# Numerical simulation of red blood cells migration and platelets margination for blood flow in micro-vessels with fusiform aneurysms

## TL;DR

This study uses simulations to explore how red blood cells and platelets behave in blood vessels with aneurysms, showing how these behaviors affect blood flow and oxygenation.

## Contribution

The study provides new insights into blood cell dynamics in micro-vessels with fusiform aneurysms using numerical simulations.

## Key findings

- Decreasing hematocrit increases migrated red blood cells and cell-free layer thickness, affecting blood viscosity and wall shear stress.
- Fusiform aneurysms reduce red blood cell velocity by over 83%, potentially impairing oxygenation.
- The cell-free layer is thinner at the divergent part of the aneurysm, showing an asymmetrical trend in blood flow dynamics.

## Abstract

Understanding several micro-vascular diseases depends mainly on examining the dynamic behavior of blood cells, especially the red blood cells (RBCs) and platelets. For instance, the dynamics of RBCs and platelets are significantly impacted by micro-vascular diseases such as aneurysms, which may lead to many disorders. The oxygenation process, for example, depends on the motion and velocity of the RBCs. Important hemodynamic parameters such as the wall shear stress (WSS) and the cell-free layer (CFL) thickness are affected by the motion of the RBCs and platelets. Thus, the main objective of the current study is to introduce more insights into cellular blood dynamics in micro-vessels with fusiform aneurysms, which have important clinical implications, by examining some important hemodynamic parameters. This study examines the migration of RBCs and their velocities under different hematocrit levels. Furthermore, the effect of hematocrit variation on platelets’ margination, the CFL, and the WSS is investigated. The simulations are performed using a validated code developed cellular flow simulations. The obtained results show that decreasing the hematocrit value increases the proportion of migrated RBCs, and hence the CFL thickness increases, which significantly affects blood apparent viscosity, especially at the aneurysm zone, and hence affects the local WSS and the endothelial cell in the vessel wall tissue. In addition, it is found that the fusiform aneurysm reduces the velocity of the RBCs by more than 83%, which can affect the oxygenation process. The obtained results exhibit an asymmetrical trend up and downstream of the aneurysm zone, with a thinner CFL at the divergent part of the aneurysm. These results are beneficial for medical microfluidic devices as well as for understanding many microvascular diseases.

The online version contains supplementary material available at 10.1038/s41598-025-22429-w.