Advanced Topics and Future Trends - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 328

Fig. 9.12 Distribution of the initial locations of deposited particles in the plane parallel to the wall
a d = 0 . 01 μ m, b 0.15 μ m, c 25 μ m, d 50 μ m. (From Zhang and Ahmadi, 2000)

Here, L 1 3 . 08 / ( Sd + ), g + = ( v/u ∗ 3 ) g , and k r = is the surface roughness (zero for

smooth surfaces).
To shed light on the interaction of particles with near wall coherent eddies, Zhang
and Ahmadi (2000) performed a series of simulations releasing the particles of dif-
ferent sizes near the wall and tracing their trajectory. For 0.01, 15, 25, and 50 m

particles that deposit on the wall, their locations are recorded and plotted in Fig. 9.12 .
Here the depositions within 100 wall units of time are considered. Figure 9.12 a shows
that the locations of deposited 0.01

μ

m particles are randomly distributed. This is
because, for nanometre particles, the Brownian diffusion strongly affects the deposi-
tion process so that the effect of turbulence coherent eddies is smeared. Figure 9.12 b
shows that the locations of deposited 15

μ

m particles in the plane parallel to the
wall are concentrated in certain bands, which are about 100 wall units apart. Similar

μ