Simulation of microstructure/mechanism relationships in particle deposition

Abstract

The important connection between particulate deposit properties and deposition mechanism remains poorly understood and only scarcely studied. Accordingly, in this research, we develop a discrete stochastic model to simulate particulate deposition processes resulting from realistic combinations of deposition mechanisms. Particle motion is assumed to be determined by the superposition of a deterministic force that acts toward the collecting surface and a random force, which produces Brownian diffusion. We characterize the resulting deposit microstructure via porosity and pore sizelarea distribution, surface area; and we examine the evolution of these descriptors with time (number of particles deposited) for different deposition mechanisms. We also examine the effect of particle polydispersity, spatial orientation (for nonspherical particles), and mean-free-path on the resulting deposit structure.

Aerosol Processing of Materials

“…Rosner and co-workers (Park and Rosner, l989a, b;Tassopoulos et al, 1989;Rosner and Tassopoulos, 1991;Castillo et al, 1991Castillo et al, , 1992 have done extensive studies on inertial and thermophoretic effects on formation and transport of aggregates in highly loaded aerosol systems. Tassopoulos et al (1989) extended the ballistic aggregation and diffusion-limited aggregation models (Witten and Sander, 1981;Family and Landau, 1984;Meakin et al, 1986) to develop a discrete stochastic model simulating the growth and microstructures of aggregates in two-and three-dimensions by several mechanisms, namely, Brownian diffusion, impaction, and phoresis ithermophoresis, photophoresis, or electrophoresis), occurring simultaneously.…”

“…Tassopoulos et al (1989) extended the ballistic aggregation and diffusion-limited aggregation models (Witten and Sander, 1981;Family and Landau, 1984;Meakin et al, 1986) to develop a discrete stochastic model simulating the growth and microstructures of aggregates in two-and three-dimensions by several mechanisms, namely, Brownian diffusion, impaction, and phoresis ithermophoresis, photophoresis, or electrophoresis), occurring simultaneously. However, this work lacked iterative comparisons of predictions from the model and experimentally observed aggregate microstructures.…”

“…However, this work lacked iterative comparisons of predictions from the model and experimentally observed aggregate microstructures. Although the model considered the effects of particle polydispersity, mean-free-path, and spatial orientation (for nonspherical particles), it had no provisions to incorporate certain situations encountered in practice, such as aggregate growth for which the deposition mechanisms evolve with time or aggregates which gradually evolve due to, say, sintering (Tassopoulos et al, 1989).…”

A Potential Soot Mass Determination Method from Resistivity Measurement of Thermophoretically Deposited Soot

“…Therefore no quantitative estimates of the film porosities were made and it is difficult to say whether the porosity increases or decreases with agglomerates size. This might be the case when two opposing factors of Brownian diffusion and thermophoresis affect the building of microstructure and resulting deposition properties (Tassopoulos et al 1989). One such property is porosity, that can influence the thermal and electrical conductance across the particle film, which is sensitive function of mean free path and in case of its larger value; the deposition properties may behave like in ballistic regime resulting in compact deposits.…”

Numerical study on sedimentation behavior of solid particles used as simulant fuel debris

“…To understand the particle sedimentation and its evolution during the settling process, different semidynamic numerical models such as the sticking model [11], discrete stochastic model [12], and kinetic forcebalance model [13] can be used. As the inter-particle forces in these models are either ignored or treated based on assumptions, these models might be inappropriate to study the effects of the forces on bed formation during particle sedimentation process.…”