Cuiyun Ou This email address is being protected from spambots. You need JavaScript enabled to view it.1,2, Hang Jian1,2, Qihong Deng3,4

1 School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou 510275, China
2 Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
3 School of Energy Science and Engineering, Central South University, Changsha 410083, China
4 XiangYa School of Public Health, Central South University, Changsha 410013, China


Received: February 19, 2020
Revised: August 24, 2020
Accepted: August 27, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

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Ou, C., Jian, H. and Deng, Q. (2020). Particle Deposition in Human Lung Airways: Effects of Airflow, Particle Size, and Mechanisms. Aerosol Air Qual. Res.


  • Minimum deposition efficiency exists for small particles (dp < 3 μm) in G3–G6 airways.
  • We defined the critical value as Reynolds number when inertial impaction dominates.
  • The critical value decreases with the increasing particle size.
  • Inertial deposition is merely affected by the Stokes number (St).
  • Gravitational sedimentation is mainly affected by the ratio of St to Re2.


Particle deposition in human lung airways is essential to understand the health effect of particulate air pollution. However, particle deposition in human lungs is rather complicated and its main influential factors are still unclear. A computational fluid dynamics (CFD) modeling was conducted to investigate the role of airflow (Re=100-2000) and particle size (1-10 μm) in the particle deposition in the human tracheobronchial airway model (G3-G6). According to the mechanism of particle deposition, the authors separated the deposition efficiency (DE) into two parts, one due to inertial impaction (DEi) and the other due to gravitational sedimentation (DEg). Particles are found to be uniformly distributed along tubes due to sedimentation, while particles are deposited in hot-spots around the bifurcations due to inertia. DEi increases rapidly with particle size but DEg increases log-linearly with particle size. Particles smaller than 2μm only deposit in deeper lung region where airflow rate is small, and 3μm particles deposit more in deeper region due to the combined mechanisms of gravitation and inertia, while larger particles mainly deposit in the proximal bifurcations due to inertial impaction. It is also found that inertial deposition is mainly affected by the Stokes number (), while gravitational sedimentation is mainly affected by the ratio of  and Re2. The change of human body orientation can influence the deposition patterns, except that the upright and lateral positions hold similar DE for 3 μm particles under all the inlet Re. The findings provide a precise Reynolds number when the deposition mechanism of a certain size particle shifts from gravitation to inertia.

Keywords: Inhalable particle; CFD simulation; Airflow pattern; Particle deposition; human body orientation; Deposition mechanisms.

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