Transport of Immiscible Liquids

Eqnation 11.10 is valid for near-eqnilibrinm systems, so that it can be applied to mass-transfer limited processes, that is, systems in which the large scale rate of change of porosity is limited by the solnte flnx rather than the reaction kinetics. 

Application of this model showed that the complete reduction of porosity near the inlet does not lead to clogging of a system nonsupersaturated fluids are able to flow around closed regions and into more permeable areas where mixing and sub-seqnent deposition can occur. Thus, mixing-induced precipitation is expected to rednce porosity in concentrated regions rather than lead to evenly precipitated material throughout the porous domain. 

In partially saturated media, the moisture content affects NAPL migration significantly. Abriola and Pinder (1985) suggested that the flux of a phase p (NAPL, water, or air), J, can be written as 

Clearly, the actual pressure head in each phase depends on the fluid configuration within the pores. Hux equations for each of the three phases can be combined with mass conservation equations to derive governing transport equations. 

The relative permeability is difficult to quantify. It usually is estimated on the basis of laboratory experiments, as a function of relative saturation. In three-phase NAPL-water-air systems, each relative permeability is dependent on the relative saturation of each of the phases. Modeling based on empirical considerations can be employed. For example. Blunt (2000) discusses a model to estimate three-phase relative permeability, based on saturation-weighted interpolation of two-phase relative permeabilities. The model accounts for the trapping of the NAPL and air (gas) 

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