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Thin flow element and the problem of ill-conditioning
146A 903122 Experimental research on permeability of granular media Er-Hui, Z Ground Water ~ 7 . N6. Not'-Dec 1989. P848-854
Theoretical analysis suggests that permeability of granular media can be defined in terms of an external factor, hydraulic gradient, and internal factors, properties of the medium itself and of the fluid. It may be determined from a sieve analysis of the medium and characteristics of the fluid (density, viscosity). Experimental verification using sand and gravel soils is described.
903123 Expression for the permeability of anisotropic granular media Meegoda, N J: King. I P; Arulanandan, K int d Num Anal Meth Geomech VI3. N6, Nor-Dec 1989. P575-598
Soil permeability is a macroscopic parameter governed by events at a microscopic level. Assuming a spatially periodic porous soil medium, the Navier Stokes equation was solved by finite element analysis for several arrangements of the medium. Sensitivity analysis was used to derive an expression for permeability in terms of the basic variables which influence it: specific surface area, void ratio, particle shape, material heterogeneity, and arrangement of particles. Corresponding macroscopic variables are average specific surface area, average void ratio, anisotropy, tortuosity due to heterogeneity, and particle arrangement. Laboratory experiments are used to verify the proposed equations.
903124 Thin flow element and the problem of ill-conditioning Valliappan, S; Khalili-Naghadeh, N; Murti, V lnt J Num Anal Meth Geomech VI3. N6. Nol'-Dec 1989. P611-628
The problem of ill-conditioning in anisotropic and heterogeneous flow regions is studied. The conditioning ratio concept is introduced, which covers all factors possibly affecting ill-conditioning (aspect ratio, heterogeneity, anisotropy). It is demonstrated that above a limit value for this ratio, the stiffness matrix of the modelled region is ill-conditioned. A criterion to calculate the permeability normal to the fracture for thin elements is derived. Flow phenomena in a well intersecting a vertical fracture are modelled using thin elements with a very large aspect ratio. Results compare well with available analytical solutions.
903125 Transport of fluid and electric current through a single fracture Brown, S R J G¢ophys Res i/94. NB7. July 1989. P9429-9438
The analogy between fluid flow and electric current transport in rocks is extended to rough walled fractures, and differential equations derived for the conduction of fluids and electricity. These equations are used together with a fractal model of surface topography to numerically simulate flow in a single fracture. Different flow paths are seen for fluids and charged ions. Interpretation of results based on the parallel plate model leads to underestimation of hydraulic conductivity and total volume of fluid in the fracture. Transport properties of the single fracture are consistent with the single channel model.
903126 Diffusion and consumption of methane in an unsaturated zone in north-central Illinois. U.S.A. Striegl. R G: lshii, A L J Hydrol VII1, N1-4. Not, 1989. P133-143
Distribution of methane was measured in unsaturated till and eolian deposits adjacent to buried low level radioactive waste. Movement of the gas was simulated using a two dimensional finite difference model for gas diffusion in an unsaturated zone. Depth-concentration profiles indicated consumption of both atmospheric and waste generated methane in the unsaturated upper zone, presumably by micro-organisms. A term for consumption in the upper 2m was necessary to fit numerical model predictions to field measurements. 903127 Integral method solution for diffusion into a spherical block Zimmerman, R W: Bodvarsson, G S J Hydrol VII1, NI-4. Not' 1989, P213-224
An approximate analytical solution has been developed for the infiltration of a Newtonian fluid into a porous spherical block. Initial uniform fluid pressure in the block and constant pressure at the boundary are considered. Using the simple assumption of linear pressure profiles, instantaneous and cumulative fluxes can be predicted with suprising accuracy. The solution may be applied in double porosity models of fractured reservoirs and aquifers. 903128 Effects of coal seam permeability on the selection of a degasiflcation scheme Bise, C J; Sheetz, R S Min Engng V41. NIO. Oct 1989. P1035-1040
Determination of best degasification layouts for Iongwall mining over a seam permeability range of 5-60md has been studied. Both in situ horizontal boreholes and vertical stimulated boreholes are considered. Drilling layout, time and labour costs, and effect on mining were taken into account. At very low permeability, horizontal boreholes spaced at about 150m are suggested, and vertical boreholes in alternate panels when permeability is greater than 10md. 903129 Composite analytical model for analysis of pumping tests affected by well bore storage and finite skin thickness Novakowski, K S Water Resour Res V25. N9. Sept 1989, P193--1946
A composite analytical solution is presented for pumping tests with the influence of well bore storage and skin region of finite thickness taken into account. It is based on the Laplace transform method. The solution is verified by comparison with those considering well bore storage only, composite formation only, and well bore storage with infinitessimally thin skin. Effects of finite thickness skins of enhanced or reduced permeability, and of well bore storage on drawdown at early and late times are illustrated. 903130 Flow channeling in a single fracture as a two-dimensional strongly heterogeneous permeable medium. Technical note Tsang, Y W; Tsang. C F Water Resour Res k25. N9, Sept 1989. P2076-2080
Void space in a fracture is modelled as a 2 dimensional heterogeneous system with variable aperture, generated by geostatistical methods, in the fracture plane. Flow is across opposite faces of a rectangular fracture area. Certain preferred flow paths (channels) show the least resistance. Tracer transport is
C, 1990 Pergamon Press plc. Reproduction not permitted
Theoretical analysis suggests that permeability of granular media can be defined in terms of an external factor, hydraulic gradient, and internal factors, properties of the medium itself and of the fluid. It may be determined from a sieve analysis of the medium and characteristics of the fluid (density, viscosity). Experimental verification using sand and gravel soils is described.
903123 Expression for the permeability of anisotropic granular media Meegoda, N J: King. I P; Arulanandan, K int d Num Anal Meth Geomech VI3. N6, Nor-Dec 1989. P575-598
Soil permeability is a macroscopic parameter governed by events at a microscopic level. Assuming a spatially periodic porous soil medium, the Navier Stokes equation was solved by finite element analysis for several arrangements of the medium. Sensitivity analysis was used to derive an expression for permeability in terms of the basic variables which influence it: specific surface area, void ratio, particle shape, material heterogeneity, and arrangement of particles. Corresponding macroscopic variables are average specific surface area, average void ratio, anisotropy, tortuosity due to heterogeneity, and particle arrangement. Laboratory experiments are used to verify the proposed equations.
903124 Thin flow element and the problem of ill-conditioning Valliappan, S; Khalili-Naghadeh, N; Murti, V lnt J Num Anal Meth Geomech VI3. N6. Nol'-Dec 1989. P611-628
The problem of ill-conditioning in anisotropic and heterogeneous flow regions is studied. The conditioning ratio concept is introduced, which covers all factors possibly affecting ill-conditioning (aspect ratio, heterogeneity, anisotropy). It is demonstrated that above a limit value for this ratio, the stiffness matrix of the modelled region is ill-conditioned. A criterion to calculate the permeability normal to the fracture for thin elements is derived. Flow phenomena in a well intersecting a vertical fracture are modelled using thin elements with a very large aspect ratio. Results compare well with available analytical solutions.
903125 Transport of fluid and electric current through a single fracture Brown, S R J G¢ophys Res i/94. NB7. July 1989. P9429-9438
The analogy between fluid flow and electric current transport in rocks is extended to rough walled fractures, and differential equations derived for the conduction of fluids and electricity. These equations are used together with a fractal model of surface topography to numerically simulate flow in a single fracture. Different flow paths are seen for fluids and charged ions. Interpretation of results based on the parallel plate model leads to underestimation of hydraulic conductivity and total volume of fluid in the fracture. Transport properties of the single fracture are consistent with the single channel model.
903126 Diffusion and consumption of methane in an unsaturated zone in north-central Illinois. U.S.A. Striegl. R G: lshii, A L J Hydrol VII1, N1-4. Not, 1989. P133-143
Distribution of methane was measured in unsaturated till and eolian deposits adjacent to buried low level radioactive waste. Movement of the gas was simulated using a two dimensional finite difference model for gas diffusion in an unsaturated zone. Depth-concentration profiles indicated consumption of both atmospheric and waste generated methane in the unsaturated upper zone, presumably by micro-organisms. A term for consumption in the upper 2m was necessary to fit numerical model predictions to field measurements. 903127 Integral method solution for diffusion into a spherical block Zimmerman, R W: Bodvarsson, G S J Hydrol VII1, NI-4. Not' 1989, P213-224
An approximate analytical solution has been developed for the infiltration of a Newtonian fluid into a porous spherical block. Initial uniform fluid pressure in the block and constant pressure at the boundary are considered. Using the simple assumption of linear pressure profiles, instantaneous and cumulative fluxes can be predicted with suprising accuracy. The solution may be applied in double porosity models of fractured reservoirs and aquifers. 903128 Effects of coal seam permeability on the selection of a degasiflcation scheme Bise, C J; Sheetz, R S Min Engng V41. NIO. Oct 1989. P1035-1040
Determination of best degasification layouts for Iongwall mining over a seam permeability range of 5-60md has been studied. Both in situ horizontal boreholes and vertical stimulated boreholes are considered. Drilling layout, time and labour costs, and effect on mining were taken into account. At very low permeability, horizontal boreholes spaced at about 150m are suggested, and vertical boreholes in alternate panels when permeability is greater than 10md. 903129 Composite analytical model for analysis of pumping tests affected by well bore storage and finite skin thickness Novakowski, K S Water Resour Res V25. N9. Sept 1989, P193--1946
A composite analytical solution is presented for pumping tests with the influence of well bore storage and skin region of finite thickness taken into account. It is based on the Laplace transform method. The solution is verified by comparison with those considering well bore storage only, composite formation only, and well bore storage with infinitessimally thin skin. Effects of finite thickness skins of enhanced or reduced permeability, and of well bore storage on drawdown at early and late times are illustrated. 903130 Flow channeling in a single fracture as a two-dimensional strongly heterogeneous permeable medium. Technical note Tsang, Y W; Tsang. C F Water Resour Res k25. N9, Sept 1989. P2076-2080
Void space in a fracture is modelled as a 2 dimensional heterogeneous system with variable aperture, generated by geostatistical methods, in the fracture plane. Flow is across opposite faces of a rectangular fracture area. Certain preferred flow paths (channels) show the least resistance. Tracer transport is
C, 1990 Pergamon Press plc. Reproduction not permitted