Doctor of Philosophy (PhD)
This dissertation presents a new numerical model of reactive polymer flow in heterogeneous porous media. A moment representation of the log-normal polymer molecular weight distribution is used to model polymer as a multi-component species. Three leading moments are used to simulate the polymer transport and reaction processes in a two-dimensional porous medium. A new operator splitting technique that allows the moment equations for polymerization to be incorporated into a finite-difference transport model is developed. The novelty of this approach is the use of two different dependent variables (for the transport versus reaction parts of the problem). It is significant from a physical standpoint because previous techniques did not allow us to observe the full evolution of polymer molecular weights in space and time. In this dissertation, two types of flows are examined. The first is the injection of a polymerizing fluid into a heterogeneous material containing low viscosity fluid (e.g., air or water). Simulations show that, depending on the Damkohler number, preferential loss of material permeability can occur in either low or high permeability regions. Because this effect dictates subsequent flow patterns, this result suggests that front stability can be controlled through proper design of the flow dynamics versus reaction dynamics. The formation of steady viscous fingers was observed, which is a fundamentally different phenomenon than previously observed transient viscous fingering formed during displacements. It is affected by the competition between reaction and convection, which allows the behavior to be correlated with the Damkohler number. A critical Damkohler number exists, above which steady-state conditions are not observed. The critical Damkohler number is affected by the Peclet number and permeability field. The second type of simulation is the injection of polymerizing fluids under conditions that lead to viscous instabilities. Results show the Damkohler number again to be a critical parameter. In both cases, the scale and structure of the material heterogeneities have a significant effect on the resulting flow. These research results provide important information for various polymer processing applications.
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Liu, Honggao, "Numerical studies of reactive polymer flows in porous materials" (2002). LSU Doctoral Dissertations. 1065.
Karsten E. Thompson