Development of Improved Computer Simulation Models of Fibre Transport and Deposition in Alveolar Ducts

We introduce a model of fibre transport and deposition in alveolar ducts. The steady incompressible Navier–Stokes equations are solved to obtain velocity profiles in two-dimensional regions that represent bifurcating alveolar ducts with and without alveoli. The drag coefficients of a fibre are also calculated. Using these data, we simulate the deterministic motion of a fibre through the duct until it makes contact with a wall surface or exits. We found that deposition of fibres of diameter 1 μm with an aspect ratio of 10 is dominated by sedimentation. The presence of alveoli leads to air flow patterns quite different from those in ducts without alveoli. They have no effect on the total deposition of large fibres, but they modulate the pattern of deposition, leading to large variations of dose within a duct. We also found that deposition is highly sensitive to the duct's angle of orientation with gravity. This suggests difficulties for whole lung models of deposition which use an average angle of orientation for all airways.