Analysis of Flow Field Under Unsteady Breathing Conditions in a Realistic Human Nasal Cavity

Abstract The human nasal airway is a complex structure that provides the first line of defense to filter foreign particles before reaching the lungs. With the increased occurrence of nasal and nasopharyngeal cancers, understanding nasal airflow dynamics is crucial to assessing the potential airflow-related causes. Although human respiration is inherently unsteady, many earlier studies have been conducted for an effective steady breathing state. In this study, we analyzed unsteady respiration in a realistic human nasal cavity using the Ansys-Fluent software. A sinusoidal inhalation and exhalation at peak breathing of 10 1/min was simulated. It was found that the inhalation and exhalation breathing show different airflow dynamics. In particular, significant reversed flow conditions were observed at the entrance to the main nasal cavity from the pharynx during the exhalation phase. Both inhalation and exhalation exhibit significant acceleration and deceleration phases, with more prominent vortices forming during the deceleration phase of the inhalation period. Particular attention was given to the unsteady airflow condition in turbinate and olfactory regions. Our study showed that transient breathing in the nasal cavity and its impact on particle deposition needs further investigation.