A pore-scale study of transport of inertial particles by water in porous media

We study the transport of inertial particles in water flow in porous media. Our interest lies in understanding the accumulation of particles including the possibility of clogging. We propose that accumulation can be a result of hydrodynamic effects: the tortuous paths of the porous medium generate regions of dominating strain, which favour the accumulation of particles. Numerical simulations show that essentially two accumulation regimes are identified: for low and for high flow velocities. When particles accumulate at the entrance of a pore throat (high-velocity region), a clog is formed. This significantly modifies the flow, as the partial blockage of the pore causes a local redistribution of pressure, which diverts the upstream water flow into neighbouring pores. Moreover, we show that accumulation in high velocity regions occurs in heterogeneous media, but not in homogeneous media, where we refer to homogeneity with respect to the distribution of the pore throat diameters

Changes in the interfacial tension of chlorinated solvents following flow through UK soils and shallow aquifer material

The interfacial tension (IFT) that arises at the interface between water and an immiscible organic liquid is a key parameter affecting the transport and subsequent fate of the organic liquid in water-saturated porous media. In this paper, data are presented that show how contact between a range of soil types and chlorinated hydrocarbon solvent (CHS) dense nonaqueous phase liquids (DNAPLs) can affect DNAPL/water IFT values. The soils examined are indicative of U.K. soil types and shallow aquifer materials. The solvents investigated were tetrachloroethylene (PCE) and trichloroethylene (TCE). Lab grade, recovered field DNAPL and industrial waste chlorinated solvent mixtures were used. The data from batch and column experiments invariably revealed that water/DNAPL IFT values change following contact with unsaturated soils. In the majority of cases, the IFT values increase following soil exposure. However, after contact with an organic-rich soil, the I FT of the lab grade solvents decreased. The experimental evidence suggests that these reductions are linked to the removal of organic material from the soil and its subsequent incorporation into the solvent. IFT increases in the case of lab solvents are shown to be linked to the removal of stabilizers (added by the manufacturers to obviate degradation) that are removed by adsorption to soil mineral surfaces. Similarly, it is conjectured that adsorption of surface-active compounds from the industrial waste samples to soil surfaces is responsible for increases in the IFT in these samples. Finally, it was observed that invading CHSs are capable of dissolving and subsequently mobilizing in-situ soil contaminants. GC/MS analysis revealed these mobilized soil contaminants to be polyaromatic hydrocarbons and phthalate esters