LAUSR

It is critical to understand the airflow structures in the respiratory system toward increasing the drug delivery efficiency via inhalation. A whole-lung airway model is created by connecting a three-dimensional cast-based mouth–throat model and a one-dimensional conduit describing the other lung airways according to the literature. Constant displacement of the bottom surface in the geometrical model is used to simulate the respiratory process. Large eddy simulation with the dynamic structure sub-grid scale model is used to model the turbulent flow via a commercial computational fluid dynamics software, ConvergeTM. The innovative findings are as follows: (1) shear layer as well as vortical flow is observed in the lower airway at the inspiration phase; (2) the main airflow structures in the upper airway of this model are close to the case using the mouth–throat model; (3) the airflow structures, in particular the reversed laryngeal jet, are highly unsteady during the expiration phase. It is shown that this whole-lung airway model is suitable to analyze the airflow field in the upper airway but not in the lower airway, although it has been used a lot by a few researchers. More investigations should be carried out to study the dynamics of airflow structures during the expiration phase toward understanding airflow properties of human respiratory process.