Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Forward and backward in time dispersion of fluid and inertial particles
  in isotropic turbulence   In this paper we investigate both theoretically and numerically the forward
in time (FIT) and backward in time (BIT) dispersion of fluid and inertial
particle pairs in isotropic turbulence. Fluid particles are known to separate
faster BIT than FIT in three-dimensional turbulence, and we find that inertial
particles do the same. However, we find that the irreversibility in the
inertial particle dispersion is in general much stronger than that for fluid
particles. For example, the ratio of the BIT to FIT mean-square separation can
be up to an order of magnitude larger for inertial particles than for the fluid
particles. We also find that for both the inertial and fluid particles the
irreversibility becomes stronger as the scale of their separation decreases.
Regarding the physical mechanism for the irreversibility, we argue that whereas
the irreversibility of fluid particle-pair dispersion can be understood in
terms of a directional bias arising from the energy transfer process in
turbulence, inertial particles experience an additional source of
irreversibility arising from the non-local contribution to their velocity
dynamics, a contribution which vanishes in the limit ${St\to0}$, where $St$ is
the particle Stokes number. For each given initial (final, in the backward in
time case) separation $\bm{r}^0$ there is an optimum value of $St$ for which
the dispersion irreversibility is strongest, as such particles are optimally
affected by both sources of irreversibility. We derive analytical expressions
for the BIT, mean-square separation of inertial particles and compare the
predictions with...

33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn