A study of radiating argon flows at high opacities
Date
1972
Authors
Logan, Peter Frederick
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Abstract
The aim of this project was to investigate the effect of
radiation loss on the various flows associated with a free piston
reflected shock tunnel assembly.
Experiments have been performed using argon as a test gas
because the radiation loss with argon is quite considerable under the
thermodynamic conditions experienced in this study. The nature of the
experiments was mainly spectroscopic.
This investigation has shown that?using a careful analysis^the
behaviour of a high performance shock tunnel?which experiences substantial
radiation losses.can be explained during the first one hundred
microseconds of test section flow. An appropriate model is developed to
account for the emitted and absorbed radiation from the test gas, both
behind the incident shock and the reflected shock, during this period.
At later times a quantitative description could not be obtained since
interaction between the reflected shock and the boundary layer introduced
contamination into the reflected shock region. From the theoretical
analysis of the radiative behaviour of the gas flows associated with free
piston reflected shock tunnels, a limiting value for their operation can
be obtained.
A further study proceeded from this investigation. The gas in
the stationary slug at the end of the shock tube is optically opaque
towards all visible and near visible radiation. Whereas the gas at the
exit of the nozzle is optically thin. Hence the radiation field
observed looking up the centre of the nozzle is similar to that of a
stellar atmosphere?and a Fraunhofer type spectrum was observed. A
preliminary investigation of both the mechanism by which the spectral
lines are formed#and their application^is reported.
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