49 research outputs found
Spreading of Fluids on Solids Under Pressure: Effect of Slip
Spreading of different types of fluid on substrates under an impressed force
is an interesting problem. Here we study spreading of four fluids, having
different hydrophilicity and viscosity on two substrates - glass and perspex,
under an external force. The area of contact of fluid and solid is
video-photographed and its increase with time is measured. The results for
different external forces can be scaled onto a common curve. We try to explain
the nature of this curve on the basis of existing theoretical treatment where
either the no-slip condition is used or slip between fluid and substrate is
introduced. We find that of the eight cases under study, in five cases
quantitative agreement is obtained using a slip coefficient.Comment: 6 figure
Euler Number and Percolation Threshold on a Square Lattice with Diagonal Connection Probability and Revisiting the Island-Mainland Transition
We report some novel properties of a square lattice filled with white sites,
randomly occupied by black sites (with probability ). We consider
connections up to second nearest neighbours, according to the following rule.
Edge-sharing sites, i.e. nearest neighbours of similar type are always
considered to belong to the same cluster. A pair of black corner-sharing sites,
i.e. second nearest neighbours may form a 'cross-connection' with a pair of
white corner-sharing sites. In this case assigning connected status to both
pairs simultaneously, makes the system quasi-three dimensional, with
intertwined black and white clusters. The two-dimensional character of the
system is preserved by considering the black diagonal pair to be connected with
a probability , in which case the crossing white pair of sites are deemed
disjoint. If the black pair is disjoint, the white pair is considered
connected. In this scenario we investigate (i) the variation of the Euler
number versus graph for varying , (ii)
variation of the site percolation threshold with and (iii) size
distribution of the black clusters for varying , when . Here is
the number of black clusters and is the number of white clusters, at a
certain probability . We also discuss the earlier proposed 'Island-Mainland'
transition (Khatun, T., Dutta, T. & Tarafdar, S. Eur. Phys. J. B (2017) 90:
213) and show mathematically that the proposed transition is not, in fact, a
critical phase transition and does not survive finite size scaling. It is also
explained mathematically why clusters of size 1 are always the most numerous