Proceedings of the ASME 2010 3rd Joint US-European Fluids Engineering
Summerof
MeetingandasProceedings
FEDSM’10
8th International Conference
Nanochannels,
Microchannels,
Minichannels
2010 onASME
Fluids Engineering
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SummerMeeting
FEDSM-ICNMM2010
August 1-5, 2010,
Montreal, Canada
August 1-5, 2010, Montreal, Canada

FEDSM-ICNMM 2010-31139
FEDSM-ICNMM2010-PIV STUDY OF THE NEAR-FIELD REGION OF A TURBULENT ROUND JET
Ivana M. Milanovic
University of Hartford
West Hartford, CT, USA

Khaled J. Hammad
Dantec Dynamics, Inc.
Ramsey, NJ, USA

ABSTRACT
Turbulent jets have been extensively studied in the past
due to their fundamental importance and wide spread usage innumerous industrial processes to enhance momentum, heat andmass transfer. Most previous work focused on the far-field or
self-similar region of the flow. However, the initialdevelopment region, where the flow is dominated bystreamwise and large-scale, Kelvin-Helmholtz-type, structures,
received far less attention. In the current study, Particle Image
Velocimetry (PIV) was used to obtain reliable statistics in thenear-field region of a turbulent submerged jet. The jet issued
from an 84 diameter, D, long pipe which ensured fullydeveloped turbulent flow conditions at the outlet. The twodimensional flow field in the plane containing the jet axis wasmeasured in the initial 8D region, for three Reynolds numbers:
14,602, 19,135, and 24,685. The selected Reynolds numbers
overlap with the previously identified critical Reynolds number
range, 10,000-20,000, where flow characteristics of a jet
undergo a dramatic transition to a much more chaotic and wellmixed state or fully developed turbulence.

Uc
Ub
r, z
ur , u zur , u z Velocity fluctuations in r and z directions (m/s)
ur2 , u z 2 Normal Reynolds stresses (m2/s2)
uru zShear Reynolds stress (m2/s2)

ur , rms

Normalized RMS velocityur2 U c in r directionu z , rms

Normalized RMS velocity

u z 2 U c in z direction

Greek Symbols
Density
Kinematic viscosity of jet fluid (m2/s)

Vorticity normalized by 2 U b D
SubscriptscCenterlinee
Initial
j
Jet
p
Pipe
r
Radialz
VerticalNOMENCLATURE
D
H
J
L
M
Re
U

Mean centerline velocity at the pipe exit (m/s)
Pipe bulk velocity (m/s)
Cylindrical coordinates (m)Instantaneous velocity in r and z directions (m/s)

Pipe internal diameter (m)Pipe-to-plate separation distance (m)Jet momentum
Pipe length (m)Mass flow rate
Reynolds number ( U b D  )Mean velocity magnitude (m/s)

INTRODUCTION
Turbulent jet flows have a variety of technically important
applications such as cooling/heating, drying, mixing and1

1

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for the purpose of comparing four vortex identification
schemes. Vortex cores were found to form as early as x/D 
0.5. Their downstream evolution led to the vortex pairing up
and creation of larger-scale structures.
Ferdman et al. [8] reported hot-wire measurements (0 
x/D  80) of jet issuing from straight pipe and a bend at
Reynolds number of 24,000. They found that the initial growthof turbulence intensities is higher for uniform initial-velocity
profiles.
Papadopoulos and Pitts [9-10] used Rayleigh lightscattering (RLS) to examine centerline mixing behavior in thenear-field of constant and variable-density jets issuing frompipe. The initial turbulence intensity per unit area wasidentified as controlling parameter and new length scales wereintroduced.
Weisgraber and Liepman [11] used PIV to measure thedevelopment of turbulence and vorticity in the transitional
region 15  x/D  30 of jet issuing from a nozzle at Reynolds
numbers of 5,500 and 16,000. Reynolds number was shown to
influence the flow structure and the rate of jet development.
Boguslawski and Popiel [12] used cross-wire probes to
examine the structure of the free pipe jet in the initial region (0 x/D  12) at Reynolds numbers of 51,000 and 125,000.
Most comparative studies investigating the effect of inlet
profiles on jet development are done for singular Reynolds
number: Xu and Antonia [13] carried out -wire measurements
in 1  x/D  75 range at Reynolds number of 86,000; Antonia
and Zhao (2001) examined downstream effects at x/D = 0, 2,30 and 50 and Reynolds number of 37,000; Mi et al. (2001)[14-15] performed both flow visualizations using the Miescattering and -wire measurements to reveal the evolution of
the scalar field in the range 0  x/D  70 and for Reynolds
number of 16,000.
Richards and Pitts [16] used Rayleigh light scattering(RLS) to examine the effects of initial velocity profile andglobal density ratio in 10  x/D  60 range and at Reynolds
number of 4,000 and 25,000. It was shown that regardless of
the initial velocity profile, axisymmetric turbulent free jets
decay at the same rate, spread at the same half-angle, and boththe mean and RMS values collapse in a form consistent withfull self-preservation.
Computational studies in the mixing transition regime havenot been abundant either. The general experience and lessons
gained from these investigations are summarized below,
followed by a brief description of the works pertaining to thephysical characterization of the flow-field. Direct numericalsimulations (DNS) resolve all the scales of the flow; however,they are resource consuming and limited to low Reynolds
number turbulent flows in small regions. Large eddy
simulations (LES) solve for unique large eddies while theuniversal effect of the smaller eddies is modeled.
Bogey and Bailly [17] employed LES to study the nearfield (0  x/D  12) of round jet in a range of Reynolds
numbers. While the Reynolds number was shown to have achemical vapor deposition (CVD). Jet flows are also commonly
studied shear flows for the purpose of turbulence modeling.
Their practical and fundamental significance resulted in a large
volume of theoretical, experimental and numerical researchtargeting specific flow regions. Based on the characteristics ofthe velocity field the axisymmetric round jet has three regions:the near-, the intermediate- and the far-field. The near-fieldwith flow characteristics similar to those at the jet exit isusually found within 0  x/D  6. In the far-field region theflow has reached a dynamic equilibrium and properly scaled
cross-stream mean and RMS profiles collapse. Jets generally
become fully-developed or self-similar beyond x/D  25. Theintermediate or transition region lies between the near- and farfields of the jet. The near- and intermediate-fields comprise thedevelopment portion of the jet and significantly influence thedownstream evolution of the jet in its numerous applications.
The mixing of scalar is observed to change dramaticallynear a critical Reynolds number. Mixing transition for jet wascharacterized qualitatively by flow visualizations in Dimotakis
et al. [1] indicating differences in the scalar field below andabove Reynolds number of 10,000-20,000. In his review article
Dimotakis [2] relied upon scalar measurements and qualitative
observations to identify the mixing transition in jets. The notionthat a mixing transition should be universal implies existence ofa transitional Reynolds number for jet flows.
A comprehensive review of the experimental andnumerical studies performed to date on a round jet may befound in Ball and Pollard [3]. This literature survey indicated adearth of data in the near- and intermediate-fields of a round jet
for a Reynolds number range corresponding to the mixing
transition. A summary of the studies in the developing regionof axisymmetric turbulent jet relevant to the mixing transition
is now presented. The two nozzle types are commonly used togenerate jet flow: smoothly contracting (contoured) nozzles
and long pipes producing nearly uniform ‘top-hat’ and nonuniform fully-developed velocity profiles, respectively.
Fellouah et al. [4] investigated the effect of Reynolds
number on the mixing transition of a free round jet with top-hat
velocity profile. Flying and stationary hot-wire measurements
were made for Reynolds numbers of 6,000, 10,000, and 30,000
at a range of axial positions, x/D, from 0 to 25. The transition
Reynolds number was found to be above 20,000.
Shinneeb et al. [5] used particle image velocimetry (PIV)and proper orthogonal decomposition (POD) to investigate
large-scale structures in the near-field (0  x/D  2.2) of jet
with top-hat velocity profile and Reynolds number 21,900.
Jung et al. [6] carried out hot-wire measurements in thenear-field (2  x/D  6) of jet issuing from nozzle at Reynolds
numbers of 78,400, 117,600, and 156,800. The POD modes
showed the evolution of the three dimensional streamwise
velocity field from ‘volcano-type’ eruptions at x/D = 2-3 to‘propeller-like’ blade patterns where the number of blades
diminish with the downstream distance.
Ganapathisubramani et al. [7] performed PIV study ofround jet in the near-field region at Reynolds number of 19,00022Copyright © 2009 by ASME
Copyright © 2010 by ASME

significant influence on the flow characteristics, its values were
either below (10,000) or far above (400,000) the mixing
transition range proposed by Dimotakis [1-2].
Mcllwain and Pollard [18] carried out LES study in thenear-field of round free jet both with and without swirl. The jet
nozzle produced top-hat velocity profile with a Reynolds
number of 68,000.
Olsson and Fuchs [19] used LES to examine the near-fieldregion (3  x/D  9) of a confined round jet at Reynolds
numbers of 10,000, 50,000 and 500,000. Again, Reynolds
number dependence was demonstrated for values outside of therange where mixing transition takes place.
It is apparent that the database of flow characteristics in thenear- and intermediate-fields of a round jet for a Reynolds
number spanning the mixing transition regime is not complete.
The objective of the current work is to study the development
region of a submerged water jet. Two components of the mean
and RMS velocity were obtained using PIV. The twodimensional flow field in the plane containing the jet axis wasmeasured at locations between 1 and 8D downstream, for three
Reynolds numbers: 14,602, 19,135 and 24,685. A fully
developed jet inflow condition allow for assessment of
turbulence models and numerical schemes. The experimental
setup and test conditions are described next.

Fig.1 Coordinate System
PIV SYSTEM AND DATA PROCESSINGA DANTEC DYNAMICS two-dimensional PIV system
was used to measure the flow field along each r-z plane ofinterest. The system consisted of synchronization hardware forcontrolling the laser and camera, and software running on a
Windows-based platform for data acquisition, management andpost-analysis. The light source was a New-Wave Research
Pegasus® dual-head, diode-pumped Nd:YLF laser system.
Each laser head was capable of operating between 1 and 10,000
pulses per second. When fired at 1kHz, the resulting per-cavity
energy at 527nm is 10mJ. A Phantom® v210, 1 megapixel
high-speed camera capable of taking more than 2,000 framesper-second (fps) at full 1280 x 800 pixel resolution was used.
The CMOS camera has an active pixel size of 20 microns and8- and 12-bit pixel depth.
The Nd:YLF laser was fired at a frequency of 100 Hz,
yielding 200 pulses of green (527-nm wavelength) 1.5 mm
beams, each having a typical pulse duration of about 180 ns.
Light sheet forming optics mounted at the exit portal of thelaser system generated a thin, focusable light sheet by means ofa series of spherical and cylindrical lenses. A vertical divergent
light sheet was used to illuminate the full extent of themeasurement region within the cylindrical tank. The verticallight sheet was aligned to pass through the center of the pipe.
The thickness of the light sheet at the imaging plane was 1 mm.
The spatial location of the illumination system was fixed during
all the tests. The CMOS camera was placed perpendicular tothe laser sheet. The lens used was a 60-mm f2.8 Nikkor. The
imaged field of view was 153 x 96 mm, at a magnification
coefficient of 0.167.
The seeding particles used were 50 m diameter Polymide
particles having a density of 1.05 g/cm3. The seeding particles
density was close to that of the working fluid, hence theparticles were nearly neutrally buoyant in the measurement
region.
For the present set of measurements, a high accuracy
multi-pass adaptive cross-correlation technique was used toevaluate the velocity field determined from each pair of particle

EXPERIMENTAL SETUP
The closed-loop system is comprised of a water tank,pump, tube and tube mounting and positioning structure. The
rectangular glass tank used was 406 mm long, 203 mm wideand 254 mm high. The tank walls were approximately 6 mm
thick. The jet was produced using a vertical type 316 stainlesssteel precision pipe placed on the cylinder centerline with an
inner diameter D = 10.92 mm, a length L = 914.4 mm and awall thickness 0.889 mm. The length-to-diameter ratio of thepipe, L/D = 84, assured a fully developed turbulent flow
conditions at the outlet. The jet was placed 102 mm, about
9.3D, away from the side walls of the tank and 208 mm, about
19D, from the tank bottom. The filled height of the tank was
240 mm, 22D.
As shown in Fig. 1, the origin of the cylindrical r,zcoordinate system coincides with the center of the pipe right at
the exit plane and the z axis pointing vertically downward.
Measurements were performed for three different
Reynolds numbers. Three volumetric flow rates of 16.25 × 10-5
m3/s (2.58 GPM), 12.6 × 10-5 m3/s (2 GPM), 9.83 × 10-5 m3/s
(1.56 GPM), were used, resulting in fixed pipe bulk velocities,
Ub, of 1.74, 1.35, and 1.05 m/s. The corresponding kinematic
viscosities of the working fluid, tap water, were 7.68 × 10-7
(32C), 7.68 × 10-7 (32C), and 7.85 × 10-7 m2/s (32C). The
Reynolds numbers, Re  U b D  , were 24,685, 19135, and14,602.

3

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images. The signal strength was further optimized by window
off-set which minimized particle drop-outs. A sub-pixel
accuracy independent of correlation peak shape was achieved
and further minimized displacement estimate errors.
Measurement uncertainty for the used high accuracy adaptive
correlation technique is discussed extensively in Ref. 20.
The final interrogation area, IA, was 16  32 pixels with
75% overlap in both the horizontal and vertical directions. An
initial IA of 128 × 256 pixels was sequentially reduced to thefinal IA. A dynamic second-order accurate method was used tospatially offset the two IA’s during each subsequent iteration
cycle by the displacement calculated from previous steps.
During each iteration cycle, checks on the correlation’s signalto-noise, as well as, a local comparison of vector attributes withthe median value of 3  3 neighbors were used to validate andremove outliers. To remove spurious vectors, a minimum peakheight ratio (between 1st and 2nd peak) of 1.2 was used, thereby
putting more stringent conditions on peak identification for thesubsequent determination of vectors. At each measurement
condition, 2000 PIV realizations at a sampling rate of 100 Hz
were obtained and used to evaluate the mean and RMS flow
field information presented here.
The centerline axial velocities at 0.25D downstream of thenozzle, Uc = 2.06, 1.66 and 1.36 m/s, for the three Reynolds
numbers, were used to normalize reported flow field data.

1

Uz / Uc

0.8
0.6
Re1
Re2

0.4

Re3
Power Law

0.2
0

-0.5

-0.25

0

0.25

0.5

r/D

Fig. 3. Comparison between radial profiles of axial
velocity at r/D = 0.25 and power law

A comparison of Uz/Uc profiles with expected fully
developed pipe conditions as approximated by the empirical
power-law, U z U c  1  1  2r D  , is given in Fig. 3. Good1n

correlation with experimental data is achieved for 1/6th power
low velocity profile (n = 6).
The radial profiles of radial, ur , rms , and axial, u z , rms , RMS
velocities are shown in Fig. 4 (a) and (b), respectively. Close to
the pipe, ur , rms values are generally low and do not vary much
across the jet. However, u z , rms distribution increases with the
Reynolds
numberandexhibits
distinctpeaks( u z , rms  0.1, 0.08, 0.07 ) at the edge of the jet due to the

RESULTS
Figure 2 illustrates radial profiles of the mean axial andradial velocities 0.25D away from the lip of the pipe for three
Reynolds numbers: Re1 = 14,602, Re2 = 19,135, and Re3 =24,685. While all velocities are normalized by the centerline
axial velocity at the pipe exit, Uc, the axial and radial distances
are normalized by the pipe diameter, D. All shown axial
velocity distributions obtained in the near-field clearly
demonstrate flow symmetry. Furthermore, normalized profiles
collapse indicating fully developed pipe conditions.

development of the turbulent shear layer. Noticeably different
RMS value components confirm the anisotropy of the Reynolds
normal stresses. Furthermore, variations across the jet core(region defined by r  0.3D ) are rather small with a local
centerline turbulence intensity u z , rms CL  0.05, 0.04, 0.03 , oru z , rmsCL U c U b   0.06, 0.05, 0.04 , which is in good agreementwith the expected values. The location r  0.5 D can beconsidered the center of annular shear layer where the velocity
fluctuations are appreciably stronger than those found in the jet
core.

1

(a)
U r /U c , Re1
U r /U c , Re2
U r /U c , Re3
U z /U c , Re1
U z /U c , Re2
U z /U c , Re3

0.6
0.4
0.2

Re1
Re2
Re3

0.08

ur, rms

U r /U c , U z /U c

0.12

0.8

0.04

0
-1

-0.5

0

0.5

1

r/D

0

Fig. 2. The radial profiles of axial (Uz/Uc) and radial
velocity (Ur/Uc) obtained 0.25D downstream thepipe exit for three Reynolds numbers

-1

-0.5

0

0.5

1

r/D

Fig. 4. The radial profiles of RMS velocities, (a) ur , rms and(b) u z , rms , 0.25D away from the outlet for given
Reynolds numbers, Re

4

4

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velocity measurements in the present work collapse onto astraight line and exhibit a decay rate of B = 5.53 and a virtual
origin z0/D = 3.8. These constants compare well with theexisting data, as seen in the Table 1.

0.12

(b)

Re1
Re2
Re3

uz, rms

0.08

0.04

0

1

-1

-0.5

0

0.5

0.8

1

U z /U c , U r /U cr/DFig. 4. The radial profiles of RMS velocities, (a) ur , rms and(b) u z , rms , 0.25D away from the outlet for given
Reynolds numbers, Re

Figure 5 illustrates the normalized mean velocity contoursof the jet at Re3  25,000 between z/D = 0.6 and 8.3. The jet isaxisymmetric with the ‘potential core’ of approximately
uniform flow (U/Uc  0.9) below z/D = 4.4. Mean flow
quantities are now characterized with the help of Figs. 6 and 7.

0.6
U z /U c , Re1
U z /U c , Re2
U z /U c , Re3
U r /U r , Re1
U r /U c , Re2
U r /U c , Re3

0.4

0.2

0
U/U c: 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0

8

2

4

6

8

z/D

Fig. 6. Downstream evolution of the mean axial and radial
centerline velocities

7
6

Authors
Present study
Wygnanski and Fiedler [21]Mi et al. [14]

z/D

5
4
3

Table 1

1
Re3
-1

0

1

z0/D
3.8
3
3.5

B
5.53
5.7
4.48

Centerline mean velocity parameters

The radial profiles of mean axial velocity at 8 downstream
locations are shown in Fig. 7. All velocity distributions
demonstrate flow symmetry and independence of Re number.
The velocity magnitude at the last downstream location, z/D =8, is about 0.61. This is approximately 68% of the ‘potential
core’ value found at z/D = 4.4.
Next, the entrainment rate of the ambient fluid into the jet
is addressed. The estimate of the local mass flow rate
ratio, M M e , was obtained from an integral of the mean axial
velocity data

2

0
-2

z/D
<8
< 50
0-64

2

r/D

Fig. 5. Normalized mean velocity contours (U/Uc) betweenz/D = 0.6 and 8.3

Figure 6 presents the centerline axial and radial mean
velocities in the near-field region for three Reynolds numbers.
It is apparent that mean velocity is not Reynolds number
dependent. The ‘potential core’ length (U/Uc  0.9) of the jetexists up to about 4.4D. Downstream of the potential coreregion, the centerline velocity decay is typically modeled with adecay equation such as:
U b 1  z z0 (1)U c B  D D 
In this equation, z0 is the virtual origin, B is the velocity decaycoefficient, and D is the pipe diameter. The axial centerline

D 2

0 UrdrMz
Me D 2
 Urdr0(2)

z  0.25 D

where Me is the mass flow rate measured at z/D = 0.25, and D/2
is the radial location at which U/Uc  1%. The result is shown
on Fig. 8. The entrainment rate is the highest for Re2  20,000
up to z/D  7. The slope of the Re1  15,000 line, initiallysmaller than that of Re2, becomes identical downstream of z/D55

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= 5. However, entrainment rate for the case Re3  25,000 is
substantially lower than that of Re1 and Re2 throughout thenear-field region. The deviation in entrainment rates observedfor Re3 could be due to the mixing transition phenomenon
previously reported by Dimotakis [2] in the Re = 10,00020,000 range.

1.2

1(M-Me )/Me

0.8

1

z/D=8

0.5
0
1

Re1
Re2
Re3

0.6

0.4

z/D=7

0.5

0.2

0
1

z/D=6

0.5

0

0

U z /U c

1

0

z/D=5

2

4

6

z/D

8

0.5

Fig. 8. Entrainment rate of the ambient fluid for given Re

0
1

z/D=4

0.5

1

0
1

z/D=3

0.5

0.8
0
1

z/D=2

J/Je

0.5
0
1

Re1
Re2
Re3

z/D=1

0.5

0.6

0.4

0
-2

-1

0

1

2

r/D

0.2

Fig. 7. The radial profiles of mean axial velocity at
different axial positions for given Reynolds
numbers, Re

0
0

4

z/D

6

8

Contours of the axial RMS velocity obtained for Re3 
25,000 between z/D = 0.6 and 8.3 are shown in Fig. 10. Bothaxial and radial RMS velocity components exhibit distinct
peaks at r/D  0.5 and z/D  7. Turbulent flow quantities are
now characterized with the help of Figs. 11-13.

D 2

2

0

2

Fig. 9. Jet momentum ratio for given Re

Figure 9 illustrates jet momentum ratio, J J e , based on
the mean axial velocity profile measurements

0 U rdrJzJe D 2 2
 U rdr

Re1
Re2
Re3

(3)

z  0.25 D

where Je is the jet momentum measured at z/D = 0.25. In theabsence of buoyancy effects, the jet momentum is conserved up
to z/D = 6 as J J e  1 .

6

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0.1
uz, rms: 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13 0.14 0.15

(b)

8
0.08

7
6

0.06

ur, rms

z/D

5
4

0.04

3
Re1
Re2
Re3

0.02

2
1

0

Re3

0
-2

-1

0

1

0

2

r/D

Radial profiles of the axial and radial RMS velocities areshown in Figs. 12 and 13, respectively. Although both velocity
distributions exhibit similar trends, only ur , rms profiles collapse.

( u z , rms ) RMS velocities is shown in Figs. 11 (a) and (b),respectively. Axial velocity magnitudes increase with thedownstream distance and Reynolds number. Only u z , rms values
number

The maximum radial velocity magnitudes are smaller thanthose of the axial counterparts. The symmetric ur , rms peaks

while

become less distinct for z/D > 6 and the relatively flat
distribution around the centerline is seen in the lastmeasurement plane. Axial velocity peaks are clearly present at
z/D = 6, with remains still visible at the next downstream
location. The last measurement plane has just one distinct
u z , rms maximum at the centerline.

0.16

(a)

0.14

0.12

CONCLUSIONSA PIV study of the near-field region of a turbulent roundwater jet issuing from a fully developed pipe flow has been
conducted. The two-dimensional flow-field in the plane
containing the jet axis was measured in the initial 8D region,
for three Reynolds numbers: 14,602, 19,135, and 24,685. The
selected Reynolds numbers overlap with the previously
identified critical Reynolds number range, 10,000-20,000,
where flow characteristics of a jet undergo a dramatic transition
to a much more chaotic and well-mixed state or fully developed
turbulence. Data have been presented for the mean and RMS
axial and radial velocity profiles. The downstream variation of
the mean axial and radial velocities and ur , rms is independent ofuz, rms

0.1

0.08

0.06

0.04

Re1
Re2
Re3

0.02

0
0

2

8

Reynolds numbers, Re

The evolution of the centerline radial ( ur , rms ) and axial

Reynolds

6

Fig.11. Downstream evolution of the RMS velocities, (a)u z , rms , and (b) ur , rms along the centerline for givenz/D = 0.6 and 8.3

the

4

z/D

Fig. 10. Contours of the axial RMS velocity, u z , rms , between

depend substantially on
ur , rms distributions collapse.

2

4

6

8

z/D

Fig.11. Downstream evolution of the RMS velocities, (a)u z , rms , and (b) ur , rms along the centerline for given

the Reynolds number. However, the axial RMS component,u z , rms , was found to substantially increase with the Reynolds

Reynolds numbers, Re

number. The entrainment rate is the highest for Re2  20,000,
while the observed deviation for Re3  25,000 could be due tothe mixing transition in the critical Reynolds number range.

7

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0.15

z/D=8

0.08

z/D=8

0.1

0.04

0.05

0.1

0

0

0.15

0.08

z/D=7

z/D=7

0.04

0.05

0

0

0.15

z/D=6

0.08

z/D=6

0.1

0.04

0.05

z/D=5

ur, rmsuz, rms

0.1

0

0

0.15

0.05

0.08

z/D=5

0.04
0

0

0.15

z/D=4

0.08

z/D=4

0.1

0.04

0.05
0.15
0.1

0

0
0.08

z/D=3

z/D=3

0.04

0.05

0

0

0.15

z/D=2

0.08

z/D=2

0.1

0.04

0.05
0.15

0

0

Re1
Re2
Re3

z/D=1

0.1
0.05

0.08

Re1
Re2
Re3

z/D=1

0.04
0

0
-2

-1

0

1

2

-2

-1

0

1

2

r/D

r/D

Fig. 12. The radial profiles of RMS velocity, u z , rms , atFig. 13. The radial profiles of RMS velocity, ur , rms , away

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ACKNOWLEDGEMENTS
The authors are grateful to Mr. Craig Goulbourne forhelping with the experiment setup.
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8

8Copyright © 2009 by ASME
Copyright © 2010 by ASME

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99Copyright © 2009 by ASME
Copyright © 2010 by ASME