Abstract
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.