Abstract
This study investigated the interaction of cough droplets with airflow in a realistic human airway. The ultimate aim was to assess the impact of pathological conditions on the retention and aspiration capacities of cough droplets in the airway. A Computational Fluid Dynamics (CFD) model, based on the Euler-Lagrangian framework was employed to predict the two-phase, droplet-laden transient cough flow in a realistic 3D human airway geometry reconstructed from patient CT scan dataset. The Discrete Phase Model (DPM) was used to track the motion of the droplets in the air flow. Two distinct cough profiles — a strong cough and a weak cough — acquired experimentally from human subjects, were used as input to simulate normal and disordered cough functions. The effects of cough strength and droplet size on droplet retention and aspiration in the airway were investigated. It was found that droplet retention was significantly higher for a weak cough compared to a strong cough. For a weak cough, the highest droplet retention percentage exceeded 60%, while for a strong cough, it was less than 20%. Larger sized droplets were more likely to be aspirated into the lungs, especially under weak cough conditions. In the case of weak cough, more than 5% of the 200 µm sized droplets were aspirated into the lungs, whereas for strong cough, aspiration was less than 2%.
