Crossover from tumbling to tank-treading-like motion in dense simulated suspensions of red blood cells

TL;DR

This study uses computer simulations to show that red blood cells transition from tumbling to tank-treading motion at high shear rates, regardless of cell concentration or deformability, linked to a stress ratio crossing a critical threshold.

Contribution

It demonstrates that the tumbling-to-tank-treading transition occurs at high volume fractions and is governed by a stress ratio, independent of cell deformability and concentration.

Findings

Transition occurs at a specific stress ratio, independent of volume fraction.

Cell deformation scales with shear stress, showing no signature of the transition.

Collective effects do not alter the critical stress ratio for the transition.

Abstract

Via computer simulations, we provide evidence that the shear rate induced red blood cell tumbling-to-tank-treading transition also occurs at quite high volume fractions, where collective effects are important. The transition takes place as the ratio of suspension stress to the characteristic cell membrane stress exceeds a certain value, independent of volume fraction and cell deformability. This value coincides with that for a transition from an orientationally less ordered to a highly ordered phase. The average cell deformation does not show any signature of the transition, but rather follows a simple scaling law independent of volume fraction.