On the complex dynamics of a red blood cell in simple shear flow

TL;DR

This paper develops an analytical model to understand how red blood cell deformability influences its complex motion in shear flow, explaining transitions between tumbling and swinging behaviors.

Contribution

It introduces a theoretical framework for nearly-spherical visco-elastic particles in shear flow, clarifying the role of deformability in dynamic transitions.

Findings

Deformability affects the transition from tumbling to swinging.

Intermittent behavior occurs only with fixed shape particles.

Comparison reveals limitations of fixed-shape phenomenological models.

Abstract

Motivated by the reported peculiar dynamics of a red blood cell in shear flow, we develop an analytical theory for the motion of a nearly--spherical fluid particle enclosed by a visco--elastic incompressible interface in linear flows. The analysis explains the effect of particle deformability on the transition from tumbling to swinging as the shear rate increases. Near the transition, intermittent behavior is predicted only if the particle has a fixed shape; the intermittency disappears for a deformable particle. Comparison with available phenomenological models based on the fixed shape assumption highlights their physical foundations and limitations.