Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Contactless generation and trapping of hydrodynamic knots in sessile
  droplets by acoustic screw dislocations   Hydrodynamics knots are not only promising elementary structures to study
mass and momentum transfer in turbulent flows, but also potent analogs for
other topological problems arising in particle physics. However, experimental
studies of knots are highly challenging due to the limited control over knot
generation and difficult observation of the resulting fast-paced multiscale
flow evolution. In this paper, we propose using acoustic streaming to tie
hydrodynamic knots in fluids. The method is contactless, almost instantaneous
and is relatively insensitive to viscosity. Importantly, it allows starting
from quite arbitrary three dimensional flow structures without relying on
external boundary conditions. We demonstrate our approach by using an acoustic
screw dislocation to tie a knot in a sessile droplet. We observe an inversion
of the knot chirality (measured by the hydrodynamic helicity) as the
topological charge of the screw dislocation is increased. Combined with recent
progress in acoustic field synthesis, this work opens a window to study more
complex hydrodynamic knot topologies at a broader range of space and
timescales.

7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys