Dynamics and rheology of red blood cell (RBC) suspensions in confined Poiseuille flows are studied numerically using simplified vesicle and capsule models. By using periodic boundary conditions along flow direction, the RBC and its images are forced to align to the same lateral position, showing a single file with equal interdistance. Lateral migration of RBC is analyzed by increasing RBC concentration $\varphi$ (defined as the area or volume fraction occupied by RBCs). A scaling law for the migration velocity as a function of RBC concentration is proposed. The intrinsic viscosity $\left[\eta \right]$ (the contribution of each RBC on effective viscosity) shows a nontrivial property with the increase of RBC concentration $\varphi$, due to the spatial organization of RBCs. We find that the overall behavior of the periodic suspension shares the same features as those obtained for a suspension for which the periodicity along the flow line is relaxed. For the periodic suspension the computational time is greatly reduced as compared to a situation without imposing periodicity. This study offers an interesting perspective for the study of concentrated suspension, not only for a single file but also for more complex structures, where in each periodicity more than a single RBC is considered. These findings can help understanding the behaviors of blood flow in microcirculation with a highly reduced computational cost.

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• Applications of soft matter
• Biological fluid dynamics
• Fluid-particle interactions
• Vesicle structures