Electronic Theses and Dissertations Archive

Date

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Committee Chair

Ranganathan Gopalakrishnan

Committee Member

Alexander Headley

Committee Member

Daniel Foti

Committee Member

Nathan DeYonker

Abstract

Understanding the dynamics of charged and neutral particles in gaseous environments is important to a wide range of physical, chemical, and atmospheric processes. In this work, I present two complementary computational studies: one focused on Mutual Neutralization (MN) reactions, and the other on the rotational Brownian motion of aerosol particles with arbitrary shapes. Both efforts emphasize high-fidelity physical modeling through rigorous numerical and theoretical approaches. In the first study, the rate constants of mutual neutralization (MN) reactions are calculated self-consistently by incorporating the electron transfer probability, using Landau-Zener state transition theory with inputs derived from ab initio quantum chemistry calculations, into classical trajectory simulations. It is seen that the accurate electronic structure calculation results in excellent agreement between simulation results and available experimental data within a factor of ~2 or ~±50%. The second study addresses the rotational dynamics of aerosol particles undergoing Brownian motion, where particle shape critically influences aerodynamic, charging, and optical properties. An explicit time-stepping procedure is presented to simulate the rotational Brownian motion of arbitrary shaped aerosol particles by solving Euler’s equation of rotation. A Langevin formulation of the rotation equations is used, wherein Brownian motion due to thermal collisions between a particle and background gas molecules is represented using a stochastic fluctuating torque and fluid resistance is included as a drag torque. Numerical solutions to rotation under torque-free conditions, deterministic rotation, and stochastic rotation for arbitrary shapes are discussed. The presented method enables time-resolved simulation of Brownian rotation for direct comparison with experimentally measured trajectories or statistical measures. The second order accuracy of the used time-stepping procedure places a severe restriction on the timestep that can be used for obtaining accurate results. Together, these studies contribute to a better understanding of microscopic particle dynamics in gaseous medium by combining electronic structure calculations with stochastic simulations for practical and theoretical applications in fields such as plasma physics, aerosol science, and nanotechnology.

Comments

Data is provided by the student.”

Library Comment

Dissertation or thesis originally submitted to ProQuest/Clarivate.

Notes

Open Access

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