35 research outputs found
Evaluation of Vertical Leakage Schemes for Multilayer Sharp-Interface Saltwater-Intrusion Model
Ten Years of Research in Groundwater Transport Studies at Columbus Air Force Base, Mississippi
Soluções analĂticas de transporte de traçadores em rochas fracturadas, associadas a reacções de precipitação-dissolução
Precipitation-dissolution reactions are important for a number of applications such as isotopic tracer transport in the subsurface. Analytical solutions have been developed for tracer transport in both single-fracture and multiple-fracture systems associated with these reactions under transient and steady-state transport conditions. These solutions also take into account advective transport in fractures and molecular diffusion in the rock matrix. For studying distributions of disturbed tracer concentration (the difference between actual concentration and its equilibrium value), effects of precipitation-dissolution reactions are mathematically equivalent to a 'decay' process with a decay constant proportional to the corresponding bulk reaction rate. This important feature significantly simplifies the derivation procedure by taking advantage of the existence of analytical solutions for tracer transport associated with radioactive decay in fractured rock. It is also useful for interpreting tracer breakthrough curves, because the impact of a decay process is relatively easy to analyze. Several illustrative examples are presented, which show that the results are sensitive to fracture spacing, matrix diffusion coefficient (fracture surface area), and bulk reaction rate (or 'decay' constant), indicating that the relevant flow and transport parameters may be estimated by analyzing tracer signals
A Perspective on Time-Continuous Space-Discretized Solutions of Convection-Dispersion Equation in Variably Saturated Porous Media
Numerical modeling of colloid-facilitated radionuclide decay chain transport in a coupled fracture–matrix system
Migration of radionuclides from a high-level radioactive waste repository in deep geological formations
Visualized experimental investigation on the hydraulic characteristics of two-phase flow in a single smooth and single rough rock fractures
Influence of temporal fluctuations and spatial heterogeneity on pollution transport in porous media
The combined influence of temporal fluctuations and spatial heterogeneity on non-reactive solute transport mechanisms in porous media can be understood by performing simulations of steady and unsteady flow and transport in heterogeneous media. The study focuses on issues such as the degree of heterogeneity, correlation length, separation of the combined effects of temporal and spatial variations, and ergodicity conditions under unsteady flow conditions. It is shown that the effect of temporal variations on solute transport is masked by the strong effect of spatial heterogeneity. There is no obvious difference in plume shape between steady and unsteady flow conditions; the first and the second spatial moments of the plume of the unsteadystate flow condition fluctuate around the steady-state flow condition with the same period of oscillations as the input signal at small storage coefficient (S?0.001). At a relatively high standard deviation in hydraulic conductivity and a small storage coefficient, the unsteady flow condition sharpens the temporal variations in macrodispersion coefficients. The magnitude of the longitudinal macrodispersion coefficient under unsteady flow condition is almost doubled at the maximum values. However, the transverse macrodispersion coefficient fluctuates around zero. The Kubo number and Peclet number ranges are 1.2–64 and 10–250, respectively.Geoscience & EngineeringCivil Engineering and Geoscience