Three-dimensional free surface flow simulation of segregating dense suspensions

This paper presents a 3D numerical solution algorithm for the simulation of free surface flows of dense suspensions including particle migration phenomena. Segregation of the solid phase in processes such as powder injection molding and molding of semi-solid materials affects the rheology of the mixture and therefore the filling pattern. Segregation affects also the final properties and characteristics of such molded parts as a non-uniform particles distribution leads to non-uniform shrinkage, warpage and non-uniform mechanical properties. In this paper, particle migration is modeled using the diffusion flux model of Phillips et al. (Phys. Fluids A 1992; 4:30-40) and is extended to address 3D mold filling problems. The solution algorithm is validated against flow problems for which experimental and numerical data are available: circular Couette flow, piston-driven flow and sudden contraction-expansion flow. The particle migration model is then used to simulate mold filling problems in which the piston movement in the sleeve is known to induce particle migration. before the material enters the cavity. An arbitrary Lagrangian-Eulerian (ALE) formulation is developed and combined to a level-set front capturing method to simulate the piston movement and the evolution of the free surface in molding simulations. The ALE formulation is first compared with an Eulerian solution for the case of the piston-driven flow problem. The approach is then applied to injection molding problems to study the evolution of particle distributions during molding and in the final molded parts. Copyright (C) 2008 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.