<p class="MsoNormal" style="text-align: justify">In this study, the dispersion of spherical particles inside a room and around a sleeping mannequin model was investigated numerically. The respiratory tract model was prepared by CT scan image processing and was attached to a lying mannequin in the middle of the room. The respiratory system was constructed from the nostril to the trachea. The thermal plume structure around the mannequin formed due to the difference between the ambient air temperature and the mannequin surface temperature was simulated. For turbulence modeling, the RNG k-ε model was adopted and used in the Ansys-Fluent 19 software. Lagrangian particle tracking method with an appropriate stochastic model was employed to study dispersion and deposition of spherical particles in the room and around the mannequin for the steady inhalation rate of 7.5 lit/min. Unit density 5, 10, 20, 50, and 100 µm spherical particles were released, and their trajectories inside the computational domain were tracked using the Ansys-fluent discrete phase model. The aspiration efficiency of spherical particles and their subsequent deposition at different parts of the respiratory tract were studied and compared with the case of a standing mannequin with the same geometry under identical environmental conditions.</p><p>Two different cases were considered for the numerical simulations. In the first case, the mannequin surface temperature was higher than the surrounding air temperature, and the thermal plume around the mannequin was upward. The second case focused on the downward thermal plume around the mannequin when the mannequin surface temperature was lower than the surrounding air temperature. &nbsp;Simulation results were presented for the structure of the airflow pattern around the mannequin and aspiration of particles. For the first case with the upward thermal plume, the aspiration efficiency of particles increases by increasing the particle size from 5 to 20 microns, and then the reverse trend was observed for larger particles. For the second case with the downward thermal plume, the particle aspiration efficiency decreases by increasing the particle diameter from 5 to 100 micron. Results for particle depositions illustrated that most large microparticles were trapped inside the nasal cavity for both upward and downward thermal plumes around the mannequin. &nbsp;Furthermore, the regional particle deposition efficiencies for both thermal plume conditions were evaluated and discussed. &nbsp;</p>

Influence of Thermal Plume on Particle Inhalability of a Lying Mannequin in a Room

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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