Simulation of Red Blood Cell Migration in Small Arterioles: Effect of Cytoplasmic Viscosity

The dynamics of red blood cells in small arterioles are important as these dynamics affect many physiological processes such as hemostasis and thrombosis. However, studying red blood cell flows theoretically is challenging due to the complex shapes of red blood cells and the non-trivial viscosity contrast of a red blood cell. To date little progress has been made studying small arteriole flows (20-40µm) with a hematocrit (red blood cell volume fraction) of 10-20% and a physiological viscosity contrast. In this work, we present the results of large-scale simulations that show how the channel size, viscosity contrast of the red blood cells, and hematocrit effect cell distributions and the cell free layer in these systems. We utilize a massively-parallel immersed boundary code coupled to a finite volume solver to capture particle resolved physics in these systems. We show that channel size qualitatively changes how the cells distribute in the channel. Our results also indicate that at a hematocrit of 10% that the viscosity contrast is not negligible when calculating the cell free layer thickness. We explain this result by comparing lift and collision trajectories of cells at different viscosity contrasts.