In this study, unsteady flow field and fibrous particle deposition in a realistic model of human upper airway system including vestibule to the end of trachea were investigated using the CFD technique. The airway passage model was constructed from the CT image of a 24 year old healthy woman.

Unsteady airflow patterns during a full breathing cycle were simulated by solving the Navier-Stokes and continuity equations. For ellipsoidal fiber trajectory analysis under cyclic breathing condition, several user defined functions (UDFs) were coupled to the ANSYS-Fluent discrete phase model (DPM). The presented formulation accounted for solving the coupled translational and rotational equations of motion of ellipsoidal fibers.

Total and regional depositions for a range of fiber sizes were evaluated. The transient particle deposition fraction was compared with those obtained from the equivalent steady flow condition. The presented results showed that the steady simulation can predict the total fibrous particle deposition during cyclic breathing with reasonable accuracy but cannot properly predict the regional deposition of particles.

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