Numerical Simulation of Airflow in the Human Nasal Cavity

Abstract

An anatomically correct finite element mesh of the right human nasal cavity was constructed from CAT scans of a healthy adult nose. The steady-state Navier-Stokes and continuity equations were solved numerically to determine the laminar airflow patterns in the nasal cavity at quiet breathing flow rates. In the main nasal passages, the highest inspiratory air speed occurred along the nasal floor (below the inferior turbinate), and a second lower peak occurred in the middle of the airway (between the inferior and middle turbinates and the septum). Nearly 30 percent of the inspired volumetric flow passed below the inferior turbinate and about 10 percent passed through the olfactory airway. Secondary flows were induced by curvature and rapid changes in cross-sectional area of the airways, but the secondary velocities were small in comparison with the axial velocity through most of the main nasal passages. The flow patterns changed very little as total half-nasal flow rate varied between resting breathing rates of 125 m/s and 200 ml/s. During expiration, the peaks in velocity were smaller than inspiration, and the flow was more uniform in the turbinate region. Inspiratory streamline patterns in the model were determined by introducing neutrally buoyant point particles at various locations on the external naris plane, and tracking their path based on the computed flow field. Only the stream from the ventral tip of the naris reached the olfactory airway. The numerically computed velocity field was compared with the experimentally measured velocity field in a large scale (20x) physical model, which was built by scaling up from the same CAT scans. The numerical results showed good agreement with the experimental measurements at different locations in the airways, and confirmed that at resting breathing flow rates, airflow through the nasal cavity is laminar.

From CT Scans to CFD Modelling – Fluid and Heat Transfer in a Realistic Human Nasal Cavity

“…Despite the small difference in area coverage, region D in the left cavity exhibits a small constricting section which causes a higher resistance in the flow and hence the smaller proportion of airflow through sections C, D and E. The flow in the left cavity stays close to the wall and its distribution is mainly in the middle sections and more dominant in the lower sections, while a small percentage (11.6%) is found in the upper section. This pattern was also observed in the work by Hahn, Scherer and Mozell (1993) and in the model of Keyhani, Scherer and Mozell (1995). In the right cavity the flow is concentrated within the middle sections.…”

“…It was found that the projection of the inferior turbinates was the only significant parameter and that a greater projection of the inferior turbinate bone laminated the flow by simply decreasing the cross-sectional area of the passageway while larger passageways, with a greater hydraulic diameter, would experience more turbulent flow. The increase in computational power has allowed many numerical simulations, including the pioneering work of Keyhani, Scherer and Mozell (1995) among others. Without considering humidity and water exchange, Lindemann et al (2004) numerically simulated the temperature distribution during inspiration in an anatomically realistic nasal cavity.…”

How much does nasal cavity morphology matter? Patterns and rates of olfactory airflow in phyllostomid bats

“…Though the velocity of air moving through the nasal passages is in fact time-varying, we assumed steady-state flow to match most previous work on the subject (e.g. [4][5][6][7][8][9][10]) and because good agreement exists between patterns of flow between steady and unsteady regimes [33].…”

“…dogs [3,5]; rats [6][7][8]), and those with a small olfactory region and poorly developed sense of smell on the other (e.g. humans [9,10]). To date, no study has attempted to use a group of closely related species to more precisely link differences in their apparent reliance on olfaction with differences in airway morphology and patterns of airflow.…”

Airflow and Deposition of Nano-Particles in a Human Nasal Cavity

“…Keyhani et al (1995) simulated the steady flow in the nose by the finite element method using FIDAP TM commercial software. Their 3D computational model for one of the nasal cavities from the nostril to the beginning of nasopharynx was constructed from the CAT scan sections of a human subject.…”