Background: The flow of suspensions through bifurcations is encountered in several\napplications. It is known that the partitioning of particles at a bifurcation is different\nfrom the partitioning of the suspending fluid, which allows particle separation and\nfractionation. Previous works have mainly investigated the dynamics of particles suspended\nin Newtonian liquids.\nMethods: In this work, we study through 2D direct numerical simulations the partitioning\nof particles suspended in non-Newtonian fluids flowing in a T-junction. We\nadopt a flow configuration such that the two outlets are orthogonal, and their flow\nrates can be tuned. A fictitious domain method combined with a grid deformation\nprocedure is used. The effect of fluid rheology on the partitioning of particles between\nthe two outlets is investigated by selecting different constitutive equations to model\nthe suspending liquid. Specifically, an inelastic shear-thinning (Bird-Carreau) and a\nviscoelastic shear-thinning (Giesekus) models have been chosen; the results are also\ncompared with the case of a Newtonian suspending liquid.\nResults: Simulations are carried out by varying the confinement, the inlet flow rate\nand the relative weight of the two outlet flow rates. For each condition, the fluxes of\nparticles through the two outflow channels are computed. The results show that shear thinning\ndoes not have a relevant effect as compared to the equivalent Newtonian\ncase, i.e., with the same choice of the relative outlet flow rates. On the other hand, fluid\nelasticity strongly alters the fraction of particles exiting the two outlets as compared to\nthe inlet. Such effect is more pronounced for larger particles and inlet flow rates.\nConclusions: The results illustrated here show the feasibility to efficiently separate/\nfractionate particles by size, through the use of viscoelastic suspending liquids.
Loading....