Red blood cells and other non-spherical capsules in shear flow: oscillatory dynamics and the tank-treading-to-tumbling transition

TL;DR

This paper studies the complex motion of red blood cells and similar microcapsules in shear flow, revealing various dynamic behaviors and a new transition between tank-treading and tumbling modes, which can help assess capsule properties.

Contribution

The study provides a comprehensive phase diagram for red blood cell dynamics and identifies a novel transition between tank-treading and tumbling at low shear rates.

Findings

Red blood cells exhibit tumbling, tank-treading, or intermittent motion depending on conditions.

A complete phase diagram for cell dynamics in shear flow is developed.

A new tank-treading-to-tumbling transition at low shear rates is identified.

Abstract

We consider the motion of red blood cells and other non-spherical microcapsules dilutely suspended in a simple shear flow. Our analysis indicates that depending on the viscosity, membrane elasticity, geometry and shear rate, the particle exhibits either tumbling, tank-treading of the membrane about the viscous interior with periodic oscillations of the orientation angle, or intermittent behavior in which the two modes occur alternately. For red blood cells, we compute the complete phase diagram and identify a novel tank-treading-to-tumbling transition at low shear rates. Observations of such motions coupled with our theoretical framework may provide a sensitive means of assessing capsule properties.