(38c) Monte Carlo Modeling of Polydisperse Granular Systems

Most practical applications of granular media entail a polydisperse particle distribution. As such, it is vital that any simulation method for granular flows accurately reproduce the distinct phenomena associated with polydispersity, such as size segregation and its impacts on bed expansion. The mixture of particle sizes introduces considerable difficulty in determining the solid stress tensor of a granular flow. Discrete simulation methods are able to accurately characterize these effects, but are more computationally expensive. By contrast, more efficient continuum methods must rely on empirical closures to the stress tensor which become less reliable for polydisperse systems. The Energy Direct Simulation Monte Carlo (EDSMC) method has been shown to accurately simulate both qualitative and quantitative results for monodisperse fluidized systems. Additionally EDSMC's basis in Chapman-Enskog theory allows for more robust stress calculations compared to continuum models, while retaining much of the computational efficiency. However, its capabilities regarding polydispersity have yet to be demonstrated. The results of EDSMC simulations for various polysidsperse species in the fast fluidization regime are presented and compared to monodisperse distributions under the same conditions. Key metrics such as size segregation and elutriation, pressure drop, and bubble formation patterns are shown and measured against both empirical data and DEM simulations. Additionally, the impact of the real-to-simulated particle ratio on these systems is assessed and the computational benefits of this parameter are explored for the simulated systems.