Microstructure and Rheology of Semi-Dense and Dense Suspensions in Confined Flows*

In this work, Core-Modified Dissipative Particle Dynamics, CM-DPD, is employed to model the flow and microstructure development of semi-dense and dense suspensions under confinement. The walls as well as the solvent are represented as traditional DPD particles which interact center-to-center by soft potentials. Colloidal particles, on the other hand, are modelled as CM-DPD particles, having a rigid core and a soft shell and the interactions are driven by a semi-hard potential. Colloidal particles interactions take place by means of a core force, responsible to tune the rigidity, and a lubrication force, representative of the short-range hydrodynamic interactions.  In this work, the effect of flow rate, confinement and particle rigidity were systematically studied in semi-dense and dense suspensions in a pressure driven flow. At stronger confinement ratios, lower rigidity and weaker flow strengths the overall particles velocity tends do decrease. Rigid particle suspensions are more viscous and have a slower motion compared to the soft ones. Additionally, rigidity leads to opposite migration effects. Different microstructures and particles arrangement were observed depending on the values of the parameters adopted, with confinement and particle rigidity being the most important factors driving particle migration and clustering.