Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Levitation of heavy particles against gravity in asymptotically downward
  flows   In the fluid transport of particles, it is generally expected that heavy
particles carried by a laminar fluid flow moving downward will also move
downward. We establish a theory to show, however, that particles can be
dynamically levitated and lifted by interacting vortices in such flows, thereby
moving against gravity and the asymptotic direction of the flow, even when they
are orders of magnitude denser than the fluid. The particle levitation is
rigorously demonstrated for potential flows and supported by simulations for
viscous flows. We suggest that this counterintuitive effect has potential
implications for the air-transport of water droplets and the lifting of
sediments in water.

25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat