Publication Cover
Inhalation Toxicology
International Forum for Respiratory Research
Volume 22, 2010 - Issue 8
340
Views
23
CrossRef citations to date
0
Altmetric
Research Article

Flow in a terminal alveolar sac model with expanding walls using computational fluid dynamics

&
Pages 669-678 | Received 04 Dec 2009, Accepted 04 Mar 2010, Published online: 13 May 2010
 

Abstract

Particles depositing on alveolar walls is of concern due to their potential to migrate through the blood-gas barrier. Whole-lung dosimetry models do not account for the flow field inside the alveoli and therefore may not accurately describe alveolar deposition. Studies that quantify the flow patterns in realistic geometries are limited and results inconsistent. This study aims to better understand the fluid characteristics in the terminal air sacs; specifically, alveolar mouth to depth flow rate ratio, penetration depth of residual air, and diffusive versus convective particle motion. A terminating alveolar sac with expanding alveolar walls was constructed using 13 truncated sphere-shaped alveoli, with dimensions consistent with published morphometry data. The flow field was governed by a measured in vivo breathing curve for normal volumes over periods of 2 and 4 seconds, analyzed numerically and compared to previous literature. Recirculation was not present, consistent with prior studies. Flow rate ratios (0.18–0.36) were within the range (0.057–1) previously reported. Penetration depths were less than 33% into the air sac during inhalation, decreasing in length for air inside the sac to zero near the wall. Péclet numbers indicated diffusion dominated flow for all submicron-sized particles. However, convection was significant at the duct entrance for particles >0.5 micron and inside the sac for particles >1 micron. Wall motion induced convection may not always be negligible, and if neglected could affect the accuracy of deposition predictions for certain particle sizes and flow conditions.

Acknowledgments

The authors would like to thank Dr. Kambiz Nazridoust (Division of Computational Biology, Hamner Institutes for Health Sciences) for contribution in developing the computer code used for simulating breathing and Ryan Lewis (Application Consultant Specialist, Research Computing, RIT) and Paul Mezzanini (Senior Systems Administrator, Research Computing, RIT) for providing support to their various computational resources.

Declaration of interest

This work was completed with the support of the American Cancer Society (RSG-05-021-01-CNE).

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.