HR: 0800h
AN: H51F-0424    [Abstracts]
TI: A Macroscale Description of Mass Transfer and Dispersion in Highly Heterogeneous Porous Media: Developments Using the Method of Volume Averaging
AU: * Chastanet, J H
EM: chastaju@engr.orst.edu
AF: Oregon State University, Environmental Engineering 202 Apperson Hall, Corvallis, OR 97330 United States
AU: Wood, B D
EM: brian.wood@oregonstate.edu
AF: Oregon State University, Environmental Engineering 202 Apperson Hall, Corvallis, OR 97330 United States
AB: This work focuses on the macroscale transport of a passive solute in a highly heterogeneous medium. We have considered bimodal medium, similar to that studied by Rao et al. (1980, Soil Sci. Soc. Am. J., 44:684-688) which consists of low conductivity inclusions in a high conductivity background medium. Solute transport in this kind of media often shows non-Fickian tailing behavior as a result of the disparity between the characteristic times for convection and inter-region mass transfer. In this work, we have extended the two region macroscopic transport model previously developed by Ahmadi et al. (1998, Adv. Water Res., 22:59-86) and Cherblanc et al. (2003, Water Resour. Res., 39, doi:10.1029/2002WR001559). Whereas these previously reported efforts focused on the asymptotic value of the macroscale effective mass exchange coefficient, α, we have focused on the case where α exhibits a non-negligible transient evolution. The macroscale mass transfer coefficient is determined from the solution to a transient closure problem defined for a representative region of the porous medium. By solving this closure problem via a finite element method, it is possible to calculate the mass exchange coefficient for the transient regime for relatively general conditions. The results of the work show significant variation of the mass exchange coefficient with the time under conditions where the ratio of the conductivities becomes large; for these conditions, the time-evolution of α may influence the macroscopic behavior. A comparison is made with results from the literature for some simplified cases (Rao et al., 1980).
DE: 1829 Groundwater hydrology
DE: 1839 Hydrologic scaling
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: Fall Meeting 2005