HR: 0830h
AN: H11G-0932    [PDF]
TI: A Numerical Study of Hydrodynamic Dispersion in Porous Media: From Tracer to High Density
AU: * Landman, A
EM: a.j.landman@citg.tudelft.nl
AF: Section for Hydrology and Ecology, Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, Delft, 2600 GA Netherlands
AU: Schotting, R
AF: Section for Hydrology and Ecology, Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, Delft, 2600 GA Netherlands
AU: Johannsen, K
AF: Interdisciplinary Center for Scientific Computing, University of Heidelberg, Im Neuenheimer Feld 368, Heidelberg, D-69120 Germany
AB: The goal of this research is to investigate the non-linear effect of density gradients on hydrodynamic dispersion in porous media. We simulate stable upward displacements of fresh water by salt-water solutions in heterogeneous porous columns. The porous columns are heterogeneous with respect to the intrinsic permeability, which is log-normally distributed with an isotropic Gaussian correlation function. First, for the case of tracer dispersion three types of convergence were thoroughly investigated: numerical convergence, convergence of the ensemble averaging, and convergence of longitudinal dispersivity with respect to travel time. For single realizations, the observed dispersivities do not converge to the expected asymptotic value even after hundreds of correlation lengths. In the case of fluids differing in density, gravity forces stabilize the front, resulting in smaller effective dispersivities. Moreover, the uncertainty in the concentration values, averaged in the horizontal direction, reduces considerably compared to the tracer case. As a result, for high-density-gradient displacements fewer realizations are needed to obtain converged ensemble averaged results than in the tracer case.
DE: 1832 Groundwater transport
DE: 1869 Stochastic processes
DE: 3230 Numerical solutions
SC: Hydrology [H]
MN: 2003 Fall Meeting