A CFPD-FSI analysis of the impact of nasal hairs on airflow patterns, nasal resistance, and particle filtration in a realistic human nasal airway.

Human nasal hair has a potential capability to maintain respiratory health, yet its functional significance is frequently underappreciated due to cosmetic preferences. Despite its physiological relevance, the mechanical influence of nasal hair on airflow dynamics and particle deposition remains inadequately understood. This study used computational fluid-particle dynamics and fluid-structure interaction (CFPD-FSI) simulations to analyze three distinct nasal hair configurations in a realistic human nasal airway model under steady laminar flow conditions (5 and 10 L/min per cavity). The Discrete Phase Model (DPM) was utilized to predict the transport and deposition of microparticles in the nasal cavity with and without nasal hairs. The one-way coupled CFD-FSI study showed that the investigated airflow rates lead to a negligible deformation in hairs (in the worst-case scenario, 7.8 μm at the hair tip), which implies that the rigid hair assumption can be confidently used for the nasal hairs in the laminar regime. The findings also revealed that the presence of nasal hair can increase nasal resistance by approximately 20-80% while enhancing micro-particle filtration efficiency by 12-38%, depending on the morphological configuration. Furthermore, the results demonstrated that nasal hair alters local airflow patterns in the anterior part of the upper airways, specifically by enhancing swirling flows in the nasal valve region, thereby increasing deposition fraction in this zone. These findings provide quantitative evidence of the physiological role of nasal hair as a protective filtration mechanism and its simultaneous unfavorable impact on nasal resistance and intranasal drug delivery.