This paper investigates an isothermal free water jet discharging horizontally from a circular nozzle $(9mm)$ into a stationary body of water. The jet exit velocity was $2.5m∕s$ and the exit Reynolds number was 22,500. The large-scale structures in the far field were investigated by performing a proper orthogonal decomposition (POD) analysis of the velocity field obtained using a particle image velocimetry system. The number of modes used for the POD reconstruction of the velocity fields was selected to recover 40% of the turbulent kinetic energy. A vortex identification algorithm was then employed to quantify the size, circulation, and direction of rotation of the exposed vortices. A statistical analysis of the distribution of number, size, and strength of the identified vortices was carried out to explore the characteristics of the coherent structures. The results clearly reveal that a substantial number of vortical structures of both rotational directions exist in the far-field region of the jet. The number of vortices decreases in the axial direction, while their size increases. The mean circulation magnitude is preserved in the axial direction. The results also indicate that the circulation magnitude is directly proportional to the square of the vortex radius and the constant of proportionality is a function of the axial location.

1.
Abramovich
,
G. N.
, 1963,
The Theory of Turbulent Jets
,
MIT
,
Cambridge
.
2.
Rajaratnam
,
N.
, 1976,
Turbulent Jets
,
Elsevier Scientific
,
Amsterdam
.
3.
Tso
,
J.
,
Kovasznay
,
L. S. G.
, and
Hussain
,
A. K. M. F.
, 1981, “
Search for Large-Scale Coherent Structures in the Nearly Self-Preserving Region of a Turbulent Axisymmetric Jet
,”
ASME Trans. J. Fluids Eng.
0098-2202,
103
, pp.
503
508
.
4.
Tso
,
J.
, and
Hussain
,
F.
, 1989, “
Organized Motions in Fully Developed Turbulent Axisymmetric Jet
,”
J. Fluid Mech.
0022-1120,
203
, pp.
425
448
.
5.
Dahm
,
W. J. A.
, and
Dimotakis
,
P. E.
, 1990, “
Mixing a Large Schmidt Number in the Self-Similar Far Field of Turbulent Jets
,”
J. Fluid Mech.
0022-1120,
217
, pp.
299
330
.
6.
Agrawal
,
A.
, and
,
A. K.
, 2002, “
Organizational Modes of Large-Scale Vortices in an Axisymmetric Turbulent Jet Flow
,”
Flow, Turbul. Combust.
1386-6184,
86
(
4
), pp.
359
377
.
7.
Agrawal
,
A.
, and
,
A. K.
, 2002, “
Properties of Vortices in the Self-Similar Turbulent Jet
,”
Exp. Fluids
0723-4864,
33
(
4
), pp.
565
577
.
8.
Holmes
,
P.
,
Lumley
,
J. L.
, and
Berkooz
,
G.
, 1996,
Turbulence, Coherent Structures, Dynamical Systems and Symmetry
,
Cambridge University Press
,
New York
.
9.
,
R. J.
,
Christensen
,
K. T.
, and
Liu
,
Z.-C.
, 2000, “
Analysis and Interpretation of Instantaneous Turbulent Velocity Fields
,”
Exp. Fluids
0723-4864,
29
, pp.
275
290
.
10.
Bi
,
W.
,
Sugii
,
Y.
,
Okamoto
,
K.
, and
,
H.
, 2003, “
Time-Resolved Proper Orthogonal Decomposition of the Near-Field Flow of a Round Jet Measured by Dynamic Particle Image Velocimetry
,”
Meas. Sci. Technol.
0957-0233,
14
, pp.
L1
L5
.
11.
Barker
,
J. M.
, 1998, “
Flow Structure Dynamics of an Impinging Elliptic Jet
,” Ph.D. thesis, Clemson University, Clemson, South Carolina.
12.
Shinneeb
,
A.-M.
,
Bugg
,
J. D.
, and
Balachandar
,
R.
, 2002, “
PIV Measurements in a Confined Jet
,”
In American Society of Mechanical Engineering Fluids Engineering Division Summer Meeting
, Vol.
257
(
2A
), pp.
87
93
.
13.
Shinneeb
,
A.-M.
, 2006, “
Confinement Effects in Shallow Water Jets
14.
Hart
,
D.
, 2000, “
PIV Error Correction
,”
Exp. Fluids
0723-4864,
29
, pp.
13
22
.
15.
Liang
,
D.
,
Jiang
,
C.
, and
Li
,
Y.
, 2003, “
Cellular Neural Network to Detect Spurious Vectors in PIV Data
,”
Exp. Fluids
0723-4864,
34
(
1
), pp.
52
62
.
16.
Shinneeb
,
A.-M.
,
Bugg
,
J. D.
, and
Balachandar
,
R.
, 2004, “
Variable Threshold Outlier Identification in PIV Data
,”
Meas. Sci. Technol.
0957-0233,
15
, pp.
1722
1732
.
17.
Stanislas
,
M.
,
Okamoto
,
K.
,
Kähler
,
C. J.
, and
Westerweel
,
J.
, 2005, “
Main Results of the Second International PIV Challenge
,”
Exp. Fluids
0723-4864,
39
, pp.
170
191
.
18.
Sirovich
,
L.
, 1987, “
Turbulence and the Dynamics of Coherent Structures. Part I: Coherent Structures
,”
Q. Appl. Math.
0033-569X,
45
(
3
),
561
571
.
19.
Robinson
,
S. K.
, 1991, “
Coherent Motions in the Turbulent Boundary Layer
,”
Annu. Rev. Fluid Mech.
0066-4189,
23
, pp.
601
639
.
20.
Ganapathhisubramani
,
B.
,
Longmire
,
E. K.
, and
Marusic
,
I.
, 2002, “
Investigation of Three Dimensionality in the Near Field of a Round Jet Using Stereo PIV
,”
J. Turbul.
1468-5248,
3
, pp.
1
10
.
21.
Bugg
,
J. D.
, and
Rezkallah
,
K. S.
, 1998, “
An Analysis of Noise in PIV Images
,”
J. Visualization
1343-8875,
1
(
2
), pp.
217
226
.
22.
Agrawal
,
A.
, and
,
A. K.
, 2003, “
Measurements Within Vortex Cores in a Turbulent Jet
,”
ASME Trans. J. Fluids Eng.
0098-2202,
125
(
3
), pp.
561
568
.
23.
Press
,
W. H.
,
Teukolosky
,
S. A.
,
Vetterling
,
W. T.
, and
Flannery
,
B. P.
, 1998,
Numerical Recipes in C
,
2nd ed.
,
Cambridge University Press
,
Cambridge, NY
.