First Advisor

Albert S. Benight

Term of Graduation

Winter 2021

Date of Publication

3-9-2021

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Chemistry

Department

Chemistry

Language

English

Subjects

Chlorites, Autocatalysis, Fluid dynamics, Physical and theoretical chemistry

DOI

10.15760/etd.7540

Physical Description

1 online resource (xvi, 59 pages)

Abstract

Chemo-hydrodynamics generated from reaction-diffusion-convection processes of autocatalytic chemical systems are extensively studied for their applications in modeling complex systems. Compared to the more extensively studied autocatalytic systems, chlorite-tetrathionate and chlorite-trithionate, the chlorite-thiourea systems is relatively unexplored. Compared to the two previous systems, chlorite-thiourea has more straightforward chemical kinetics. To narrow the gap between chlorite-thiourea and the other systems a combination of experimental study and numerical simulation were employed to quantify this system.

Compared to established literature, experiments were performed at five orders of magnitude lower concentration of indicator, minimizing confounding effects of indicator on hydrodynamic motion. To accurately image the system, self-written MATLAB code was employed to enhance the color spectrum of experimental videos and images. A combination of two pH indicators was used to effectively isolate the wave front of the reaction system allowing for velocity measurements.

Utilizing experimental data, a simplified kinetics model was generated and a theoretical reaction rate constant was determined for the simplified model using a one-dimensional reaction diffusion solver written in MATLAB. The resulting rate constant of 3.6 x 105 M-2.5s-1 was then used to construct a two-dimensional numerical simulation in COMSOL 5.3a. This model was used to test validity of using the Boussinesq Approximation to treat these autocatalytic systems as incompressible rather than as compressible fluids.

Numerical simulations generated in COMSOL were able to accurately recreate chemo-hydrodynamic behaviors and wave velocities as measured experimentally. No detectable difference in results were determined between solving the system as incompressible with the Boussinesq Approximation compared to solving the full Navier-Stokes equations. However, there was a 20% time savings in solving the full Navier-Stokes equation compared to the simplified version. This result showed that when modeling these systems, computational efficiency was not saved by using the Boussinesq approximation. While these results were not different, larger or more complex systems may benefit from a full treatment of the Navier-Stokes equations rather than an approximation.

Rights

© 2021 Matthew Walter Eskew

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/35318

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