Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Different transport regimes in a spatially-extended recirculating
  background   Passive scalar transport in a spatially-extended background of roll
convection is considered in the time-periodic regime. The latter arises due to
the even oscillatory instability of the cell lateral boundary, here accounted
for by sinusoidal oscillations of frequency $\omega$. By varying the latter
parameter, the strength of anticorrelated regions of the velocity field can be
controled and the conditions under which either an enhancement or a reduction
of transport takes place can be created. Such two ubiquitous regimes are
triggered by a small-scale(random) velocity field superimposed to the
recirculating background. The crucial point is played by the dependence of
Lagrangian trajectories on the statistical properties of the small-scale
velocity field, e.g. its correlation time or its energy.

36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th