Unsteady Particle Deposition in a Human Nasal Cavity

The deposition efficiency of unsteady inhalation is investigated in present study by using computational fluid dynamics techniques. Comparison with steady inhalation is also discussed. The inspiratory cycle of a realistic unsteady inhalation profile was applied at the outlet of nasopharynx, which has the maximum flow rate of 40.3L/min. Aerodynamic particle sizes of 5μm and 20μm were studied in order to reflect a low and high Stokes numbered particle, respectively. Three profiles of particle deposition efficiency in the nasal cavity versus time are presented. In general, the total deposition of 5μm was found much less than 20μm particle. Lower deposition was achieved for 5μm as inhalation accelerates. The first 0.2 second of the inspiratory cycle was found to be a crucial period as majority of particles deposited during the period. These particle sizes gave the highest deposition efficiency in the middle region of the nasal cavity. However, the distribution changed for large particle under steady inhalation. Comparing with its equivalent steady inhalation flow rate, the unsteady inhalation had lower deposition efficiency for both particle sizes.