Velocity profiles measured for airflow through a large-scale model of the human nasal cavity

Abstract

An anatomically accurate, x20 enlarged scale model of a healthy right human adult nasal cavity was constructed from computerized axial tomography scans for the study of nasal airflow patterns. Detailed velocity profiles for inspiratory and expiratory flow through the model and turbulence intensity were measured with a hot-film anemometer probe with 1 mm spatial resolution. Steady flow rates equivalent to 1,100, 560, and 180 ml/s through one side of the real human nose were studied. Airflows were determined to be moderately turbulent, but changes in the velocity profiles between the highest and lowest flow rates suggest that for normal breathing laminar flow may be present in much of the nasal cavity. The velocity measurements closest to the model wall were estimated to be inside the laminar sublayer, such that the slopes of the velocity profiles are reasonably good estimates of the velocity gradients at the walls. The overall longitudinal pressure drop inside the nasal cavity for the three inspiratory flow rates was estimated from the average total shear stress measured at the central nasal wall and showed good agreement with literature values measured in human subjects.

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 has, however, been shown experimentally that the oscillatory effects are not present until α = > 4 (Isabey and Chang, 1981). Additionally other studies have also concluded that under most conditions especially low flow rates, the nasal airflow can be considered quasi-steady (Chang, 1989;Hahn, Scherer and Mozell, 1993;Sullivan and Chang, 1991).…”

“…A flow rate of 15 L/min was used to simulate light adult breathing. At this flow rate, the flow regime has been determined to be laminar (Hahn, Scherer and Mozell, 1993;Swift and Proctor, 1977). A steady flow rather than a cyclic unsteady flow was used in this case to allow the results to emphasize the airflow dynamics and patterns independent of cyclic conditions.…”

Rapid and Precise Control of Sniffing During Olfactory Discrimination in Rats

“…For rats the frequency of sniffing is typically in the "theta" frequency range (4 -12 Hz) during olfactory discrimination (Rajan et al 2006;Uchida and Mainen 2003;Youngentob et al 1987) or exploration (Welker 1964), but how accurately sniffing frequency can be regulated and whether olfactory performance depends on the exact sniffing frequency is not known. Respiratory airflow and several other character-istics of sniffing covary with its frequency (Walker et al 1997;Youngentob et al 1987), so high frequencies could enhance olfactory transduction (Hahn et al 1993;Kimbell et al 1997). Alternatively, particular sniffing frequencies within the theta (4-to 12-Hz) range may be favorable for the coordination of olfactory processing with other brain regions (Kay 2005;Kepecs et al 2006;Komisaruk 1977).…”

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

“…They also reported the presence of a relatively large vortex and a smaller one in the upper and the floor of the region posterior to the nasal valve. Hahn et al (1993) created a 20 times magnified model and measured the flow velocity at several points in the five coronal 465 planes throughout the model with a hot film anemometer. They reported that the flow was laminar up to a breathing rate of 24 L/min.…”