Three-dimensional Numerical Simulation of Gas-particulate Flow around Breathing Human and Particulate Inhalation

Our plain-English summary of Three-dimensional Numerical Simulation of Gas-particulate Flow around Breathing Human and Particulate Inhalation, by Y. Shimazaki, M. Okubo, T. Yamamoto (AIP Conference Proceedings, 2006).

The study

• Authors: Y. Shimazaki, M. Okubo, T. Yamamoto
• Journal: AIP Conference Proceedings
• Published: 2006;832(1):439-444
• Read it: PubMed · Publisher · Free full text

Abstract

It is important to predict the environment around the breathing human because inhalation of virus (avian influenza, SARS) is recently severe worldwide problem, and air pollution caused by diesel emission particle (DEP) and asbestos attract a great deal of attention. In the present study, three-dimensional numerical simulation was carried out to predict unsteady flows around a breathing human and how suspended particulate matter (SPM, diameter∼1 μm) reaches the human nose in inhalation and exhalation. In the calculation, we find out smaller breathing angle and the closer distance between the human nose and pollutant region are effective in the inhalation of SPM.

In plain English

This conference paper from Osaka Prefecture University described a three-dimensional computer simulation of air flow around a breathing person and of how tiny airborne particles reach the nose. Asbestos was mentioned only as one example of particulate air pollution. The model did not include asbestos fibers or any real people. The simulated person was 1.6 m tall and breathed only through the nose in a 4-second cycle. A thousand particles 1 µm across, which the authors called typical of bacteria and diesel emission particles, were placed in a box-shaped region near the person. With that region 0.1 m from the nose and a breathing angle of 0 degrees (measured from the vertical), particles first reached the nose after 7 s and 2.9% were captured. At that distance, none were captured at angles of 60 or 90 degrees. At a 30-degree angle, particles reached the nose when the source was 0.05, 0.1 or 0.2 m away but not at 0.3 m, with up to 2.6% captured at 0.05 m. The authors concluded that smaller breathing angles and closer sources led to more, and faster, particle capture.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Computer simulation (three-dimensional computational fluid dynamics model of air flow and particle motion); no human or animal subjects
• Who was studied: A computer model of a single breathing human, 1.6 m tall, in a 2.6 m by 2.0 m by 2.5 m space, breathing only through the nose with a sinusoidal 4.0 s breathing cycle
• Exposure: A thousand simulated particles 1 µm in diameter with a printed density of 10 kg/m3, described as typical values for bacteria and diesel emission particles (DEP), placed randomly in a box region at a set distance from the nose. Breathing angles of 0, 30, 60 and 90 degrees were tested with the source 0.1 m away. Source distances of 0.05, 0.1, 0.2 and 0.3 m were tested at a 30-degree breathing angle. Asbestos fibers were not modeled.
• Main results:
  • With a breathing angle of 0 degrees and the source 0.1 m away, particles reached the nose in 7 s at the earliest and the captured efficiency was 2.9%, the highest among the angles tested at that distance
  • With the source 0.1 m away, no particles were captured at breathing angles of 60 degrees or larger
  • At a breathing angle of 30 degrees, particles reached the human at source distances of 0.05, 0.1 and 0.2 m but not at 0.3 m
  • At a 30-degree breathing angle, the highest captured share across the source-distance runs was 2.6% of particles, at a source distance of 0.05 m
  • Exhalation affected the flow field more than inhalation, and in all simulations particles were drawn from the region above the person
• The authors' conclusion: The authors concluded that the particle captured efficiency tends to be higher, and particles tend to reach the nose faster, as the breathing angle becomes smaller and as the source distance becomes closer to the body

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