ABSTRACT
Fluid density and viscosity of aqueous solutions are commonly assumed to be constants in most model simulations of water flow and solute transport in porous media. Circulation of fluids around salt domes, leaching of salts from soils during irrigation, flow of landfill leachate into groundwater aquifers, generation of salt water in lakes due to evaporation, are but a few important problems involving the flow of heterogeneous fluids in heterogeneous porous media. Accidental spillage of light nonaqueous phase liquids (LNAPL), such as gasoline, and dense nonaqueous phase liquids (DNAPL), such as polychlorinated biphenyls (PCB), over land areas also may introduce densityand viscosity-driven fluid flow in the vadose zone. Instability during liquid flow through porous media can be attributable to fluid heterogeneity as well as to heterogeneity within the media. The stability of the interface between two miscible fluids in a porous medium is a topic of active research in many disciplines.
