Session: 7.4.2 - Fluid-Solid Flows II

Paper Number: 158072

158072 - Influence of Thermal Plume on Cough-Generated Droplet Aspiration and Deposition in the Airway Under Unsteady Breathing 

Abstract: 

This study deals with numerical simulations of single-cough event airflow and cough-generated droplet inhalation and deposition in the airway under unsteady breathing conditions. A (healthy) receptor mannequin with an attached airway from the nostril inlet to the end of the 4th lung generation was placed face-to-face with an (infected) cougher mannequin at a distance of 0.5 m. For the airflow in the room, two cases with and without thermal plumes around the mannequins were considered. An unsteady cyclic breathing pattern with a duration of 5.4 s, equivalent to a steady breathing flow rate of 20 lit/min, was assumed for the receptor mannequin respiration. For numerical simulations, 4 receptor breathing cycles corresponding to 21.6 s were simulated. The coughing event with 0.42 s duration starts at 10.37 s after receptor mannequin breathing, corresponding to 4.97 s after the start of the second breathing cycle. The low Reynolds SST k- turbulence model was used for the simulation of the airflow field using Ansys-Fluent software. The motion of cough droplets was simulated with the Lagrangian approach. A user-defined function (UDF) was employed for the stochastic modeling of turbulence fluctuations coupled into the Ansys-Fluent discrete phase model. For particle tracking, a total of 106,470 spherical droplets with 2, 5, 10, 15, and 20 µm diameter and unit density were released during 0.42 s of cough event. Results of the airflow pattern in the room and droplets’ dispersion, aspiration, and deposition in the receptor’s mannequin airway were presented and discussed.

The simulation results showed that the thermal plume influenced the airflow around the mannequins. In addition, the total aspiration fraction of droplets with the thermal plume is much more than the case without the thermal plume. The total deposition of small droplets inside the receptor’s mannequin airway is higher by considering the influence of the thermal plume. Deposition of droplets in the vestibule, main airway and branches is higher than the other parts of the airway. However, the regional deposition of droplets in the vestibule is similar with and without the thermal plume.

Presenting Author: Goodarz Ahmadi Clarkson Univ

Presenting Author Biography: Professor Goodarz Ahmadi is a Distinguished Professor of Mechanical Engineering at Clarkson University.