Numerical study of single-cough generated droplets inhalation and deposition in an airway under realistic cyclic breathing in a quiescent air condition

This study analyzed aspiration and deposition of generated droplets from a single-cough event of an infected person in the airway of a receptor person. For this purpose, two humanoid mannequins in the face-to-face orientation at a distance of 0.5 m from each other inside the quiescent air condition were considered. The healthy receptor person's airway extended from the nostril to the end of 4th lung generation was included in the simulation. The realistic cyclic breathing of the receptor mannequin was also simulated. It was assumed that the infected person's coughing event occurred at the exhalation of the receptor person's breathing. The Ansys-Fluent software was used for all simulations, and the SST k-omega turbulence model was employed to simulate the cough, the inhalation, and the surrounding airflow fields. The cough droplet motions were simulated using the Lagrangian particle trajectory analysis approach. User-defined functions for an improved DRW model were developed and implemented into the Ansys-Fluent software. Airflow field simulation results showed that the coughing jet flow led to the formation of vortices near the coughing mannequin. Vortices form and evolve in time during the transient cough jet flow. Also, the coughing event generates a cloud of droplets that spreads in time. Simulation of droplets' motions showed that inhalation and deposition of droplets inside the receptor airway in the deceleration phase of inhalation were more than in the acceleration phase. In addition, the aspiration of droplets in the first breathing cycle after the cough was more than in the second cycle. Furthermore, results showed that maximum regional deposition occurred in the vestibule, and the penetration of droplets in the left lower lobe and right lower lobe was more than in other lung lobes. Finally, the deposition and penetration of droplets in the right lung were more than in the left lung.