HR: 0800h
AN: H21D-1044    [Abstracts]
TI: New Insight into Discrete Particle Behavior in Porous Media
AU: Yoon, J S
EM: jyoon1@mit.edu
AF: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 United States
AU: * Culligan, P J
EM: pjc2104@columbia.edu
AF: Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027 United States
AU: Germaine, J T
EM: jgermain@mit.edu
AF: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 United States
AB: A new technique for visualizing discrete particle transport in the interior of a porous medium has been developed. The technique, which includes the construction of a translucent medium and the use of laser induced fluorescence for particle tracking, was used to examine the behavior of a 50 mg/L suspension of negatively charged, micron-size, non-Brownian particles in the interior of a porous medium that was 16.5 cm high x 10 cm wide x 2.4 cm thick. The porous medium was constructed from mono-size 4mm diameter glass beads saturated with distilled/ deionized water. Particle behavior as a function of pore fluid velocity and solid surface roughness was imaged at both the macroscopic and microscopic level. Experimental results reveal two interactions between the discrete particles and the solid phase of the medium. One, particle entrapment, resulted in the firm - but not necessarily irreversible - collection of particles at solid-solid contact points and asperities on the solid surfaces. The other, particle hindrance, resulted in non-firm interactions between the particles and the solid's contact points and surfaces. Particle entrapment in smooth bead systems occurred only at contact points, while in rough bead systems both contact and surface entrapment were observed. At low fluid velocities in the rough beads surface entrapment was dominant, while at high fluid velocities contact entrapment dominated. Changes in the concentration of particles that were entrapment or hindered were observed with distance from the particle injection point. These changes, which became more significant as the fluid velocity decreased, were attributed to particle size distribution effects. The results of this work demonstrate that the commonly used filtration theory can be inadequate for modeling the subsurface behavior of discrete particles, such as colloids.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting