Fiber transport and deposition in human upper tracheobronchial airways

Using a multi-level asymmetric lung bifurcation model, transport and deposition of ellipsoidal fibers in the human upper airways were analyzed. The first three generations (G0–G3) of the tracheobronchial tree were included in the study. The focus of this research is airflow simulation and fiber motion prediction in the multi-level human airway bifurcation model. The laryngeal jet at the trachea entrance was modeled as an equivalent turbulence generator, and downstream in the lower level of the bronchi a laminar flow model was used. Lagrangian simulation of ellipsoidal fiber transport and deposition was performed where the effects of coupled hydrodynamic drag and torque, shear induced lift, gravitational sedimentation, inertial impaction, turbulence diffusion were included in the analysis. The study showed that the multi-level asymmetric lung bifurcation model was flexible, easy to use, and computationally highly efficient. The particle simulation results showed that the elongated fibers were aligned with the main flow direction most of the time, but occasionally they experienced impulsive rotation along their pathway. The rotational motion was dependent on the fiber geometry and the local flow patterns. Fiber deposition pattern and deposition rate in the human upper airways were evaluated. The simulation results were compared with the experimental data. The equivalent sphere model for fiber transport and deposition was also discussed.