HR: 1340h
AN: H33F-0523    [Abstracts]
TI: Analytic Element Solutions for Preferential Flow Around and Through Elliptical Inhomogeneities in the Vadose Zone
AU: * Bakker, M
EM: mbakker@engr.uga.edu
AF: Biological and Agricultural Engineering, University of Georgia, Athens, GA 30605 United States
AU: Nieber, J L
EM: nieber@umn.edu
AF: Biosystems and Agricultural Engineering, University of Minnesota, St. Paul, MN 55455 United States
AB: We present new analytic element solutions for flow around and through elliptical inhomogeneities in the vadose zone. The solutions are analytic, and thus there is no grid; boundary conditions along the elliptical inhomogeneities are met up to machine accuracy, provided that enough terms are used in the series solution. The pressure head, velocity and saturation may be computed analytically at any point in the vadose zone. The approach can handle an arbitrary number of elliptical inhomogeneities, and is limited only by the available computer power. In this presentation we will consider elliptical inhomogeneities that consist of coarser material than the surrounding media; the ellipses are embedded in an otherwise uniform downward flux. The hydraulic conductivity is represented by an exponential function of the pressure head (the Gardner model). Different functions are specified for the inside and the outside of an inhomogeneity; both the saturated hydraulic conductivity and the water retention parameters may differ between the inside and outside. The coarser-soil inhomogeneities may divert flow or contract flow, depending on the magnitude of the downward flux. The resulting preferential flow paths, in case of diversion also called funnel-type flow, may result in large variations of the velocity, much larger than for the equivalent case when flow is saturated. A comparison with a numerical solution will be presented to assess the grid refinement that is needed near inhomogeneity boundaries in finite element solutions of the same problem. Several initial studies of contaminant spreading through multiple elliptical inhomogeneities will be presented, clearly demonstrating the longitudinal spreading caused by advection through fields of ellipses, and the dependency of the longitudinal spreading on the magnitude of the downward flux.
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting