Evidence of Chaotic Mixing in the Alveolar Region of the Lung

TL;DR

This study combines experiments and simulations to demonstrate that asymmetry in alveolar wall motion induces chaotic mixing in the lung's acinar region, which is crucial for efficient particle transport.

Contribution

It introduces a model linking alveolar wall asymmetry to chaotic advection, revealing conditions that lead to chaotic mixing in the lung.

Findings

Asymmetry in wall motion is necessary for chaos.

Chaotic advection occurs within specific parameter ranges.

Most mammalian lungs operate near the chaotic regime boundary.

Abstract

We report an experimental and numerical investigation to study the role of asymmetry in the expansion-contraction of the acinar wall on the particle transport in the acinus. We model the acinar flow feature using a T-section by appropriately matching the dimensionless numbers to that in the acinus of healthy human subjects. We show that asymmetry in the expansion-contraction process (quantified by $\phi$) is required for chaotic advection. We show the stretch and fold process leading to chaos for a range of $\phi$ and scaled oscillation frequency $Sr$. We show a regime map in this generalize $\phi$ and $Sr$ space and show that most mammalian lungs fall at the boundary of chaotic regime.