS RESERVOIRS WITH WATER DRIVE

NOMENCLATURE Δt———ti me increment T———fracture trans missibility Vb———bulk volume S———saturation K———formation permeabilityKr———relative permeability q———production rate Ф———fluid potential φ———porosity u———viscosity P———capillary pressure I———the exchange term L———fracture spacing ω———upstream weighting factor δ———shape factor ξ———inertial factor SUBSCRIPTS mac———macrofracture mic———microfracture m———matrix x———x-dire…     

A NEW APPROACH TO THE NUMERICAL SIMULATION OF MASS TRANSPORT

A refined numerical method, based upon time-line interpolation, for the simulation of advection and diffusion has been tentatively explored. A complete set of temporal reachback numerical scheme in applying the method of characteristics has been derived, and the favorable accuracy of the method demonstrated. The use of interpolations in time, rather than the more widely used interpolations in space, demonstrates that it generates a much smaller numerical error.     

SIMULATION OF THERMAL TRANSPORT IN AQUIFER： A GWHP SYSTEM IN CHENGDU, CHINA

With an established convection-dispersion model for the thermal transport in aquifer, the thermal transport processes in an unconfined aquifer of a Groundwater Heat Pump (GWHP) system in Chengdu, China, are simulated with double-well intervals and cooling-load design fluctuations in summer running period under special groundwater flow and heat source conditions, and the stage-characteristics of the thermal transport in the aquifer are investigated in the running cycle (1 year) numerically. The results show that the thermal transport in the aquifer is closely related to the distance between pumping and injecting wells and the cooling-load design fluctuations, especially, to the cycling water volume. The thermal transport in the aquifer sees different characteristics in the two states in the pumping-recharging stages in summer/winter and the storing stages in spring/autumn. With the hydro-geologic theory and the numerical model, the effect of the groundwater-flow on the thermal transport in the unconfined aquifer is discussed.     

NUMERICAL SIMULATION FOR CONTAMINANTS AND WATER TRANSPORT IN SOILS

ＮＵＭＥＲＩＣＡＬ　ＳＩＭＵＬＡＴＩＯＮ　ＦＯＲ　ＣＯＮＴＡＭＩＮＡＮＴＳ　ＡＮＤ　ＷＡＴＥＲ　ＴＲＡＮＳＰＯＲＴ　ＩＮ　ＳＯＩＬＳＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＦＯＲＣＯＮＴＡＭＩＮＡＮＴＳＡＮＤＷＡＴＥＲＴＲＡＮＳＰＯＲＴＩＮＳＯＩＬＳ￥Ｗａ...     

A CONSERVATION EQUATION OF CONCENTRATION VARIANCE FOR SOLUTE TRANSPORT IN HETEROGENEOUS FORMATIONS

To characterize the mean and variance of stochastic concentration distributions in heterogeneous porous media, we derived conservation equations using the first-order perturbation approach and assuming stationary fluctuation fields of velocity and concentration. The concentration variance equation, similar to the mean concentration equation, consists of convection and dispersion terms with the mean water velocity and macrodispersivity. In addition, there is a production term in the concentration variance e-quation. The concentration variance production is quadratically proportional to the mean concentration gradient with a coefficient Qij , defined as the concentration variance productivity , which is the difference between the macrodispersivity Aij and the local dispersivity aij multiplied by a four-rank tensor. The macrodispersivity and the local dispersivity, respectively, result in the creation and dissipation of the concentration variance. The concentration variance is produced if the concentration     

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.     

SIMULATION OF SEDIMENT DEPOSITION IN A CAVITY WITH FREE SURFACE

Studies of the flow and sediment movement in a cavity with free surface were mostly limited to physical modeling experiments. In this study, the sediment movement is characterized in detail using a 3-D turbulent numerical model. To close the Reynolds equations, the standard k-ε model is employed. The VOF method is adopted to capture the time varying free surface and the porosity method is introduced to deal with the irregular boundary and the varying bed deformation. The computation results agree well with the experimental data in major aspects such as the vertical distribution of the sediment concentration and the deposition topography in the cavity. The comparisons show that this model can well predict the flow structure and the sediment movement and also the river bed deformation in a cavity.     

DETERMINATION OF HEAT AND MOISTURE TRANSPORT PROPERTIES IN WET POROUS MEDIA USING THEPARAMETER ESTIMATION METHOD

1.INTRODUCTIONtheheatandmoisturetransportpropertiesinwetporousmediaareessentialdatatodealwithmanyengineeringproblemsandarealsooneofthemostimportantresearchobjectivesinthefieldofheatandmasstransferinwetporousmedia.Althoughmanymethodshavebeendevelopedtoanalyzetheheatandmoisturetransportpropertiesinwetporousmedia,theexistingdataoftheheatandmoisturetransportpropertiesaresodeficientthatthedatacannotmeettheneedsfortheoreticalresearchandengineeringapplicationsbecauseofthecomplexityintheheatandmas…     

NUMERICAL SIMULATION OF TRANSIENT CUTTINGS TRANSPORT WITH FOAM FLUID IN HORIZONTAL WELLBORE

With considering the interlayer mass transfer and fluid influx from the reservoir, a one-dimensional two-layer hydraulic model was established to describe the mechanism of transient cuttings transport with foam fluid in horizontal well section. The model was numerically calculated based on the modified SIMPLE algorithm, and the height of cuttings bed was predicted by the trial-and-error method. Sensitivity analysis was conducted on the affecting factors on the cuttings transport performance. Results show that cuttings deposition moves along the horizontal wellbore from the drilling bit, and finally achieves a steady state with dynamic balance. Dimensionless cuttings bed height decreases with the increase of foam quality or foam flow rate, but increases with the increase of drillpipe eccentricity, cuttings size or drilling rate. The influx of water and gas from the reservoir is helpful to improve the cuttings transport efficiency with foam. The proposed model offers theoretical guidelines for hydraulic parameter design and hole cleaning control in foamed horizontal drilling.