This paper presents quantitative imaging measurements of jet fluid mole fraction fields in turbulent buoyant jets of helium issuing into air. The measurements use planar laser Rayleigh scattering. Signal levels are low, necessitating a novel approach to background subtraction in the signal processing. The jet flows considered are classified as momentum-driven, meaning that buoyancy effects are presumed to be confined to the small scales of the flow. We focus here on the near-nozzle, developing region of the jet, which is of particular interest to flows with combustion. The results suggest that buoyancy affects the details of the evolution of the mixing field even while the mean field maintains scaling properties consistent with non-buoyant jets. Specifically, the mean jet fluid mole fraction profiles show a sharper jet/ambient fluid interface relative to non-buoyant jets. The mole fraction fluctuations within the jet are also weaker than those reported in non-buoyant jets. These results will inform ongoing efforts to model the mixing process in flows with density differences, such as combustion systems.

1.
Ricou
F. P.
, and
Spalding
D. B.
,
1961
. “
Measurements of entrainment by axisymmetrical turbulent jets
”.
J. Fluid Mech.
,
11
, pp.
21
32
.
2.
Cetegen
B.
,
1997
. “
Behavior of naturally unstable and periodically forced axisymmetric buoyant plumes of helium and helium-air mixtures
”.
Phys. Fluids
,
9
, pp.
3742
3752
.
3.
Papantoniou
D.
, and
List
E. J.
,
1989
. “
Large-scale structure in the far field of buoyant jets
”.
J. Fluid Mech.
,
209
, pp.
151
190
.
4.
Way
J.
, and
Libby
P. A.
,
1970
. “
Hot-wire probes for measuring velocity and concentration in helium and air mixtures
”.
AIAA J.
,
8
, pp.
976
978
.
5.
Way
J.
, and
Libby
P. A.
,
1971
. “
Application of hot-wire anemometry and digital techniques to measurements in a turbulent helium jet
”.
AIAA J.
,
9
, pp.
1567
1573
.
6.
Aihara
Y.
,
Koyama
H.
, and
Morishita
E.
,
1974
. “
Effects of an air stream on turbulent diffusion of helium jet from a small nozzle
”.
Phys. Fluids
,
17
, pp.
665
673
.
7.
Panchapakesan
N. R.
, and
Lumley
J. L.
,
1993
. “
Turbulence measurements in axisymmetric jets of air and helium. Part 2: Helium jet
”.
J. Fluid Mech.
,
246
, pp.
225
247
.
8.
Zhou
X.
,
Luo
K. H.
, and
Williams
J. J. R.
,
2001
. “
Study of density effects in turbulent buoyant jets using large-eddy simulation
”.
Theoret. Comput. Fluid Dynamics
,
15
, pp.
95
120
.
9.
Sun, O. S., Su, L. K., and Burton, T. M., 2006. Joint experimental and numerical studies of subgrid scalar mixing models for les. AIAA Paper 2006–0701.
10.
Watson
K. A.
,
Lyons
K. M.
,
Donbar
J. M.
, and
Carter
C. D.
,
2003
. “
On scalar dissipation and partially premixed flame propagation
”.
Combust. Sci. and Technol.
,
175
, pp.
649
664
.
11.
Su, L. K., and Mungal, M. G., 2006. “Experimental investigation of stabilization mechanisms in turbulent, lifted jet diffusion flames”. Combust. Flame. to appear.
12.
Chen, C. J., and Rodi, W., 1980. Vertical Turbulent Buoyant Jets: A Review of Experimental Data. Pergamon, Oxford.
13.
Biringen, S., 1975. An experimental study of a turbulent axisymmetric jet issuing into a coflowing airstream. Technical Note 110, von Ka´rma´n Institute for Fluid Dynamics.
14.
Eckbreth, A., 1988. Laser Diagnostics for Combustion Temperature and Species. Abacus Press, Kent, UK.
15.
Bartels, J., et al., eds., 1962. Landolt-Bo¨rnstein Numerical Data and Functional Relationships in Science and Technology, 6th ed. Springer, Berlin.
16.
Dowling
D. R.
, and
Dimotakis
P. E.
,
1990
. “
Similarity of the concentration field of gas-phase turbulent jets
”.
J. Fluid Mech.
,
218
, pp.
109
141
.
17.
Buch
K. A.
, and
Dahm
W. J. A.
,
1998
. “
Experimental study of the fine-scale structure of conserved scalar mixing in turbulent shear flows. Part 2. Sc ≈ 1
”.
J. Fluid Mech.
,
364
, pp.
1
29
.
18.
Su
L. K.
, and
Clemens
N. T.
,
2003
. “
The structure of fine-scale scalar mixing in gas-phase planar turbulent jets
”.
J. Fluid Mech.
,
488
, pp.
1
29
.
19.
Raffel, M., Willert, C., and Kompenhans, J., 1998. Particle Image Velocimetry: A Practical Guide. Springer, Berlin.
This content is only available via PDF.
You do not currently have access to this content.