Stochastic aggregation model (SAM) for DNAPL--water displacement in porous media

摘要

Source zone characterization of DNAPL in the subsurface is a necessary part of managing environmental risks. Modeling DNAPL--water displacement processes at the pore-scale can lead to greater insight and understanding of lateral spreading, the extent of vertical migration, and the final fluid distributions of dense non--aqueous phase liquids. A two-dimensional stochastic aggregation model is developed to study DNAPL--water displacement in porous media. The model is a modified diffusion limited aggregation model, and uses essential properties governing front stability as model input : DNAPL--water viscosity differences, DNAPL--water density differences, intrinsic permeability of the porous media, flow rate, and the inclination angle of the porous media from the horizontal. Due to the simplicity of the algorithm, this modeling technique can produce realistic DNAPL--water configurations much faster than conventional continuum approaches and allows for a Monte Carlo approach to be utilized. The model is validated through comparison to laboratory experiments involving 1,2-Dichloroethane, carbon tetrachloride, tetrachloroethylene, and mobile pyrogard 53. These experiments were performed at varying flow rates and angles of inclination from the horizontal.