Author:
KARASSO P. S.,MUNGAL M. G.
Abstract
The concentration field of mixing layers subject to stabilizing
and
destabilizing
streamwise curvature was investigated at post-mixing-transition conditions.
A set of
operating conditions was implemented, identical to those at which straight
layers
were previously investigated in the same facility, in order to compare
the effects
of hydrodynamic instabilities upon scalar mixing. Quantitative imaging
of planar
laser-induced fluorescence was used for (i) passive scalar measurements,
and (ii)
chemical product measurements. Similar to the straight mixing layer, the
results
for the curved layers show that beyond the mixing transition the layer
continues
to evolve, and undergoes a small change in its scalar structure. At conditions
just
past the mixing transition both stable and unstable layers have average
mixed-fluid compositions
which are uniform across the layer, and average chemical product concentration
profiles which are symmetric. At more fully developed conditions, the scalar
field
evolved: the average mixed-fluid concentration developed a small lateral
variation,
while the chemical product concentration profiles became asymmetric. Similar
to the
straight layer, the mixture-fraction PDF is believed to be of the tilted
type for
the most fully developed layer examined, with the marching PDF being a
poor
representation. Consistent with previous investigations, the growth rate
of the
unstable layer was found to be higher than that of straight or stable layers.
The
most important result is that the measured mixing efficiency of all the
layers
(curved and straight) was found to
be the same: both the total mixed-fluid composition, and the volume fraction
of
mixed fluid were the same for all unstable, stable, and straight layers.
The amount
of mixed fluid (and of chemical product formed) was larger for the unstable
layer,
but always in a fixed proportion to the layer's thickness. The lack
of
increase in the mixing efficiency for the unstable layer is surprising,
given
that previous hydrodynamic measurements
had shown enhanced turbulent transport for the unstable case. Thus, for
all liquid
shear layers studied, the rate of scalar mixing appears to be directly
proportional
to the entrainment rate (which essentially determines the layer's
growth
rate), and not to any hydrodynamic measures.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
9 articles.
订阅此论文施引文献
订阅此论文施引文献，注册后可以免费订阅5篇论文的施引文献，订阅后可以查看论文全部施引文献