Theory and implementation for SWIFT II. The Sandia waste-isolation flow and transport model for fractured media. Release 4. 84

This report is one of two that describe the three-dimensional finite-difference code SWIFT II. This code is used to simulate flow and transport processes in geologic media that may be fractured and was developed for use in the analysis of deep geologic nuclear waste-disposal facilities. However, it may be used in other areas such as waste injection into saline aquifers and heat storage in aquifers. Both dual-porosity and discrete-fracture conceptualizations may be considered for the fractured zones. In order to maximize computer efficiency, only one-dimensional migration is permitted within the rock matrix. Otherwise, the treatment of the matrix is general and entirely consistent with the treatment of the fracture and single-porosity zones. A variable density is included throughout, and a variety of options are available to facilitate the various uses of the code. This document presents the theory and formulation of the SWIFT II code. It is intended to be a comprehensive statement of the mathematical, numerical, and computer implementation of the code. A companion document, Data Input Guide for SWIFT II (NUREG/CR-3162), gives the input data guide.