Mass transfer and dispersion processes in connected conductivity structures : simulation, visualization, delineation and application

This thesis focuses on mass transfer behavior, i.e., tailing, in solute transport, and on hydraulic conductivity heterogeneity. Macrodispersive theory, generally used to incorporate heterogeneity into solute transport, does not account for this tailing and makes assumptions about the structural characteristics of the heterogeneity, specifically that the field is multivariate gaussian. We move away from the multigaussian assumption to focus on the concept of connected pathways of high or low conductivity. We first motivate the importance of connected extreme conductivity values through the numerical creation of two-dimensional conductivity fields with nearly identical univariate conductivity distributions and covariances, but with varying connectedness of extreme values. We simulated flow and transport through these fields, using a particle tracking approach that incorporates advection and diffusion. We demonstrate that connectedness impacts flow by influencing the effective conductivity of the field, and connected high conductivity fields with relatively high variance displayed mass transfer behavior, driven by both advective and diffusive processes. We then conducted laboratory experiments to study three flow situations demonstrated by the first part of the work - classic dispersion, diffusion-driven mass transfer, and advection-driven mass transfer. By simultaneously measuring outflow concentration and the spatial distribution of solute in the tank, we demonstrate different breakthrough characteristics driven by different small-scale processes. Outflow concentrations match excellently with established models in the case of diffusive mass transfer and dispersion, and relatively well with a model we developed for the advective mass transfer scenario.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Zinn, Brendan Anderson, 1977-

Advisor dc:contributor.advisor

• Charles F. Harvey.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29584

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29584