HR: 1340h
AN: H33F-0535    [Abstracts]
TI: Simulations and Theory of Density-Dependent Dispersion in Weakly Heterogeneous Porous Media
AU: * Landman, A
EM: a.j.landman@citg.tudelft.nl
AF: Faculty of Civil Engineering and Geosciences, Delft University of Technology, Mijnbouwstraat 120, Delft, 2628 RX Netherlands
AU: Schotting, R J
EM: schotting@geo.uu.nl
AF: Environmental Hydrogeology Group, Department of Earth Sciences, Faculty of Geosciences, University of Utrecht, Budapestlaan 4 P.O. Box 80021, Utrecht, 3508 TA Netherlands
AB: The effect of density gradients on dispersive mixing of miscible fluids is studied. Density gradients not only affect dispersive transport for unstable flow, but also can significantly affect dispersion under stable conditions. For vertical displacements, laboratory experiments show a reduction of the longitudinal dispersivity under the influence of stabilizing density gradients. Linear Fick's law for the dispersive flux is inadequate to model these experiments. Therefore, alternative theories have been developed that incorporate the effect of density gradients. In this study, accurate numerical simulations of vertical displacements in weakly heterogeneous porous columns are performed. The numerical results confirm experimental observations. Furthermore, the computed concentration profiles are used to validate nonlinear dispersion theories applicable for high density gradients. A comparison is made with the stochastic theory of Welty and Gelhar, with homogenization theory, and with the nonlinear dispersion theory of Hassanizadeh and Leijnse. For small variances in $\log k$, the stochastic and homogenization theory lead to reasonably good predictions of the computed concentration profiles and variances, without any fitting. In the theory of Hassanizadeh and Leijnse a fitting parameter is involved. This nonlinear dispersion parameter is not a true medium parameter, as it is found to be dependent on the flow rate and on the travel distance.
DE: 3210 Modeling
DE: 3230 Numerical solutions
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1869 Stochastic processes
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting