Vesicle Dynamics in a Confined Poiseuille Flow: From Steady-State to Chaos

TL;DR

This study investigates vesicle behavior in confined Poiseuille flow, revealing a transition from steady shapes to chaotic dynamics influenced by confinement and flow strength, highlighting complex elasticity-driven phenomena in laminar flow conditions.

Contribution

The paper provides a comprehensive phase diagram of vesicle dynamics under confinement and flow strength, demonstrating the transition from steady states to chaos, which advances understanding of RBC-like behavior in microflows.

Findings

Vesicles exhibit steady parachute and slipper shapes.

Chaotic vesicle dynamics emerge through multiple periodic oscillations.

Flow can become effectively turbulent due to vesicle elasticity.

Abstract

Red blood cells (RBCs) are the major component of blood and the flow of blood is dictated by that of RBCs. We employ vesicles, which consist of closed bilayer membranes enclosing a fluid, as a model system to study the behavior of RBCs under a confined Poiseuille flow. We extensively explore two main parameters: i) the degree of confinement of vesicles within the channel, and ii) the flow strength. Rich and complex dynamics for vesicles are revealed ranging from steady-state shapes (in the form of parachute and slipper) to chaotic dynamics of shape. Chaos occurs through a cascade of multiple periodic oscillations of the vesicle shape. We summarize our results in a phase diagram in the parameter plane (degree of confinement, flow strength). This finding highlights the level of complexity of a flowing vesicle in the small Reynolds number where the flow is laminar in the absence of vesicles and can be rendered turbulent due to elasticity of vesicles.