Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Roughness gradient induced spontaneous motion of droplets on hydrophobic
  surfaces: A lattice Boltzmann study   The effect of a step wise change in the pillar density on the dynamics of
droplets is investigated via three-dimensional lattice Boltzmann simulations.
For the same pillar density gradient but different pillar arrangements, both
motion over the gradient zone as well as complete arrest are observed. In the
moving case, the droplet velocity scales approximately linearly with the
texture gradient. A simple model is provided reproducing the observed linear
behavior. The model also predicts a linear dependence of droplet velocity on
surface tension. This prediction is clearly confirmed via our computer
simulations for a wide range of surface tensions.

3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn