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A Microfluidic Model of Biomimetically Breathing Pulmonary Acinar Airways
Published on: May 9, 2016
Hamiltonian chaos in a model alveolus
F S Henry1, F E Laine-Pearson, A Tsuda
1Molecular and Integrative Physiological Sciences, Harvard School of Public Health, Boston, MA 02115, USA.
Journal of Biomechanical Engineering
|December 3, 2008
Summary
Irreversible particle deposition in the lungs occurs due to chaotic mixing in alveoli, not just reversible flow. This chaotic fluid dynamics explains why fine particles remain in the pulmonary acinus after exhalation.
Area of Science:
- Pulmonary fluid dynamics
- Biophysics
- Computational fluid dynamics
Background:
- Airflow in the pulmonary acinus typically has a low Reynolds number, suggesting reversible flow.
- Despite this, fine particles are observed to deposit in the acinus, indicating irreversible behavior.
Purpose of the Study:
- To investigate the hypothesis that chaotic mixing in alveoli causes irreversible particle deposition.
- To numerically model and analyze fluid particle behavior in a rigid alveolated duct.
Main Methods:
- Numerical solution of incompressible, pulsatile flow equations in a rigid alveolated duct.
- Tracking fluid particles over multiple breathing cycles.
- Analysis of Poincare sections and Lyapunov exponents to identify chaotic behavior.
- Formulation of the streamfunction equation as a Hamiltonian system.
Main Results:
- Poincare sections revealed chains of islands and chaotic particle movement between them.
- The maximal Lyapunov exponent confirmed the presence of chaos.
- The streamfunction equation, when expanded, captured essential features of the Poincare sections.
- Hamiltonian dynamics theory confirmed chaos in the modeled flow.
Conclusions:
- Chaotic mixing in the alveoli is a significant factor contributing to irreversible particle retention in the pulmonary acinus.
- The study confirms the existence of chaos in airflow within a rigid alveolated duct, explaining particle deposition.
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