Author:
NAUGHTON JONATHAN W.,CATTAFESTA III LOUIS N.,SETTLES GARY S.
Abstract
Compressible jets with various amounts of swirl and
compressibility are investigated experimentally. The mixing-layer
growth rate is obtained from time-averaged images of the mixing layer
using the planar laser scattering (PLS) technique, and the swirl is
quantified with laser Doppler velocimetry and intrusive probes. The
results conclusively demonstrate that the addition of swirl to the
jet increases entrainment by up to 60% compared to a corresponding
non-swirling case. Instantaneous PLS images reveal modified turbulent
structure in the mixing layer of the swirling-jet cases. In
particular, analysis of these images indicates that both the spatial
extent and amplitude of the largest turbulent fluctuations are
increased when swirl is added. Based upon these results, a parameter
β that correlates the observed growth-rate enhancement is
proposed. This parameter is derived assuming that the streamwise
vorticity, generated in the mixing layer by the addition of small
amounts of swirl, causes additional turbulent mixing that increases
the growth rate. When the available growth-rate data for swirling
jets are plotted against this parameter, they collapse to a single
curve with increased enhancement for higher values of β. This
result implies that the degree of enhancement actually increases with
compressibility, although the dimensional growth rates for the
present compressible swirling-jet cases are still less than those of
their incompressible counterparts.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
66 articles.
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