Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Filamentary Surface Plasma Discharge Flow Length and Time Scales   Nanosecond Surface Dielectric Barrier Discharge (ns-SDBDs) are a class of
plasma actuators that utilize a high-voltage pulse of nanosecond duration
between two surface-mounted electrodes to create an electrical breakdown of
air, along with rapid heating. These actuators usually produce multiple
filaments when operated at high pulse frequencies, and the rapid heating leads
to the formation of shock waves and complex flow fields. In this work we
replicate a single filament of the ns-SDBDs and characterize the induced flow
using velocity measurements from particle image velocimetry and density
measurements from background-oriented schlieren. The discharge is produced by a
high voltage electrical pulse between two copper electrodes on an acrylic base.
A hot gas kernel characterizes the flow field formed close to the electrodes
that expands and cools over time and a vortex ring that propagates away from
the surface while entraining cold ambient fluid. The gas density deficit inside
the kernel displays a power-law decay over time. Based on the observations, we
develop a simplified theoretical model based on vortex-driven cooling and
perform a scaling analysis to obtain the induced flow length and time scales.
The results show that the cooling process's time scales correspond to a
circulation-based time scale of the vortex ring, and the length scale of the
kernel corresponds to the vortex ring radius. These findings can guide the
choice of optimal filament spacing and pulse frequencies in the design,
deployment, and operation of nanosecond surface dielectric barrier discharges
(ns-SDBDs) for flow control.

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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ph
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The categories of this paper are: math
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph