INERTIAL AND GRAVITATIONAL DEPOSITION OF PARTICLES IN A SQUARE CROSS-SECTION BIFURCATING AIRWAY

Deposition of spherical particles in an airway bifurcation is studied numerically. Airway dimensions are based on the third airway generation of the Weibel symmetric lung model (1963). A square cross-sectional airway area is assumed, with parent and daughter tubes having different diameters. The flow field is solved by a finite element method for Reynolds numbers of 100 and 1000 with uniform and parabolic parent inlet velocities. The How field is then used to calculate particle deposition in this geometry. Deposition by the mechanisms of impaction and sedimentation are incorporated. The results show that for particles larger than 10 mum, sedimentation losses are weakly dependent on the flow Reynolds number and the inlet condition, whereas impaction losses depend strongly on Reynolds number and inlet condition. Also, the calculated results gave good agreement with the predictive model of Pich (1972) for sedimentation losses in flows through parallel plates. For losses by impaction, the calculated results also agreed with the results or Kim and Iglesias (1989) and differed from the theoretical model of Cai and Yu (1988). Further differences were observed when the current findings were compared with the data of Pui et al. (1991) for particle loss in a 90-degrees bent, suggesting that geometric features play an important role in deposition of particles.