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Flow Characterization in Healthy Airways and Airways with Chronic Obstructive Pulmonary Disease (COPD) during Different Inhalation Conditions

Category: Air Pollution Modeling

Volume: 18 | Issue: 10 | Pages: 2680-2694
DOI: 10.4209/aaqr.2018.06.0232
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Justus Kavita Mutuku1, Wei-Hsin Chen 2,3

  • 1 Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan
  • 2 Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan
  • 3 Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 70101, Taiwan

Highlights

Flow behaviors in healthy airways and airways with COPD are predicted numerically.
Real breathing curves at rest, light activity, and moderate activity are applied in the study.
Dean vortices in airways due to induced centrifugal force are observed.
Maximum velocity between geometry variation and minor loss competition is outlined.
Pressure drop affected by COPD is 3.38 Pa for rest and 21.39 Pa for moderate exercise.


Abstract

The flow of air in the central and lower generations of the human airways results in complex secondary flows, which heavily affect the deposition of aerosol such as PM2.5 in the human airways. To figure out the flow dynamics in healthy airways and airways with chronic obstructive pulmonary disease (COPD), the flow distributions were predicted numerically. In a bronchial tube geometry (G5-G8), COPD was represented by an axisymmetric constriction in G6-2 of a four-generation airway. Real and unsteady breathing inhalation curves under rest, light activity, and moderate exercise were applied in the simulations. The velocity distribution, recirculation, and stagnation zones in the generation G6-2 affected by COPD together with the effects of sudden pressure drop in the constriction were investigated. Two symmetrical vortices (Dean vortices) were formed at the cross-sections of the geometry affected by COPD and their intensities were dependent on the Reynolds number. The mas flow rates in the healthy generation (G6-1) went to as high as 3.10 times the mass flow rate in the generation affected by COPD (G6-2). The simulations showed that inflammation of the bronchus greatly affected pressure distribution and the rates of mass flow in the human airway during inhalation. The overall pressure drop in the bifurcation affected by COPD was 3.38 Pa for rest, 10.91 Pa for light activity and 21.39 Pa for moderate exercise. A combination of these factors make COPD patients very susceptible to adverse health effects caused by inhalation of PM2.5.

Keywords

Airway Chronic obstructive pulmonary disease (COPD) Computational fluid dynamics (CFD) Pressure drop Dean vortices Secondary flow


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