UVM Theses and Dissertations
Format:
Print
Author:
Oka, Ganesh K.
Dept./Program:
Mathematics
Year:
2014
Degree:
PhD
Abstract:
This research presents a model to upscale the effect of microscopic changes in pore geometry occurring due to bacterial biomass growth attached to soil particles, on the intrinsic permeability of the soil. A Cellular Automata based model (the CA model) is proposed in a dual role as an upscaling tool. Cellular Automata are used to model growth in biomass attached to soil particles and they also serve as Representative Elementary Volumes (REVs) for calculating the intrinsic permeability values. The states of cells in the CA model and rules for changing the states are presented.
The proposed CA model is coupled with a model for multiphase contaminant transport through porous media adapted for bacterial degradation of contaminants. This transport model is used as an upscaling environment for the CA model. The transport model is augmented with an equation for the growth in bacterial biomass attached to soil particles. This equation provides one link between the CA model and the transport model. The other link between these two models is the intrinsic permeability calculated by the CA model. The way these two models interact through these links is explained.
The coupling of the CA model and the transport model is used to simulate a column experiment demonstrating the reduction in permeability due to bacterial growth attached to sand particles. The two dimensional version of a computer code in the FORTRAN language implementing the transport model is used in simulations for computational ease. The transport model is suitably adapted for the two dimensional version by first expressing its equations in the cylindrical coordinate system and reducing the spacial dimensions from three to two using an averaging procedure. The details of this procedure are presented.
The mapping between the three dimensional grid of cells in the CA model and two dimensional finite element domain used for the solution of the transport model is explained. Multiple simulation runs are performed under different control conditions to analyze possible explanations for the observed reduction in intrinsic permeability in the column experiment. The simulations are also used for understanding the impact of some of the characteristics of the CA model on the calculated permeability values. The results of these simulations are presented.
The proposed CA model is coupled with a model for multiphase contaminant transport through porous media adapted for bacterial degradation of contaminants. This transport model is used as an upscaling environment for the CA model. The transport model is augmented with an equation for the growth in bacterial biomass attached to soil particles. This equation provides one link between the CA model and the transport model. The other link between these two models is the intrinsic permeability calculated by the CA model. The way these two models interact through these links is explained.
The coupling of the CA model and the transport model is used to simulate a column experiment demonstrating the reduction in permeability due to bacterial growth attached to sand particles. The two dimensional version of a computer code in the FORTRAN language implementing the transport model is used in simulations for computational ease. The transport model is suitably adapted for the two dimensional version by first expressing its equations in the cylindrical coordinate system and reducing the spacial dimensions from three to two using an averaging procedure. The details of this procedure are presented.
The mapping between the three dimensional grid of cells in the CA model and two dimensional finite element domain used for the solution of the transport model is explained. Multiple simulation runs are performed under different control conditions to analyze possible explanations for the observed reduction in intrinsic permeability in the column experiment. The simulations are also used for understanding the impact of some of the characteristics of the CA model on the calculated permeability values. The results of these simulations are presented.