Simulation of airflow fields and microparticle deposition in realistic human lung airway models. Part I: Airflow patterns

In Part I, transient and steady laminar airflow fields were simulated with an in-house finite volume code for realistic upper airway models subject to different inlet conditions and geometric features. Axial velocities and secondary flows were compared at key time levels during the acceleration/deceleration phase of inhaled air and for steady-state inhalation. The main results can be summarized as follows. Considering two acceleration and deceleration time levels during transient inhalation as well as steady-state inhalation generating the same inlet Reynolds number, Rein-mean=1201, the airflow patterns are quite similar. However, stronger axial and secondary velocities occur at all upper branch locations during flow deceleration because of the dynamic lingering effect. In general, the axial velocity profiles at steady state are very close to those at the point of deceleration. Variations in upper airway geometry, e.g., in-plane vs. out-of-plane configurations, have a significant effect on the airflow fields, although the primary airflow structures are similar in both idealized and more realistic airway configurations. The type of velocity inlet condition and existence of cartilaginous rings also influence the flow field; however, their impact is less important than changes in spatial angles.