HR: 12:05h
AN: H42A-08    [Abstracts]
TI: Simulating Drainage and Imbibition Using Dual Models of Pore Spaces
AU: * Glantz, R
EM: roland_glantz@jhu.edu
AF: Johns Hopkins University, Department of Geography and Environmental Engineering, 313 Ames Hall, 3400 N. Charles Street, Baltimore, MD 21218 United States
AU: Hilpert, M
EM: markus_hilpert@jhu.edu
AF: Johns Hopkins University, Department of Geography and Environmental Engineering, 313 Ames Hall, 3400 N. Charles Street, Baltimore, MD 21218 United States
AB: When simulating drainage and imbibition using pore networks one usually relies on simplifying assumptions on the shape of the pore bodies and the pore channels. For instance, the pore bodies are assumed to be cubic and the pore channels are assumed to have triangular, rectangular, or circular cross sections. Our aim is to overcome these simplifying assumptions by incorporating more information on the shape of the pore space into the network. Given a 3D synthetic porous medium, e.g., a sphere packing, or a 3D image of a real porous medium the following three questions arise: (1) how to define and compute a pore network that is linked to explicit descriptions of the pore bodies and the channels in the actual pore space, (2) how to use this additional information when simulating drainage and imbibition, and (3) how to do the upscaling from the network scale to larger scales? To answer the first question we present a polyhedral model for pore spaces that we call the dual model. Once a polyhedral approximation of the pore space has been calculated, the dual model is unique and free of parameters. It consists of two parts related by duality: a decomposition of the pore space into contractible pore bodies and a pore network that is homotopy equivalent to the pore space. The pore bodies are unions of relatively open Delaunay cells with respect to the corners of the pore space, and the pore network consists of certain at most 2D Voronoi cells with respect to the corners of the pore space. By duality, any vertex of the network corresponds to a polyhedral pore body, and any network edge corresponds to a polyhedral pore channel. To answer the second question we (a) equip the polyhedral pore bodies and channels with shape parameters, (b) run Lattice-Boltzmann simulations of drainage (imbibition) in the individual pore channels (bodies), and (c) identify the shape parameters that most reliably predict the critical capillary pressure for the drainage (imbibition) of a pore channel (body). To answer the third question we will determine a critical macroscopic capillary pressure for drainage through bond percolation, where the bonds are the pore channels. Analogously, a critical macroscopic capillary pressure for imbibition is determined through site percolation, where the sites are the pore bodies.
DE: 0540 Image processing
DE: 1839 Hydrologic scaling
DE: 1847 Modeling
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005