Abstract
Diffusion-induced swelling or shrinkage of particles is ubiquitous in many industrial processes and nature. Aiming to rigorously model these deformable particles, a microscopic model that considers the microstructural evolution of individual particles is developed for the first time and implemented into the discrete element method (DEM), which is experimentally validated. The robustness of this model is also evaluated by comparing its performance with a macroscopic diffusion-induced swelling model and a phenomenological swelling model. The swelling behaviours of a single particle and particle beds of various configurations in water are then analysed. It is shown that the microscopic swelling model and the phenomenological swelling model can better describe the swellings of single particle and particle beds than the macroscopic swelling model. Moreover, the microscopic swelling model can not only reproduce the phenomena of volume expansion of particles but also well predict the microstructural evolution of individual particles, as observed experimentally. Furthermore, the microscopic swelling model is capable of describing the shrinkage processes and the particle-particle diffusions of swellable particles. It is hence demonstrated that DEM with the microscopic swelling model, which captures the microscopic physical mechanisms of particle swelling and the microstructural change of swelling particles, could be a useful tool for modelling swellable granular materials in various industrial processes.