# Dynamics of a large population of red blood cells under shear flow

## TL;DR

This paper provides a comprehensive analysis of red blood cell dynamics under shear flow, considering cell variability, fluid viscosity effects, and transition behaviors, with implications for understanding blood flow mechanics.

## Contribution

It offers a detailed description of red blood cell motions under shear flow, including the effects of viscosity and cell property dispersion, which are rarely addressed together in experimental studies.

## Key findings

- Identification of stable and unstable cell motions using Jeffery orbits.
- Observation of hysteresis in cell motion transitions.
- Dependence of transition thresholds on flow stress and fluid viscosity.

## Abstract

An exhaustive description of the dynamics under shear flow of a large number of red blood cells in dilute regime is proposed, which highlights and takes into account the dispersion in cell properties within a given blood sample. Physiological suspending fluid viscosity is considered, a configuration surprisingly seldom considered in experimental studies, as well as a more viscous fluid that is a reference in the literature. Stable and unstable flipping motions well described by Jeffery orbits or modified Jeffery orbits are identified, as well as transitions to and from tank-treading motion in the more viscous suspending fluid case. Hysteresis loops upon shear rate increase or decrease are highlighted for the transitions between unstable and stable orbits as well as for the transition between flipping and tank-treading. We identify which of the characteristic parameters of motion and of the transition thresholds depend on flow stress only or also on suspending fluid viscosity.