Particle inhalability of a standing mannequin with large airways in a ventilated room

Mehrdad Azhdari; Mohammad Mehdi Tavakol; Goodarz Ahmadi

doi:10.1016/j.compbiomed.2021.104858

Particle inhalability of a standing mannequin with large airways in a ventilated room

Comput Biol Med. 2021 Nov:138:104858. doi: 10.1016/j.compbiomed.2021.104858. Epub 2021 Sep 10.

Authors

Mehrdad Azhdari¹, Mohammad Mehdi Tavakol², Goodarz Ahmadi³

Affiliations

¹ Department of Mechanical Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran.
² Department of Mechanical Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran. Electronic address: tavakolmm@shirazu.ac.ir.
³ Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY, USA.

PMID: 34560501
DOI: 10.1016/j.compbiomed.2021.104858

Abstract

This study presents a series of numerical simulations for airflow field and particle dispersion and deposition around a mannequin inside a ventilated room. A 3-D airway system of a volunteer subject with a large respiratory system was reconstructed from the nostril inlet to the end of the tracheobronchial tree 4th generation and was integrated into a standing mannequin at the center of a room. The room ventilation system supplied air through a diffuser and expelled air via a damper in three modes. The airflow field was first evaluated by solving the governing equations and the k-ω SST transitional turbulence model using the Ansys-Fluent software. Then spherical particles with various diameters were released into the room, and their trajectories were evaluated using the Lagrangian approach. Aspiration fraction and particle deposition for inhalation flow rates of 15 and 30 L/min were analyzed using a modified discrete random walk (DRW) stochastic model using a user-defined function (UDF) coupled to the Ansys-Fluent discrete phase model. For the first ventilation mode, a recirculation flow region formed behind the mannequin that led the airflow streamlines to the breathing zone. A recirculation flow formed in front of the face for the second ventilation mode that led the airflow streamlines out of the mannequin breathing zone. For the third mode, however, there was no strong recirculation flow zone around the mannequin. Simulation results showed that the aspiration fraction in the first ventilation mode was higher than the other modes. In addition, the regional deposition rates and deposition patterns of particles inside the respiratory system were presented for each region. Accordingly, most large particles were trapped in the nasal passage; however, some large particles penetrated deeper into the airway due to the large airway size. For the higher breathing rate, the percentage of large escaped particles from the lobe branches dropped by a factor of 7 compared to the lower breathing rate.

Keywords: Airway; Aspiration fraction; Large airway; Particle deposition; Standing mannequin; Ventilation system.

MeSH terms

Bronchi
Computer Simulation
Humans
Manikins*
Particle Size
Respiration*