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Modeling 3D ground-water flow by modified finite-element method
262A
HYDROGEOLOGY:WATER
minerals, laminations and layering, lithology contrast and shale content, stress history, diagenesis, cross-bedding, and temperature and pressure are principal factors responsible for electric and hydraulic anisotropies. (from Author) 956886 Modeling 3D ground-water flow by modif~edfinite-element method Fan Xin Yu & V. P. Singh, Journal of Irrigation & Drainage Engineering - ASCE, 120(5), 1994, pp 892-909. A number of theoretical improvements were made to the finite-element formulation for modeling threedimensional steady and unsteady ground-water flow. First, the Gale&in method was combined with the collocation method to handle the time-derivative term of the governing equation. Second, the resulting system of ordinary differential equations was solved by using finite integration. The improved formulation was coded in FORTRAN. Four example cases were used to verify the model. (from Authors) 956087 Scale and directional dependence of macrodlspersivities in colonnade networks R. Khaleel, Water Resources Research, 30(12), 1994, pp 3337-335s. Macrodispersion in discrete colonnade network models is investigated using a series of Monte Carlo type numerical experiments. The numerical simulations consider fluid flow and advective transport through a squam flow region of a two-dimensional network of hexagonal colonnades. Microdisper.sivities are calculated as a function of the scale and orientation of the square flow region within the larger, parent geometry. The computed asymptotic and preasymptotic macrodispersivities are compared with available stochastic solutions for 2D isotropic heterogeniety in the horizontal plane. For individual realizations, nonergodic behavior is clearly apparent in the near-source, evolving region of transport, and the numerical data are quite variable between realizations. The study provides important insight on applicability of stochastic continuum theories to discrete colonnade network models having 2~ much greater than 1. (from Author) 956088 Nonlocal properties of nonuniform averaged flows in heterogeneous media P. Indelman & B. Abramovich, Water Resources Research, 30(12), 1994, pp 3385-3393. The properties of nonuniform average potential flows in media of stationary random conductivity are studied. The mathematical model of average flow is derived as a system of governing equations to be satisfied by mean velocity and mean head. The averaged Damy’s law determines the effective conductivity as an integral operator of the convolution type, relating the mean velocity to the mean head gradient in a nonlocal way. It is shown that the effective conductivity cannot be defmed tmiquely for potential flows. Two new asymptotic models of the averaged Darcy’s law are developed to be applicable to large and small scales of heterogeneity. (from Authors) 956089 Experimental studies on the effects of pipeflow on throughflow partitioniag R. C. Sidle, H. Xitahara, T. Terajima &LY. Nakai, Journal of Hydrology, 165(1-4), 1995, pp 207-219. A bench-scale experiment was conducted with a uniform sand to evaluate the effect of pipetlow on the overall hydrologic regime. Piezometric levels were highest and pipeflow was lowest when the high-roughness portion of the pipe was
PRESSURE
located at the downslope end of the box. Measured values of pipeflow for different hydraulic gradients in each experiment were related to piexometric head above the pipe raised to the 0.32-0.42 power. Pipeflow was proportional to matrix flow in the soil above the pipe raised to the power of 0.4-0.6. (from Authors) 956898 Conductive beat flow and tbermaUy iadoced fluid flow rround a well bore in a poroelastic medimu Yarlong Wang & E. Papamichos, Water Resources Research, 30(12), 1994, pp 3375-3384. Rock skeleton deformation in poroelastic media can have a great effect on fluid flow, while in turn, a pore pressure change may affect the deformation. Thermal loading enhances such effects because the thermal expansion (contraction) of both the solid skeleton and the pore fluid may lead to additional deformation. In this paper transient analytical solutions for temperature and pore pressure changes near a circular borehole under instantaneous temperature and fluid pressure changes inside the borehole are presented. The solutions couple conductive heat transfer with Darcy fluid flow, and a borehole under a nonhydrostatic farfield stress state is simulated. Taking Westerly granite as an example, it is concluded that the maximum thetmally induced pore pressure inside the rock formation can be 38% higher than the isothermal pore pressure, with a borehole temperature and fluid pressure change ratio (AT/Ap) = l”C/MPa. It is emphasized that the thermally induced pore pressure change can be sign&ant inside a low-permeability porous medium, and a coupled solution must be obtained to address the mechanical, hydraulic, and thermal responses appropriately. (from Authors) 956091 Modeling of multicomponent reactive transport in grolmndwater 1. Model development and evaluation A. L. Walter, E. 0. Frind, D. W. Blowes, C. J. Ptacek & J. W. Molson, Water Resources Research, 30(11), 1994, pp 3137-3148. MINTRAN is a new model for simulating transport of multiple thermodynamically react@ chemical substances in groundwater systems. It consists of two main modules, a finite element transport module (PLUMEZD), and an equilibrium geochemistry module (MINTEQAZ). The advantages of the coupled model include access to the comprehensive geochemical database of MINTEQA2 and the ability to simulate hydrogeological systems with realistic aquifer properties and boundary conditions under complex geochemical conditions. The model is primarily targeted toward groundwater contamination due to acidic mine tailings effluents but is potentially also applicable to the full range of geochemical scenarios covered by MINTEQA2. (from Authors) 956992 X ray and visible light transmission for laboratory measurement of two-dimensional satoration fields in thinslab systems V. C. Tidwell & R. J. Glass, Water Resources Research, 30( 1l), 1994, pp 2873-2882. Hypothesis testing for flow in unsaturated porous media is limited by the ability to measure dependent variables in heterogeneous and/or transient systems. Recently, a number of tools for nonintrusive measurement of water saturation in the laboratory have been developed. Here two alternative techniques, X-ray absorption and light transmission, are developed and demonstrated for imaging transient saturation fields in thin-slab porous systems. The techniques yield full two-dimensional saturation tields with high spatial and temporal resolution. Evaluation of these techniques is accomplished by direct comparison of X-ray and light data
HYDROGEOLOGY:WATER
minerals, laminations and layering, lithology contrast and shale content, stress history, diagenesis, cross-bedding, and temperature and pressure are principal factors responsible for electric and hydraulic anisotropies. (from Author) 956886 Modeling 3D ground-water flow by modif~edfinite-element method Fan Xin Yu & V. P. Singh, Journal of Irrigation & Drainage Engineering - ASCE, 120(5), 1994, pp 892-909. A number of theoretical improvements were made to the finite-element formulation for modeling threedimensional steady and unsteady ground-water flow. First, the Gale&in method was combined with the collocation method to handle the time-derivative term of the governing equation. Second, the resulting system of ordinary differential equations was solved by using finite integration. The improved formulation was coded in FORTRAN. Four example cases were used to verify the model. (from Authors) 956087 Scale and directional dependence of macrodlspersivities in colonnade networks R. Khaleel, Water Resources Research, 30(12), 1994, pp 3337-335s. Macrodispersion in discrete colonnade network models is investigated using a series of Monte Carlo type numerical experiments. The numerical simulations consider fluid flow and advective transport through a squam flow region of a two-dimensional network of hexagonal colonnades. Microdisper.sivities are calculated as a function of the scale and orientation of the square flow region within the larger, parent geometry. The computed asymptotic and preasymptotic macrodispersivities are compared with available stochastic solutions for 2D isotropic heterogeniety in the horizontal plane. For individual realizations, nonergodic behavior is clearly apparent in the near-source, evolving region of transport, and the numerical data are quite variable between realizations. The study provides important insight on applicability of stochastic continuum theories to discrete colonnade network models having 2~ much greater than 1. (from Author) 956088 Nonlocal properties of nonuniform averaged flows in heterogeneous media P. Indelman & B. Abramovich, Water Resources Research, 30(12), 1994, pp 3385-3393. The properties of nonuniform average potential flows in media of stationary random conductivity are studied. The mathematical model of average flow is derived as a system of governing equations to be satisfied by mean velocity and mean head. The averaged Damy’s law determines the effective conductivity as an integral operator of the convolution type, relating the mean velocity to the mean head gradient in a nonlocal way. It is shown that the effective conductivity cannot be defmed tmiquely for potential flows. Two new asymptotic models of the averaged Darcy’s law are developed to be applicable to large and small scales of heterogeneity. (from Authors) 956089 Experimental studies on the effects of pipeflow on throughflow partitioniag R. C. Sidle, H. Xitahara, T. Terajima &LY. Nakai, Journal of Hydrology, 165(1-4), 1995, pp 207-219. A bench-scale experiment was conducted with a uniform sand to evaluate the effect of pipetlow on the overall hydrologic regime. Piezometric levels were highest and pipeflow was lowest when the high-roughness portion of the pipe was
PRESSURE
located at the downslope end of the box. Measured values of pipeflow for different hydraulic gradients in each experiment were related to piexometric head above the pipe raised to the 0.32-0.42 power. Pipeflow was proportional to matrix flow in the soil above the pipe raised to the power of 0.4-0.6. (from Authors) 956898 Conductive beat flow and tbermaUy iadoced fluid flow rround a well bore in a poroelastic medimu Yarlong Wang & E. Papamichos, Water Resources Research, 30(12), 1994, pp 3375-3384. Rock skeleton deformation in poroelastic media can have a great effect on fluid flow, while in turn, a pore pressure change may affect the deformation. Thermal loading enhances such effects because the thermal expansion (contraction) of both the solid skeleton and the pore fluid may lead to additional deformation. In this paper transient analytical solutions for temperature and pore pressure changes near a circular borehole under instantaneous temperature and fluid pressure changes inside the borehole are presented. The solutions couple conductive heat transfer with Darcy fluid flow, and a borehole under a nonhydrostatic farfield stress state is simulated. Taking Westerly granite as an example, it is concluded that the maximum thetmally induced pore pressure inside the rock formation can be 38% higher than the isothermal pore pressure, with a borehole temperature and fluid pressure change ratio (AT/Ap) = l”C/MPa. It is emphasized that the thermally induced pore pressure change can be sign&ant inside a low-permeability porous medium, and a coupled solution must be obtained to address the mechanical, hydraulic, and thermal responses appropriately. (from Authors) 956091 Modeling of multicomponent reactive transport in grolmndwater 1. Model development and evaluation A. L. Walter, E. 0. Frind, D. W. Blowes, C. J. Ptacek & J. W. Molson, Water Resources Research, 30(11), 1994, pp 3137-3148. MINTRAN is a new model for simulating transport of multiple thermodynamically react@ chemical substances in groundwater systems. It consists of two main modules, a finite element transport module (PLUMEZD), and an equilibrium geochemistry module (MINTEQAZ). The advantages of the coupled model include access to the comprehensive geochemical database of MINTEQA2 and the ability to simulate hydrogeological systems with realistic aquifer properties and boundary conditions under complex geochemical conditions. The model is primarily targeted toward groundwater contamination due to acidic mine tailings effluents but is potentially also applicable to the full range of geochemical scenarios covered by MINTEQA2. (from Authors) 956992 X ray and visible light transmission for laboratory measurement of two-dimensional satoration fields in thinslab systems V. C. Tidwell & R. J. Glass, Water Resources Research, 30( 1l), 1994, pp 2873-2882. Hypothesis testing for flow in unsaturated porous media is limited by the ability to measure dependent variables in heterogeneous and/or transient systems. Recently, a number of tools for nonintrusive measurement of water saturation in the laboratory have been developed. Here two alternative techniques, X-ray absorption and light transmission, are developed and demonstrated for imaging transient saturation fields in thin-slab porous systems. The techniques yield full two-dimensional saturation tields with high spatial and temporal resolution. Evaluation of these techniques is accomplished by direct comparison of X-ray and light data