Modelling microscale flow and colloid transport in saturated porous media

Abstract

The microscale flow in soil porous media determines the transport of colloids contained in groundwater. In this paper, two completely different computational approaches, namely a mesoscopic lattice Boltzmann approach and a Navier–Stokes based hybrid approach, are applied to simulate pore-scale viscous flows. The porous medium is represented by a channel partially filled with circular (in 2D) or spherical (in 3D) particles. We demonstrate that the two approaches produce almost identical pore-scale flow field, providing a rigorous cross-validation for each approach. A Lagrangian particle-tracking approach is then used to study the transport of colloids in these flows. Due to the competing effects of hydrodynamic forces and electro-chemical interactions, it is shown that enhanced removal of colloids from the fluid by solid surfaces occurs when the residence time of colloids in a given flow passage is increased, in qualitative agreement with pore-scale visualisation experiments using confocal microscopy.

Keywords:

• porous medium
• saturated soil
• pore-scale flow
• direct numerical simulation
• lattice Boltzmann method
• colloid retention

Acknowledgements

This study is supported by the US Department of Agriculture (NRI, 2006-02551), US National Science Foundation (ATM-0527140) and National Natural Science Foundation of China (Project No. 10628206). The authors thank Ms. V.I. Lazouskaya for helpful discussions on the general topic of colloidal transport in both saturated and unsaturated soil.