Effect of micro-vessel stenosis severity and hematocrit level on red blood cell dynamics and platelet margination: A numerical study

Understanding many micro-vascular diseases is aided by examining the dynamical behavior of blood cells. For instance, micro-vascular stenosis significantly influences the dynamics of red blood cells and hence causes several micro-vascular disorders. Thus, the objective of the current study is to numerically simulate cellular blood flow in stenosed micro-vessels with different stenosis severities and hematocrits to examine hemodynamic features which have important clinical implications. Red blood cells' migration, velocity, and deformation are predicted. Furthermore, platelets' margination and cell-free layer formation are examined. Accordingly, a three-dimensional numerical simulation of blood cells and their interaction with the surrounding plasma is considered. The simulation is performed using a validated code developed for cellular blood flows. Red blood cells' migration and platelets' margination are confirmed, which enhances the validity of the code. The obtained results report a high dependence of red blood cells' migration and platelets' margination on the hematocrit level, which agrees with other published studies. An asymmetrical cell-free layer thickness is exhibited along the stenosed vessel, with a maximum value at the throat of the stenosis, which greatly affects blood apparent viscosity and induces plasma skimming in this region. In addition, it is found that the cell-free layer thickness is strongly linked to stenosis severity and the hematocrit level. Due to its role in the endothelial cells' function and structure, the wall shear stress is estimated. A reduction more than 75 % in the wall shear stress is obtained due to stenosis, with maximum values at the throat compared with the healthy case. The Fahraeus effect is examined, and the obtained results are compared with published experimental and computational works with an acceptable degree of agreement.