Aerosol transport and deposition in sequentially bifurcating airways

Deposition patterns and efficiencies of a dilute suspension of inhaled part icles in three-dimensional double bifurcating airway models for both in-pla ne and 90 deg out-of-plane configurations have been numerically simulated a ssuming steady, laminar, constant-property air flow with symmetry about the first bifurcation. Particle diameters of 3, 5, and 7 mum were used in the simulation, while the inlet Stokes and Reynolds numbers varied from 0.037 t o 0.23 and 500 to 2000 respectively. Comparisons between these results and experimental data based on the same geometric configuration showed good agr eement. The overall trend of the particle deposition efficiency, i.e., an e xponential increase with Stokes number, was somewhat similar for all bifurc ations. However, the deposition efficiency of the first bifurcation was alw ays larger than that of the second bifurcation, while in general the partic le efficiency of the out-of-plane configuration was larger that that of the in-plane configuration. The local deposition patterns consistently showed that the majority of the deposition occurred in the carinal region. The dis tribution pattern in the first bifurcation for both configurations were sym metric about the carina, which was a direct result of the uniaxial flow at the inlet. The deposition patterns about the second carina showed increased asymmetry due to highly nonuniform flow generated by the first bifurcation and were extremely sensitive to bifurcation orientation. Based on the depo sition variations between bifurcation levels and orientations, the use of s ingle bifurcation models was determined to be inadequate to resolve the com plex fluid-particle interactions that occur in multigenerational airways. [ S0148-0731(00)01102-X].