Representation of capillary forces in polydisperse granular assemblies in the pendular regime

In this paper, the equations governing capillary forces between polydisperse spheres in the pendular regime are presented. These equations are adopted within the Laplace-Young framework using a Toroidal approximation of the liquid bridge geometry. Based on the numerical solution of the fundamental problem and a novel evolutionary computing technique (EPR), an analytical expression is developed for the prediction of capillary force. The analytical expression accounts for the effects of intrinsic parameters such as inter-particle separation distance, ratio of particle radii and liquid volume. Such a representation of capillary forces is shown to mimic the real behaviour with a good accuracy. The developed model can be implemented in discrete element computer simulations as it does not require any iterations to update contact forces at particle level.