Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Combined free-stream disturbance measurements and receptivity studies in
  hypersonic wind tunnels by means of a slender wedge probe and DNS   Combined free-stream disturbance measurements and receptivity studies in
hypersonic wind tunnels were conducted by means of a slender wedge probe and
direct numerical simulation. The study comprises comparative tunnel noise
measurements at Mach 3, 6 and 7.4 in two Ludwieg tube facilities and a shock
tunnel. Surface pressure fluctuations were measured over a wide range of
frequencies and test conditions including harsh test environments not
accessible to measurement techniques such as pitot probes and hot-wire
anemometry. Quantitative results of the tunnel noise are provided in frequency
ranges relevant for hypersonic boundary layer transition. In combination with
the experimental studies, direct numerical simulations of the leading-edge
receptivity to fast and slow acoustic waves were performed for the slender
wedge probe at conditions corresponding to the experimental free-stream
conditions. The receptivity to fast acoustic waves was found to be
characterized by an early amplification of the induced fast mode. For slow
acoustic waves an initial decay was found close to the leading edge. At all
Mach numbers, and for all considered frequencies, the leading-edge receptivity
to fast acoustic waves was found to be higher than the receptivity to slow
acoustic waves. Further, the effect of inclination angles of the acoustic wave
with respect to the flow direction was investigated. The combined numerical and
experimental approach in the present study confirmed the previous suggestion
that the slow acoustic wave is the dominant acoustic mode in noisy hypersonic
wind tunnels.

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The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
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The categories of this paper are: cs
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci