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Solving the estimation-identification problem in two-phase flow modeling
HYDROGEOLOGY:FLUID PRESSURE sorption on solute transport is mediated by the magnitude of transformation. (from Author)
961082 Calculation of interoodnl transmissivities in finite different models of flow in heterogeneous porous media R. K. Romeu & B. Noetinger, Water Resources Research, 31(4), 1995, pp 943-959. Presents an analytical and numerical investigation of the finite difference computation of the equivalent conductivity of heterogeneous porous media. The customary harmonic scheme to evaluate finite difference internodal transmissivities produces a systematic bias in the numerical results unless an extremely fine grid is used. In order to quantify such effects, an analytical approach, in the form of a series expansion of the equivalent numerical conductivity in powers of the conductivity variance was developed. The calculation confirms the existence of a strong bias and of a very slow convergence. A simple method to correct it, which is well suited for upscaling, is proposed. (from Authors) 961083 Finite difference methods for modeling porous media flows B. Das, S. Steinberg, S. Weber & S. Schaffer, Transport in Porous Media, 17(2), 1994, pp 171-200. The purpose of this study is to determine what finitedifference algorithms are best used in numerical simulation of two-dimensional single-phase saturated porous media flows when the models have a nondiagonal symmetric tensor for the mobility (or hydraulic conductivity) that has nontrivial jump discontinuities along fines that are not aligned with the coordinate axes. The answer is surprising, the simplest finite-difference method, called the MAC Scheme with Linear Averaging, performs nearly as well as most other algorithms over a wide range of problems. (from Authors)
961084 Improved computation of non-linear advection in porous media using slightly modified basic finite element algorithms P. Perroehet, International Journal for Numerical & Analytical Methods in Geomechanics, 19(7), 1995, pp 497-508. The numerical stability of standard finite element schemes applied to the advection/diffusion equation is evaluated using a space-time eigenvalue analysis. This analysis describes the spatial stability of the solutions, therefore the one-dimensional advection-diffusion equation is put into an alternative semi-discrete form which allows the derivation of a vary practical stability condition. In multidimensional flow situations the latter is applied along the streamlines by means of a tensorial corrective function that prevents excessive numerical smearing of fronts or phase interfaces. This is illustrated by an example which successfully simulates the coupling of two low miscible fluid phases in a variable saturated porous medium. (from Author) 961085 The local change of scale method for modelling flow in natural porous media (I): numerical tools Y. Anguy & D. Bernard, Advances in Water Resources, 17(6), 1994, pp 337-351. The local change of scale method couples the macroscopic permeability tensor K with the micro-geometry of the porous medium. This paper discusses the successful implementation of this procedure using both the impfieit finite element (IFE) and explicit finite volume (EFV) methods. In this implementation it is clear that the classical representative elementary volume (REV) is too small and must be repalced by the larger 'Darcy representative elementary volume'. The validity of the implementation is demonstrated by producing the correct results on a simple periodic array where analytic solution exists. Maps of local pseudo-velocity and pseudo-pressure fields in analogues of diageneticaUy perturbed media are realistic. For several cases of diagenetically perturbed media, the EFV method is sufficient. (Authors)
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961086 A model for the constant-head pumping test conducted in vertically fractured media J. M. Markle, R. K. Rowe & K. S. Novakowski, International Journal for Numerical & Analytical Methods in Geomechanics, 19(7), 1995, pp 457-473. The model is developed for a partially penetrating well that has a finite thickness skin, and intersects a single vertical fracture. The fracture is fully confined and flow occurs only in the fracture. The model is developed using Laplace transform and finite Fourier transform methods. Dimensionless curves are used to study the effects of a finite thickness skin and a partially penetrating wellbore. In the presence of a finite thickness skin, or a partially penetrating wellbore, a typical flow response for the constant-head pumping test has three distinct periods of flow corresponding to small-, intermediateand large-time. (from Authors) 961087 A comparison of fracture mixing models, 1. A transfer function approach to mass transport modeling J. A. Kupper, F. W. Schwartz & P. M. Steffler, Journal of Contaminant Hydrology, 18(1), 1995, pp 1-32. This paper develops a transfer function approach to mass transport modeling as a basis for comparing fiowline routing or complete mixing models in two-dimensional fracture networks. The approach accounts for physical and chemical processes in the network, and for diffusion, retardation and kinetic decay in the matrix blocks. In essence, the approach combines numerical and analytical approaches at the fracture scale to route mass through fracture segments and intersections. The accuracy of the approach is examined through tests comparing results with an analytic solution and a simple network problem. (from Authors) 961088 A comparison of fracture mixing models, 2. Analysis of simulation trials J. A. Kupper, F. W. Schwartz & P. M. Steffler, Journal of Contaminant Hydrology, 18(1), 1995, pp 33-58. This paper describes the application of a transfer function approach developed to model mass transport in a network of fractures subject to advection and dispersion within the fractures, and matrix diffusion. The model is able to treat mass mixing at fracture intersections by either flowline routing or complete mixing. This feature of the model is exploited in examining the question of whether the choice of a particular model significantly influences the pattern of mass transport in a fractured medium. The results showed that the case of uniform flow most emphasized the difference in the two mixing models, while in the case of strongly radial flow there was no difference in mass distributions measured through normalized breakthrough curves. (Authors) 961089 Solving the estimation-identification problem in two-phase flow modeling S. Finsterle & K. Pruess, Water Resources Research, 31(4), 1995, pp 913-924. A procedure is presented to solve the estimation-identification problem in two-phase flow modeling. Given discrete observations made on the system response, an optimum parameter set is derived for an appropriate conceptual model by solving the inverse problem using standard optimization techniques. Subsequently, a detailed error analysis is performed, and nonlinearity effects are considered. The iteractive process of model identification and parameter estimation for a ventilation test performed at the Grimsel Rock Laboratory, Switzerland is discussed. (from Authors) 961090 Application of boundary-fitted coordinate transformations to groundwater flow modeling Kang-Kun Lee & D. I. Leap, Transport in Porous Media, 17(2), 1994, pp 145-169.
961082 Calculation of interoodnl transmissivities in finite different models of flow in heterogeneous porous media R. K. Romeu & B. Noetinger, Water Resources Research, 31(4), 1995, pp 943-959. Presents an analytical and numerical investigation of the finite difference computation of the equivalent conductivity of heterogeneous porous media. The customary harmonic scheme to evaluate finite difference internodal transmissivities produces a systematic bias in the numerical results unless an extremely fine grid is used. In order to quantify such effects, an analytical approach, in the form of a series expansion of the equivalent numerical conductivity in powers of the conductivity variance was developed. The calculation confirms the existence of a strong bias and of a very slow convergence. A simple method to correct it, which is well suited for upscaling, is proposed. (from Authors) 961083 Finite difference methods for modeling porous media flows B. Das, S. Steinberg, S. Weber & S. Schaffer, Transport in Porous Media, 17(2), 1994, pp 171-200. The purpose of this study is to determine what finitedifference algorithms are best used in numerical simulation of two-dimensional single-phase saturated porous media flows when the models have a nondiagonal symmetric tensor for the mobility (or hydraulic conductivity) that has nontrivial jump discontinuities along fines that are not aligned with the coordinate axes. The answer is surprising, the simplest finite-difference method, called the MAC Scheme with Linear Averaging, performs nearly as well as most other algorithms over a wide range of problems. (from Authors)
961084 Improved computation of non-linear advection in porous media using slightly modified basic finite element algorithms P. Perroehet, International Journal for Numerical & Analytical Methods in Geomechanics, 19(7), 1995, pp 497-508. The numerical stability of standard finite element schemes applied to the advection/diffusion equation is evaluated using a space-time eigenvalue analysis. This analysis describes the spatial stability of the solutions, therefore the one-dimensional advection-diffusion equation is put into an alternative semi-discrete form which allows the derivation of a vary practical stability condition. In multidimensional flow situations the latter is applied along the streamlines by means of a tensorial corrective function that prevents excessive numerical smearing of fronts or phase interfaces. This is illustrated by an example which successfully simulates the coupling of two low miscible fluid phases in a variable saturated porous medium. (from Author) 961085 The local change of scale method for modelling flow in natural porous media (I): numerical tools Y. Anguy & D. Bernard, Advances in Water Resources, 17(6), 1994, pp 337-351. The local change of scale method couples the macroscopic permeability tensor K with the micro-geometry of the porous medium. This paper discusses the successful implementation of this procedure using both the impfieit finite element (IFE) and explicit finite volume (EFV) methods. In this implementation it is clear that the classical representative elementary volume (REV) is too small and must be repalced by the larger 'Darcy representative elementary volume'. The validity of the implementation is demonstrated by producing the correct results on a simple periodic array where analytic solution exists. Maps of local pseudo-velocity and pseudo-pressure fields in analogues of diageneticaUy perturbed media are realistic. For several cases of diagenetically perturbed media, the EFV method is sufficient. (Authors)
llA
961086 A model for the constant-head pumping test conducted in vertically fractured media J. M. Markle, R. K. Rowe & K. S. Novakowski, International Journal for Numerical & Analytical Methods in Geomechanics, 19(7), 1995, pp 457-473. The model is developed for a partially penetrating well that has a finite thickness skin, and intersects a single vertical fracture. The fracture is fully confined and flow occurs only in the fracture. The model is developed using Laplace transform and finite Fourier transform methods. Dimensionless curves are used to study the effects of a finite thickness skin and a partially penetrating wellbore. In the presence of a finite thickness skin, or a partially penetrating wellbore, a typical flow response for the constant-head pumping test has three distinct periods of flow corresponding to small-, intermediateand large-time. (from Authors) 961087 A comparison of fracture mixing models, 1. A transfer function approach to mass transport modeling J. A. Kupper, F. W. Schwartz & P. M. Steffler, Journal of Contaminant Hydrology, 18(1), 1995, pp 1-32. This paper develops a transfer function approach to mass transport modeling as a basis for comparing fiowline routing or complete mixing models in two-dimensional fracture networks. The approach accounts for physical and chemical processes in the network, and for diffusion, retardation and kinetic decay in the matrix blocks. In essence, the approach combines numerical and analytical approaches at the fracture scale to route mass through fracture segments and intersections. The accuracy of the approach is examined through tests comparing results with an analytic solution and a simple network problem. (from Authors) 961088 A comparison of fracture mixing models, 2. Analysis of simulation trials J. A. Kupper, F. W. Schwartz & P. M. Steffler, Journal of Contaminant Hydrology, 18(1), 1995, pp 33-58. This paper describes the application of a transfer function approach developed to model mass transport in a network of fractures subject to advection and dispersion within the fractures, and matrix diffusion. The model is able to treat mass mixing at fracture intersections by either flowline routing or complete mixing. This feature of the model is exploited in examining the question of whether the choice of a particular model significantly influences the pattern of mass transport in a fractured medium. The results showed that the case of uniform flow most emphasized the difference in the two mixing models, while in the case of strongly radial flow there was no difference in mass distributions measured through normalized breakthrough curves. (Authors) 961089 Solving the estimation-identification problem in two-phase flow modeling S. Finsterle & K. Pruess, Water Resources Research, 31(4), 1995, pp 913-924. A procedure is presented to solve the estimation-identification problem in two-phase flow modeling. Given discrete observations made on the system response, an optimum parameter set is derived for an appropriate conceptual model by solving the inverse problem using standard optimization techniques. Subsequently, a detailed error analysis is performed, and nonlinearity effects are considered. The iteractive process of model identification and parameter estimation for a ventilation test performed at the Grimsel Rock Laboratory, Switzerland is discussed. (from Authors) 961090 Application of boundary-fitted coordinate transformations to groundwater flow modeling Kang-Kun Lee & D. I. Leap, Transport in Porous Media, 17(2), 1994, pp 145-169.