(199d) Simulation of Powder Flow in Die Filling Applications

Weight uniformity of tablets in die filling applications is proportional to the consistency of the powder stress distribution and the flow of the powder in the feed frame of a die fill. Therefore, understanding the stress distribution profiles within a feed frame appears to be the key factor for optimal design of the die fill in terms of feeder paddle geometry and compression speed. Recently, discrete element methods have been quite frequently used for powder flow application. Although they are rather accurate in predicting particle-particle interactions, the discrete element methods are severely limited by maximum number of tracked particles and thus are limited to a relatively small domain size. On the contrary, the Eulerian-based models are independent of the number of particles but the implementation of frictional forces is indirect and not well understood. Therefore, Lagrangian-based Particle-In-Cell techniques, which can be used to track a relatively small number of particles while maintaining the ability to model the contact forces directly, appear the most suitable choice for powder flow analysis. In the current study, we compare numerical predictions of Eulerian granular and Particle-In-Cell models that have been developed in commercial CFD software Fluent 12. Numerical results obtained by the models are validated against experimental data at different flow conditions.