HR: 09:50h
AN: H21H-08    [Abstracts]
TI: Formulation and Validation of and Interfacial Area Model for the Explicit Description of Rate Limited Mass Transfer in Multiphase Systems
AU: * Grant, G P
EM: g.p.grant@sms.ed.ac.uk
AF: Institute for Infrastructure and Environment The University of Edinburgh, Alexander Graham Bell Building The King's Buildings, Edinburgh, EH9 3JL United Kingdom
AU: Gerhard, J I
EM: j.gerhard@ed.ac.uk
AF: Institute for Infrastructure and Environment The University of Edinburgh, Alexander Graham Bell Building The King's Buildings, Edinburgh, EH9 3JL United Kingdom
AB: A significant amount of theoretical and laboratory research has been conducted to study the process of Dense Non-Aqueous Phase Liquid (DNAPL) dissolution. However, the difficulties associated with accurately estimating DNAPL / aqueous phase interfacial area has generally limited these studies to the derivation of empirical correlation models that are only valid under narrow conditions. This study focuses on: 1) the derivation of a rate-limited mass transfer model that includes an explicit description of DNAPL / aqueous phase interfacial area; and, 2) validation of this model such that, when incorporated into a numerical simulator, it is appropriate for predicting dissolution from a transient DNAPL release in heterogeneous porous media. The proposed thermodynamically-based interfacial area (IFA) model was validated with the results of a two-dimensional bench scale experiment involving the fixed volume release of 1,2-dichloroethane (1,2-DCE) into initially water-saturated, heterogeneous porous media. The DNAPL body, consisting of a complex distribution of pools and residual zones, was completely dissolved under a constant gradient while aqueous phase 1,2-DCE concentrations were measured over time at discrete downgradient locations. Simulations with the multiphase flow and aqueous phase transport model DNAPL3D-MT, incorporating the IFA model, successfully reproduced the observed dissolution behaviour. Furthermore, when the simulator alternatively employs a local equilibrium assumption (LEA) or an existing empirical correlation model, predicted dissolution behaviour was found to be much less accurate. Additional simulations, examining sensitivity to IFA model assumptions, reveal: 1) the importance of utilising an effective (as opposed to total) specific interfacial area estimate; and, 2) the insensitivity of overall dissolution rates to the interfacial area assigned to DNAPL residual blobs. Field scale simulations further illustrate the differences attained when employing different mass transfer models at a practical scale.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1847 Modeling
SC: Hydrology [H]
MN: Fall Meeting 2005