(422a) Lattice Kinetic Monte Carlo Simulations of Aggregation and Fragmentation Processes in Flow
The aggregation and fragmentation of molecular and cellular species in the presence of flow are important in a variety of industrial and biological processes ranging from aerosol formation to platelet aggregation. These processes have been generally described with continuum population balance equations (PBEs) based on aggregation/fragmentation kernels which depend on the flow characteristics and morphology of the aggregates. Although aggregation kernels are easily defined for simple flows, they are generally impossible to derive for the complex flows found in realistic conditions. Microscopic models such as molecular dynamics can readily account for complexity in the flow field as well as the molecular interactions that determine individual aggregation or fragmentation events, because these methods explicitly consider all molecules in the system. The computational cost, however, is usually prohibitive for simulating time scales over many aggregation or fragmentation events. Mesoscopic models such as kinetic Monte Carlo, Brownian dynamics  and others, provide a bridge between PBEs and microscopic models by coarse-graining molecular motion while retaining spatial and morphological information.
Here, we present a new approach based on the lattice kinetic Monte Carlo (LKMC) method to address this class of problems. Recently, we reported an LKMC algorithm which allows the incorporation of both convective and diffusive particulate transport for arbitrary particle concentration, although no aggregation was considered . Here, we extend this algorithm to include particle-particle coalescence and therefore a distribution of particle sizes in the presence of arbitrary flow. Detailed comparisons are made to well-known solutions of PBEs with respect to different aggregation kernels and lattice discretization. Solutions for more complex systems are discussed in the context of arbitrary flows, sticking coefficients, fragmentation, particle morphologies, and applications for platelet aggregation.
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