Confinement and Interaction Effects on the Diffusion of Passive Particles - Selected Topics of Computational and Experimental Fluid Mechanics - page 375

Fig. 4 (Color online) Particles inside a triangular cavity ( ˁ ∗ = 0 . 5) interacting bymeans of different
potentials. a Particles interacting by means of a SLJ potential; b Particles interacting by means of
a HLJ potential. Note that HLJ particles produce more free space, see ( b ), compared with particles
interacting by means of a SLJ, see ( a )

also shows an interesting effect due to an interplay among confinement and particle
interaction. We notice that order appears for particles interacting with a SLJ and for
all the three cavity shapes. This order reduces the MSD compared with the MSD of
systems at the same density but subject to CLJ or HLJ (see Fig. 3 , third row, second
column). Figure 3 also shows that order appears as the strength of the interaction
potential grows, however this order slowly disappears as the strength of U ij is still
growing (that is, if we make 2 n

= ,

40 and so on). Note for example that the
HLJ potential at this density does not show order, hence its MSD increases again.
The appearance of order is visually shown in Fig. 5 where one can see that order has
emerged in the left triangular cavity interacting by means of a SLJ (see Fig. 5 a). In
contrast, the right triangular cavity does not show order thus allowing the particles
to have more freedom and hence a higher MSD.
Figure 6 shows once again three representative density scenarios (0

36

. 1, 0 . 5 and

0 . 75). This time, each column shows the mean-square displacement for the same

(Color online) Particles inside a triangular cavity ( ˁ ∗ Fig. 5 75) interacting by means of

different potentials. a Particles interacting by means of a SLJ potential; b Particles interacting by
means of a HLJ potential. Order has emerged in the left triangular cavity interacting by means of a
SLJ, see ( a )

= 0 .