Mechanism of margination in confined flows of blood and other multicomponent suspensions

TL;DR

This paper investigates the phenomenon of margination in blood flow, revealing that differential collision dynamics primarily drive the segregation of blood components near vessel walls, using simulations and stochastic modeling.

Contribution

It introduces a stochastic model that isolates the key mechanisms of margination, demonstrating the dominant role of collision dynamics in dilute suspensions.

Findings

Margination is mainly caused by differential collision dynamics.

Wall-induced migration plays a lesser role in dilute suspensions.

Heterogeneous collisions (s-f) significantly influence particle segregation.

Abstract

Flowing blood displays a phenomenon called margination, in which leukocytes and platelets are preferentially found near blood vessel walls, while erythrocytes are depleted from these regions. Here margination is investigated using direct hydrodynamic simulations of a binary suspension of stiff (s) and floppy (f) capsules, as well as a stochastic model that incorporates the key particle transport mechanisms in suspensions -- wall-induced hydrodynamic migration and shear-induced pair collisions. The stochastic model allows the relative importance of these two mechanisms to be directly evaluated and thereby indicates that margination, at least in the dilute case, is largely due to the differential dynamics of homogeneous (e.g. s-s) and heterogeneous (s-f) collisions