(408d) Cross-Stream Distribution and Dynamics of Red Blood Cells in Sickle Cell Disease

Diseased red blood cells (RBCs) in patients suffering from sickle cell disease (SCD) display substantially different physical properties than do healthy RBCs. Chronic complications such as endothelial dysfunction are associated with SCD, for reasons that are unclear. We hypothesize that in SCD, sickle RBCs, which are considerably stiffer than healthy RBCs, marginate towards the vessel walls and exert repeated damage to the endothelium, causing endothelial dysfunction as a consequence. Direct numerical simulations are performed to investigate both the dynamics of a flowing binary suspension of deformable biconcave discoids and stiff curved prolate spheroids representing healthy and sickle RBCs, respectively, and the orbital behavior of single sickles in shear flow. In the suspension, the key observation is that the sickles exhibit a strong margination towards the walls. At steady state, the deformable biconcave discoids tend to undergo a rolling motion, while the stiff sickles behave like rigid bodies and undergo a kayaking or rolling motion. For single sickles, a Jeffery-like quasiperiodic orbit is taken at long times regardless of the initial orientation, and the average of the long-time trajectory can be well approximated using the analytical solution for Jeffery orbits. As the capsule becomes more deformable or curved, the orbit shifts towards rolling, and this feature holds qualitatively as the viscosity ratio between the inner and outer fluids increases from 1 to 5.