Two- and three-dimensional simulations of aerosol transport and deposition in alveolar zone of human lung

We simulate two- and three-dimensional (2D and 3D) aerosol transport for different particle diameters within alveolated ducts. In agreement with previous studies (W. J. Federspiel and J. J. Fredberg. J. Appl. Physiol. 64: 2614-2621, 1988; A. Tsuda, J. P. Butler, and J. J. Fredberg. J. Appl. Physiol. 76: 2497-2509, 1994), the 2D-computed velocity field shows that the flow inside the alveoli is negligible compared with that in the central channel of the ducts and that a recirculation zone is set up in each alveolus. The calculated particle trajectories indicate that in the 2D and 3D simulations the particles do not deposit uniformly on the alveolar walls. For <0.5-mu m-diameter particles, simulations show that particles are mainly located near the entrance of the alveoli. This suggests that local and mean aerosol concentrations may be substantially different. For large particles we show that the gravity field significantly affects deposition. Aerosol dispersion is also computed, and the simulations are compared with the classical one-dimensional (1D) approach with use of the trumpet model, with additional terms for deposition. The 3D model simulates total deposition that is intermediate between 1D and 2D models. The differences between 2D and 3D data are attributed to the inclusion of azimuthal alveolar walls in the 3D duct and the change from 2D- to 3D-particle motions. Finally, our work suggests that the 1D model may introduce large errors in the location of deposited particles.