A new capillary force model implemented in micro-scale CFD–DEM coupling for wet granulation

Abstract

A DNS (Direct Numerical Simulation) model for solid, liquid, and gas three-phase flow, mainly targeting to simulate the nucleation processes in wet granulation, is presented in this paper. A liquid–gas two-phase flow is solved by using the CIP (Constrained Interpolation Profile) method, which is one of the CFD multi-phase solvers, and a solid particle flow is solved by DEM (Discrete Element Method) separately. The interaction between fluid (liquid and gas) and solid phases is taken into account by coupling CFD and DEM. A new model is developed to account for the capillary force exerted on particles, i.e. the surface tension force which pulls a particle along with the solid–liquid–gas contact line, and the accuracy of the model is examined. Although the main focus in this study is to develop a CFD–DEM coupling and the capillary force models for wet granulation, some simulation results are also presented to see the droplet behaviour often encountered in a wet granulation process, i.e. the droplet penetration into a static particle bed as well as the droplet impingement onto a dynamic particle bed. The simulation results are compared with the experimental results in the literature and it shows a good agreement in terms of tendency.