HR: 1340h
AN: H23D-1623    [Abstracts]
TI: Characterization of Mixing and Spreading in a Bounded Stratified Random Medium
AU: Zavala, V
EM: vanessa.zavala@upc.edu
AF: Technical University of Catalonia, Campus Nord (UPC), Modulo D-2, c/ Jordi Girona 1-3, Barcelona, 08034, Spain
AU: * Dentz, M
EM: marco.dentz@upc.edu
AF: Technical University of Catalonia, Campus Nord (UPC), Modulo D-2, c/ Jordi Girona 1-3, Barcelona, 08034, Spain
AU: Carrera, J
EM: jcarrera@ija.csic.es
AF: Institute of Earth Sciences Jaume Almera, c/ Lluis Sole i Sabaris s/n, Barcelona, 08028, Spain
AB: Matheron and de Marsily (1980) studied transport in a perfectly stratified infinite medium as an idealized aquifer model, for which they observed anomalous increase of the apparent longitudinal dispersion coefficient with the square root of time. Here, we investigate solute mixing and spreading in a vertically bounded stratified random medium. Large scale spreading and mixing is controlled by the dispersion time scale which measures the time for complete vertical mixing by local dispersion. Unlike for the infinite stratified medium, at asymptotically long times disorder-induced mixing and spreading is uniquely quantified by a constant "Taylor dispersion" coefficient. Preasymptotic transport, in contrast, is highly non-Fickian, characterized by the superdiffusive increase of the apparent dispersion coefficient. We focus on preasymptotic times and the transition to the asymptotic regime. The mechanisms that lead to enhanced solute spreading and mixing are studied in terms of effective dispersion coefficients that are derived from local moments, i.e., moments of the transport Green function (distribution density of a solute evolving from a point injection). We investigate spreading and mixing in single realizations as well as in an ensemble sense within a stochastic modeling framework. In the latter approach, the transport coefficients are defined as ensemble averages over all possible aquifer realizations.
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: 2007 Fall Meeting