Stable shapes of three-dimensional vesicles in unconfined and confined Poiseuille flow

TL;DR

This study uses numerical simulations to explore how viscosity contrast and confinement influence the shape and dynamics of 3D vesicles in Poiseuille flow, revealing phase diagrams and bistability phenomena.

Contribution

First to present phase diagrams for 3D vesicles with viscosity contrast in confined Poiseuille flow, highlighting the effects of confinement and viscosity contrast on vesicle behavior.

Findings

Confining walls push vesicles toward the center.

Viscosity contrast causes outward migration.

Bistability occurs at high capillary numbers.

Abstract

We use numerical simulations to study the dynamics of three dimensional vesicles in unconfined and confined Poiseuille flow. Previous numerical studies have shown that when the fluid viscosity inside and outside the vesicle is same (no viscosity contrast), a transition from asymmetric slippers to symmetric parachutes takes place as viscous forcing or capillary number is increased. At higher viscosity contrast, an outward migration tendency has also been observed in unconfined flow simulations. In this paper, we study how the presence of viscosity contrast and confining walls affect the dynamics of vesicles and present phase diagrams for confined Poiseuille flow with and without viscosity contrast. To our knowledge, this is the first study that provides a phase diagram for 3D vesicles with viscosity contrast in confined Poiseuille flow. The confining walls push the vesicle towards the center while the viscosity contrast has the opposite effect. This interplay leads to important differences in the dynamics like bistability at high capillary numbers.