Case Studies in the Human Respiratory System - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 242

to curve downwards, the flow streamlines reflect this by pointing in the negative
y -direction.

8.2.6 Flow Features in the Nasal Valve

Two cross-sectional areas located just proximal to the anterior nasal valve at x =

2 . 6cmand x 3 . 2 cm were chosen to highlight the rapid changes in the flow field

since the anterior nasal valve was located at x

=

2 cm posterior to the anterior nares.
The naming convention used in this paper for the left and right cavity takes on the side
that the cavity sits anatomically. The cross-section shown in Fig. 8.9 is from a frontal
perspective (positive flow into the paper) and therefore the right cavity is depicted on
the left side. Similar to Fig. 8.8 . contour plots of the axial velocity ( x -component of
velocity) combined with streamlines of secondary flow ( y-z component of velocity)
is shown here.

=

Fig. 8.9 Velocity field in the
coronal cross-section located
at 2.60 cm from the anterior
tip of the nose. a At flow rate
of 7.5 L/min and b At flow
rate of 15 L/min

Right Left

a

7.5L/min

Right Left

b 15L/min

By applying the directional streamlines, secondary flow features such as vortices
can be visualised. The air enters the vestibule region with a vertical direction. And
as the distance increases from the anterior tip of the nostrils, the nasal geometry
becomes narrow as the airstream turns posterior, approximately 90 ◦ towards the
nasopharynx. This transition coupled with the narrowing geometry forces the flow to
emerge from the outer walls from the septum and be directed inwards. The presence