by U ¼ Uff + Ufw, where Uff is fluid-fluid interaction potential and Ufw is fluid-

wall interaction potential expressed as

Uff ¼ 4εff

σff

rij



12

σff

rij



6

"

#

Ufw ¼ 4εfw

σfw

rij



12

σfw

rij



6

"

#

:

ð16:12Þ

Here, εff and σff are the parameters of LJ potential for fluid-fluid interactions.

Fluid-wall potential’s parameters are represented by εfw and σfw. The ratio εff/εfw

is an important parameter representing wettability of fluid. For example, for

water, larger values of εff/εfw represent a hydrophilic wall, whereas its smaller

value relates to a hydrophobic wall. Figure 16.16 shows a 3D plot of such a fluid-

0.0

0.2

0.4

0.6

0.8

1.0

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Velocity auto-coreelation function

t

Bulk

z=10

z=15

z=17

z=19

Fig. 16.14 Variation of normalized velocity autocorrelation function of fluid confined in rectan-

gular nanotube

Fig. 16.15 Variation of ratio of D(y, z) to the bulk value with z for fluids of different densities

292

K. Tankeshwar and S. Srivastava