Compositional simulation of groundwater contamination by organic compounds: 1. Model development and verification

Abstract

A compositional simulator is developed for application to the analysis of contamination and remediation of groundwater systems. Simultaneous flow of three fluid phases (water, gas, and organic) is modeled. Interphase partitioning and transport of an arbitrary number of organic and inorganic components can be simulated. Phase densities are functions of pressure and phase composition. The model includes several numerical options, ranging from fully implicit with first-order upstream weighting to implicit in pressure, explicit in saturations and concentration with third-order upstream weighting. The model is verified to the extent possible with analytical solutions for simplified cases of multiphase flow and contaminant transport. The accuracy and efficiency of the various numerical options used in the model are illustrated.

Auxiliary analyses in support of performance assessment of a hypothetical low-level waste facility: Two-phase flow and contaminant transport in unsaturated soils with application to low-level radioactive waste disposal. Volume 2

“…The work of Sleep and Sykes (1989) also used the IMPES, solving the Richards equation for the water phase and then explicitly calculating the behavior of the air phase. In a more recent work, Sleep and Sykes (1993) compared the accuracy and efficiency of both an IMPES scheme and a fully implicit scheme. They found that the IMPES was more restricted in time step size than the fully implicit scheme.…”

“…The strong tradition of the use of this method dates back to early applications to petroleum reservoir problems. Among the numerous users of this method are: Pinder and Abriola (1986) who solved the fully coupled three phase problem using an implicit finite difference model with a Newton Raphson non-linear iteration scheme, with the assumption of a constant-pressure immobile gas phase, Pmess (1987) with the coupled heat and mass flow model TOUGH Sleep and Sykes (1989); Culver et al (1991); Moridis and Reddell (1991);and Sleep and Sykes (1993) whose model is one of the most complete currently available. The model of Sleep and Sykes (1993) solves the fully coupled air and water flow equations and includes contaminant transport in both phases.…”

“…Weeks et al (1982) were some of the first to use a numerical model to study transport in the unsaturated zone. The finite difference models range form the simple one-dimensional model of Rosenblwm (1993), through to the comprehensive model of Sleep and Sykes (1993). The finite difference models have used forward Euler (explicit) time stepping (Benson et al 1993), variably weighted Euler (Crank-Nicholson) time stepping (Baehr and Corapcioglu 1987) or backward Euler (fully implicit) time stepping [Sleep andSykes (1993), Rathfelder (1991)l.…”

“…The finite difference models range form the simple one-dimensional model of Rosenblwm (1993), through to the comprehensive model of Sleep and Sykes (1993). The finite difference models have used forward Euler (explicit) time stepping (Benson et al 1993), variably weighted Euler (Crank-Nicholson) time stepping (Baehr and Corapcioglu 1987) or backward Euler (fully implicit) time stepping [Sleep andSykes (1993), Rathfelder (1991)l. Sleep and Sykes (1993) present an excellent summary of the arguments for the different forms of temporal discretization.…”

Simulation des transferts réactifs multi-constituants au sein des lits d’infiltration percolation – évaluation des capacités d’oxygénation

“…Du fait de la complexité de la représentation du biofilm (modèles de Monod, des Micro-colonies et du Biofilm) et des interactions physico-chimiques, la majorité des problèmes traités sont unidimentionnels. Quelques modèles numériques bidimensionnels (RIFAI et al, 1988;ODENCRANTZ, 1992;MILLS et al, 1991) et tridimensionnels (SLEEP et SYKES, 1993;ZHENG, 1993) ont toutefois été développés. Optant pour une simplicité dans l'approche modélisatrice qui n'enlève rien à une exploitation efficiente des résultats, le problème étudié ici est unidimensionnel.…”