Cyclic micron-size particle inhalation and deposition in a triple bifurcation lung airway model

Laminar oscillatory inhalation flow as well as micron-particle transport and wall deposition in a representative triple bifurcation airway model have been simulated using a commercial finite-volume code with user-enhanced programs. The computer model has been validated with experimental particle deposition data and deposition patterns for double bifurcations. The transient air flow, particle transport, and wall deposition patterns were analyzed and summarized in terms of particle deposition efficiencies (DEs) and surface density maps. Particle deposition may increase under cyclic flow conditions, i.e., DE-values are typically larger for cyclic flow than for steady flow at the mean flow rate of a given inhalation pulse. The maximal relative difference between these two DE-values may be as high as 50% for 0.02 Stmean 0.12 during normal inspiration (Qin=30 l/min). However, matching inlet Reynolds and Stokes numbers are proposed, which generate under quasi-steady flow conditions very similar DE-values and deposition patterns as in equivalent pulsatile flow. The relative differences between DE-values for cyclic and matching steady cases are less than 5%. The quantitative results of this work are of interest to researchers either conducting health risk assessment studies for inhaled particulate pollutants or analyzing drug aerosol deposition at desired lung target sites.