Core-Shell particles are commonly used materials in chromatography. In this study, a mathematical model that mimics diffusion around Core-Shell particles was developed. A random-walk based algorithm was implemented to simulate diffusion and a Core-Shell particle geometry was computationally formed, based on simple geometric constructs and relations. Diffusion simulations were carried out on a randomly packed geometry formed from these particles. The behavior of time-dependent diffusivity data obtained from the model was found to be consistent with prior literature data from nuclear magnetic resonance experiments where transient diffusivity of a self-diffusing substance was measured in porous media.