normalized velocity autocorrelation function (VACF) of fluid confined to rectan-
gular nanotube as a function of z has been depicted in Fig. 16.14, whereas ratio of
D(y, z) to the bulk value as a function of z (walls of tube are at z ¼ 20) for y ¼ 20
has been displayed in Fig. 16.15. The model envisages that the self-diffusion near
the walls (of the order of few atomic layers) of the nanotube falls off significantly.
The effect of such confinement on dynamic motion could lead to solidification of
liquid close to the walls, and such a transition is effectively dynamical in nature. It
is also discovered that effect of confinement on dynamics also determined by the
radii of the particles. Subsequently, width of the tube cannot be treated as absolute
and must always be quantified in terms of radius of particles contained in it. It is
also observed that effect of confinement is more pronounced on denser fluids as
compared to that on dilute fluids.
3. Wall-Fluid Interaction: The self-diffusion of fluid is calculated by incorporating
the fluid-wall interaction at the atomic level (Devi et al. 2015). The fluid-fluid and
fluid-wall interactions have been assumed to be LJ 12-6 potential and are given
Fig. 16.12 Particle in a
compressed cell
1
0.8
0.6
0.4
0.2
0
20
18
18
16
16
14
14
12
12
10
10
8
8
6
6
4
4
2
2
0
0
Z
Y
D(y,z)/
D(0)
Fig. 16.13 3D Plot of diffusion
16
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