Online

Curran, Kelly

Mechanical Engineering

2021

M.S.

Enhanced diffusion of a suspended particle in a porous medium has been observed when an oscillatory forcing has been imposed. The mechanism of enhancement, termed oscillatory diffusion, occurs when oscillating particles occasionally become temporarily trapped in the pore spaces of the porous medium, and are then later released back into the oscillatory flow. This thesis investigates the oscillatory diffusion process experimentally, stochastically, and analytically. An experimental apparatus, consisting of a packed bed of spheres subjected to an oscillatory flow field, was used to study the dynamics of a single particle. A variety of statistical measures were used and developed to characterize the diffusive process. A stochastic model was developed and showed great agreement with the experimental results. The experimentally validated stochastic model was then compared to an analytic prediction for diffusion coefficient from the continuous-time random walk (CTRW) theory for a range of physical and numerical parameter values. Good agreement between the stochastic model and CTRW theory was observed for certain ranges of parameter values, while differences of predictions are discussed and explained in terms of the assumptions used in each model. Results of the paper are relevant to applications such as nanoparticle penetration into biofilms, drug capsule penetration into human tissue, and microplastic transport within saturated soil.