A square-force cohesion model and its extraction from bulk measurements

Accurate modeling of interparticle forces in DEM is critical to predicting the rheology of cohesive particles. Rigorous cohesion models usually include parameters associated with particle surface roughness. However, both roughness measurement and its distillation into appropriate model parameters remain challenging. We propose a square-force cohesion model, where cohesive force remains constant until a cutoff separation, above which cohesion vanishes. We demonstrate the square-force model is a valid surrogate of more rigorous models. Specifically, when two parameters of square-force model are chosen to match the two key quantities governing dense and dilute flows, namely maximum cohesive force and critical cohesive energy, respectively, DEM results using square-force and more rigorous models show good agreement. For practical application of the square-force model to lightly cohesive systems, a method is established to extract its parameters via defluidization, enabling determination of particle-particle cohesion from simpler bulk measurements than complicated and expensive scans on individual grains. (c) 2018 American Institute of Chemical Engineers AIChE J, 64: 2329-2339, 2018