HR: 1340h
AN: H23A-1421    [Abstracts]
TI: An Integrated Numerical and Experimental Study of DNAPL Dissolution and Mass Transfer in Porous Media.
AU: * Ezzedine, S M
EM: ezzedine1@llnl.gov
AF: Environmental Restoration Division, Lawrence Livermore National Laboratory, Mail Stop L-530 7000 East Aevenue, Livermore, CA 94551 United States
AU: Detwiler, R L
EM: detwiler1@llnl.gov
AF: Earth Science Division, Lawrence Livermore National Laboratory, Mail Stop L-201 7000 East Aevenue, Livermore, CA 94551 United States
AU: McNab, W W
EM: mcnab1@llnl.gov
AF: Environmental Restoration Division, Lawrence Livermore National Laboratory, Mail Stop L-530 7000 East Aevenue, Livermore, CA 94551 United States
AB: We seek to fundamentally enhance the understanding and modeling of DNAPL dissolution. Dissolution of DNAPL takes place at the microscopic level while remediation technologies are applied at the field scale. Building models that effectively represent the pore-scale processes requires developing techniques for quantifying these processes and their impact on large-scale mass transfer rates. We present an integrated experimental and computational approach aimed at quantitatively investigating the role of pore structure, entrapped DNAPL distribution and hydrodynamic conditions on core-scale mass transfer rates. This provides a systematic first step towards our ultimate goal of bridging, in a consistent way, the scale disparity.
At the microscale, a series of dissolution experiments have been conducted in glass cells. Pore space morphology and the evolving geometry of entrapped ganglia were measured using light transmission techniques. TCE was emplaced in the cell and by sequentially filling the pore space with dyed water under different flow rate allowed us to collect a large set of data of DNAPL dissolution. Such detailed measurements are critical to the understanding of the pore-scale interaction of hydrodynamics and mass transfer rates.
In parallel to the experiments, a numerical model was developed using adaptive mesh refinement (AMR) finite elements method (FEM). The numerical model solves simultaneously multiphase Navier-Stokes flow and transport with state-of-the art level-set interface tracking scheme. Adaptive mesh refinement allowed us to accurately truck the interface between the ganglion and water. Using published values of intrinsic physicochemical properties of TCE, this model was used to simulate experiments. Simulations indicated good agreement with the experiments. Once the evaluation of the numerical model is achieved, we numerically and experimentally evaluated the mass transfer rates of TCE for the different stages. Furthermore, by using a weighted average of the mass transfer rate at the interface with the fluid velocity at the interface allowed us to further eliminate the velocity effect and obtain a velocity-averaged mass transfer of TCE. Currently the model is being used for upscaling mass transfer rates to the mesoscale using synthetic porous media while experiments at the mesoscale are being conducted.
This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. UCRL-ABS-215074
DE: 1805 Computational hydrology
DE: 1832 Groundwater transport
DE: 1839 Hydrologic scaling
DE: 1847 Modeling
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
SC: Hydrology [H]
MN: Fall Meeting 2005