Case Studies in the Human Respiratory System - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 265

Fig. 8.23 Typical CFD
results demonstrating. a flow
field through streamlines and
velocity contours and b wood
dust particles passing through
a breathing plane, for a wood
turning work station

Fig. 8.24 Cumulative
deposition efficiency and
regional deposition for 16 and
30 μm pollen particles

40

16micron
30micron

30

20

10

0

123456 78 9 0
Region

between Region 2-3 is the nasal valve region—the smallest cross-sectional area that
causes acceleration of the fluid flow. Posterior to the nasal valve, the particles deposit
in the upper region of the nasal cavity due to the momentum of the particles exiting
the nasal valve. The deposition of particles in Region 6 may also be a cause for
irritation and inflammation to the mucosal walls. Further along the nasal cavity, the
deposition pattern (Fig. 8.25 ) shows particles depositing at the nasopharynx where
the flow changes direction at 90 ◦ (i.e. inertial impaction).
A comparison with a normal spherical particle having the same aerodynamic
diameter can be made through the inertial parameter. Table 8.7 shows that higher
deposition occurs for spherical particles in comparison with near-spherical particles.