Computational fluid dynamics analysis of wall shear stresses between human and rat nasal cavities

Toxicology studies often use laboratory animals as surrogates for human subjects because of the relatively similar nasal anatomy that allows data extrapolation between species. An understanding of nasal airflow patterns, particularly wall shear stress can help better understand the causes of toxicant distribution and local dosimetry. A laminar, steady state flow was used to simulate light inhaled air. The WSS produced inside a human nasal cavity was compared with a rat nasal cavity. The results showed that averaged WSS was highest in the anterior nasal region, i.e. vestibule (rat - 755 mPa and human - 153 mPa). In the human model, the lower septal wall, and nasopharynx region also exhibited high WSS regions. Local high WSS regions on the nasal cavity wall were identified by plotting the WSS distribution as 3D contour maps on a normalised 2D domain. This visualisation technique displays peaks for locally high WSS values which were primarily caused by the airway geometry intruding into the airflow paths and causing high shear. Velocity vectors on the 2D domain also correlated high WSS with flow acceleration that was caused by a reduction in the cross-sectional area of a local region in the nasal passage.