Kinetic Monte Carlo method applied to micrometric particle detachment mechanisms by aerodynamic forces

Abstract

The formulation of a kinetic Monte Carlo simulation to account for the different possible mechanisms present in the problem of resuspension of aerosol particles is addressed as an extension of a former model Benito et al (2016 J. Aerosol Sci. 100 26-37). The re-entrainment of micrometer particles to airflow when detached from a surface by aerodynamic forces is modeled using the similitude of the problem with the desorption process from heterogeneous surfaces. Depending on the relative role of the intervening forces, three main mechanisms for movement initiation can be present: rolling, sliding and lifting-off. Three different transition probabilities are defined for each mechanism and the corresponding transition rates calculated for the kinetic process to be simulated. The decisive factor for the development of the model is to set an appropriate dynamical hierarchy to simulate correctly the evolution of the transition rates as the airflow velocity increases, reflecting the stochastic nature of the process, not always fully captured by other Monte Carlo approaches. The model is applied to spherical and elongated particles on a flat surface, reproducing qualitatively well the experimental trends found by other authors for the case of particles with different shapes. It is also demonstrated that, for elongated particles, the main mechanism assisting the detachment is not rolling but sliding, underscoring the need for an adequate choice of the particles shape and detachment mechanism when looking for the critical conditions for particle removal from surfaces.