Proceedings of the
4th JSME-KSME Thermal Engineering Conference
October 1-6, 2000, Kobe, Japan
Simultaneous Velocity and Concentration Measurements in a
Turbulent Jet Flow by Using PIV-PLIF Combined System
Hui HU, Tetsuo SAGA, Toshio KOBAYASHI, Nobuyuki TANIGUCHI
Yin CHEN, Seonghwan CHIO and Kazuaki NARAHARA
Institute of Industrial Science, University of Tokyo
7-22-1 Roppongi, Minato-Ku, Tokyo 106-8558, Japan
ABSTRACT A method for the simultaneous measurements of velocity and passive scalar concentration
fields by means of Particle Image Velocimetry (PIV) and Planar Laser Induced Florescence (PLIF) techniques
will be described in the present paper. Details of the implementation of the PIV-PLIF combined system are
given and the system is applied to do simultaneous measurements of velocity and concentration in the near
field of a turbulent jet flow. The ensemble averaged velocity and concentration, turbulent velocity fluctuation,
concentration standard deviation and the correlation terms between the fluctuating velocities and
concentrations in the turbulent jet flow will be analyzed based on the simultaneous measurement results in the
downstream of the turbulent jet flow.
Keywords:
PIV technique, PLIF technique, PIV-PLIF combined System, Simultaneous measurements of
velocity and concentration field, Turbulent jet flow.
1. INTRODUCTION
Simultaneous information of a passive scalar and
velocity field is desirable in many fluid flow investigations
like mixing in combustion chambers or distributions of
drugs in biomedical applications. The possibility of
measuring velocity and a scalar at the same time with a
high spatial and/or temporal resolution is also of
fundamental importance for the validation and development
of models of turbulence and turbulent mixing. For example,
in turbulent jet mixing flows, the species concentration field
ξ is determined by molecular diffusion and transported by
the turbulent flow field. When considering the Reynoldsaveraged scalar conservation equation, the effects of
turbulent transport appear in terms of the correlation
between the concentration and velocity fluctuations, i.e.
expressions such as u 'ξ ' and v' ξ ' . Experimental
characterization of these correlation terms is need for the
development and validation of physical models, and this
requires the simultaneous measurements of the velocity and
concentration fields.
Scalar quantities, such as tracer concentration or
temperature, are also often used to visualize flow parterres
and infer general flow structures. A good example is the use
of fluorescent tracers along with laser induced fluorescence
(LIF) for visualization of liquid or gas phase flows. LIF
images are routinely used to make inference about the
vortical structures and their dynamics in various flow
phenomena, even though it is known that such inference
can sometimes be misleading. The ability to simultaneously
visualize the flow structure and measure its underlying
velocity/vorticity field would serve as a valuable tool in
discovering and understanding of flow physics.
There exists an extensive body of literature on the
measurements of either velocity component or scalar
quantitative (e.g. temperature, concentration) in many types
of flows. Studies involving simultaneous velocity and scalar
measurements are far more limited. One of the earliest was
study of helium jet by Keagy & Weller [1] where they
measured the profiles of mean velocity using a Pitot probe
and mean concentration using a sampling probe. Way &
Libby [2] developed a two-sensor hot-wire probe capable of
monitoring fluctuations of both one velocity component and
concentration in a low-speed helium jet. Chavray & Tutu
[3] produced results involving two fluctuating velocity
components and temperature fluctuations using a cold-wire
sensor mounted on a X-wire probe in heated air jets. The
investigations mentioned above provide examples of work
relaying on intrusive probes.
More recently, the advent of optical diagnostics such as
LDV, LIF and Particle Scattering techniques have provided
new opportunities for the non-intrusive simultaneous
acquisition of multiple flow variables. Owen [4] used a
combination LDV and LIF to measure velocity and
concentration correlation in a co-axial liquid jet. Dibble and
Schefer [5] acquired velocity, density and species
concentration via LDV/Mie scattering and LDV/Raman
scattering, respectively, in a diffusions flame. Similar to the
earlier work of Owen, Lemoine et al. [6] obtained
simultaneous velocity and concentration data using LDV
and LIF in a co-flowing liquid jet. All of these
investigations, however, have incorporated single point
measurements.
With the rapid development of modern optical
techniques and digital image processing techniques, wholefield optical diagnostics, such as Particle Imaging Velocity
(PIV) and Planar Laser Induced Fluorescence (PLIF)
techniques, are assuming an ever-expending role in the
diagnostic probing of fluid mechanics. The advances of PIV
and PLIF techniques in the recent two decades have lead
them to be mature techniques for the whole-field
measurements of velocity and concentration or/and
temperature in a plane or over a volume of objective fluid
flow. The aim of this study was to develop a high-resolution
simultaneous velocity and concentration field measurement
system for flow diagnostics. The work described in the
present paper combines the Particle Imaging Velocity (PIV)
and Planar Laser Induced Fluorescence (PLIF) techniques
for the simultaneous measurements of instantaneous spatial
distribution of velocity and concentration, respectively.
2. EXPERIMENTAL SETUP
Figure 1 shows the schematically experimental set-up
used in the present research. The test circular nozzle
(D=30mm) was fixed in the middle of a water tank
(600mm*600mm*1000mm). Fluorescent dye (Rhodamine
B) for PLIF or PIV tracers (hollow glass particles d=8-
12µm) was premixed with water in a jet supply tank, and jet
flow was supplied by a pump. The flow rate of the jet flow,
which was used to calculate the representative velocity and
Reynolds numbers, was measured by a flow meter. A
cylindrical plenum chamber with comb structures was
installed at the upstream of test nozzles to insure the
turbulent levels of the core jet flows at the exit of test
nozzles were less than 3%. An overflow system was used to
keep the water level in the test tank to be constant during
the experiment. In the present study, the investigation
region is at the near field of the jet flow (Y/D<5.0). The
distance between the exit of the test nozzle and the free
surface of the water in the test tank is about 30D. Therefore,
the effect of the water free surface in the test tank on the
vortex structures in the near field of the jet flow is
negligible and the jet flow exhausted from the test nozzle is
considered to be a free jet flow.
The pulsed illumination laser sheet was generated by a
double-pulsed Nd:YAG Laser system (Quantel Inc.). After
passing through a second harmonic generator cell, the
wavelength of the light beams emitted from the doublepulsed Nd:YAG Laser system is 532nm. By using a set of
optics (cylindrical lens and mirrors), the laser beam was
bundled in a planar laser sheet with thickness being about
1.5 mm. The frequency of the double-pulsed illumination is
10 Hz. The pulsed illumination duration is 4ns, and power
is 200 mJ/pulse. The time interval between the two pulses
can be adjustable, which was 3 ms for the present study.
Laser sheet water tank
low pass optical filter
mixing region
Beam splitter
Double-pulsed Nd:YAG Laser
mirror
CCD camera #2
High pass optical filter for PLIF
Overflow system
A cylindrical
plenum chamber
reserve tank
for PIV
CCD camera #1
jet supply tank
Test nozzle
synchronizer
pump
Flowmeter
Figure 1. Experimental system setup
Figure 2. The photo of the PIV-PLIF simultaneous image recording system
In order to achieve the simultaneous measurements of the
concentration and velocity fields by using PLIF and PIV
techniques, a simultaneous image recording system was
designed by using optics and two high-resolution CCD
cameras (TSI PIVCAM10-30, 1K by 1K resolution). The
diagram of the simultaneous image recording system was
shown on the right upper corner of the Figure 1
schematically and the photo of the image recording system
was given on Figure 2.
Rhodamine B was used as fluorescent dye in the present
study. It was known that the emission peak of Rhodamine B
is about 590nm, and the wavelength of the illuminating
laser light scattered by the PIV tracer particles is 532nm.
Two kinds of optical filters were used in the present study
to separate the LIF lights from scattered laser lights, and
then recorded them separately to obtain PLIF and PIV
image simultaneously. As shown in the right upper corner
of the Figure 1, the combined light including both LIF light
(peak at 590nm) and scattered laser light (532nm) were
divided into two light beams by using a beam splitter. Once
light beam is go straight to CCD camera #1 for PIV image
recording. A band pass optical filter (532nm±5) was
installed at the head of the camera #1. Therefore, only the
scattered laser light is transmissible to form PIV image on
the CCD sensor of the camera #1, and the LIF light is
blocked out. Another light beam from the beam splitter was
reflected by a mirror before it enter into the camera #2 for
PLIF image recording. A high pass filter (>580nm pass)
was installed in the head of the camera #2 to filter out the
scattered laser light (wavelength 523nm). The LIF light
(peak at 590nm) pass through the optical filter to generate
LIF image on the CCD censor of the camera #2. The two
CCD cameras were mounted on a mini- optical bed, and the
positions of the two cameras were adjusted meticulously to
get the same magnification and maximum overlap view for
the two cameras. Such arrangement may also simplify the
position calibration for the two image recording cameras.
The double-pulsed Nd:YAG Laser and the simultaneous
image recording cameras were connected to a host
computer via a synchronizer (LaserPulse TSI INC.), which
controls the timing of laser illumination and image
acquisition. The host computer is composed of two highspeed CPU (800MHz, Pentium III CPU), colossal image
memory and Hard disk (1GB RAM, Hard Disk 100GB). It
can acquire the continuous image pairs up to 250 frames
every time at the framing frequency of 10 Hz.
Figure 3 shows an example of the PLIF and PIV original
images captured simultaneously by the camera #1 and #2. It
can be seen that the scattered laser light and PLIF light can
be separated successfully by using the simultaneous image
recording system shown on the Figure 2.
The diameter of the circular nozzle used in the present
study was D=30mm. The core jet velocities (U0) at the exit
of the test nozzle was about 0.20m/s. The Reynolds
numbers of the jet flows, based on the nozzle exit diameter
and the core jet velocities was about 6,000 for the present
study.
3. IMAGE PROCESSING
3.1 PIV image processing
At the current stage, the most widely used methods for
PIV image processing can be fall into two categories, i.e.,
the particle tracking methods and spatial correlation
analysis methods (including auto-correlation method and
cross-correlation method). The particle tracking methods
are based on the tracking of individual particles with the
time sequence, and vectors are obtained at random points in
space. Since most of the particles tracking algorithms rely
on the assumption that nearest neighboring images belong
to the same particles, and this is not valid if the particle
image density becomes too high. So, the particle tracking
methods are normally limited to relatively low particle
image density. Hence, it always provides poor spatial
resolution.
Rather than tracking individual particles, an improved
spatial correlation analysis method, named as Hierarchical
Recursive PIV method, was used in the present study to
conducted PIV image processing. It was well known that
the obtained velocity vector is actual the spatially averaged
displacement of the particles included in each interrogation
a. PIV image from camera #1
b. PLIF image from camera #2
Figure 3. The simultaneous images captured by the
simultaneous image recording system
window by using spatial correlation method. Any
information on the velocity fluctuations and the rotational
component of the velocity field within the region of the
flows covered by the interrogation windows is lost in the
computational process. Therefore, the spatial resolution of
the PIV result can be achieved is directly related to the size
of the interrogation windows. In order to improve the
spatial resolution of PIV results by using spatial correlation
method, the interrogation window size should be as small
as possible.
However, according to the research of Keane and
Adrian [7], at least ten tracer particle images per
interrogation window should be satisfied in order to resolve
the local particle displacement accurately by using the
conventional correlation analysis based image-processing
algorithms. Hu et al. [8] had also suggested that the
optimum particle number in an interrogation window is
about 10-20 for the conventional cross-correlation method.
These indicate that interrogation window size should be
large enough to contain sufficient number of particle
images to insure a high probability of uniqueness of the
solution by using conventional correlation based PIV image
processing methods.
The recent research of the authors had shown that, if a
prior information of the local displacement is known, even
by using a smaller interrogation window could get the
statistically meaningful PIV results. An improved
correlation based PIV image processing method, named as
Hierarchical Recursive PIV method, has been developed by
the authors [9]. The Hierarchical Recursive PIV method is
actual a hierarchical recursive process of conventional
spatial correlation method. The recursive operation started
with a large interrogation window size and search distance,
which is as the same as conventional correlation analysis
based PIV image processing methods. By using the results
of former iteration step as the approximate offset values in
the next iteration step, the interrogation window size and
search distance were reduced hierarchically. The
conventional correlation method always used 64 by 64
pixel or 32 by 32 interrogation windows, the hierarchical
recursive PIV method can reduce the final interrogation
window up to 8 by 8 pixel with spurious vectors being less
than 2%.
3.2 PLIF Image processing
Following Coppeta et al. [10], the intensity of the laser
induced fluorescence light at any arbitrary point (x0,y0)
along the excitation beam for unsaturated excitation can be
expressed as:
(1)
H f ( x 0 , y 0 ) = I ( x 0 , y 0 ) A Φ ε L ξ ( x0 , y 0 )
Where Hf ( x0,y0) is the detected fluorescence intensity at
the measurement point (x0, y0), A is the fraction of the
fluorescence light collected by camera. Φ is the quantum
efficiency, L is the length of the sampling volume along the
path of excitation beam, ε is molar absorptivity, and
ξ(x0,y0) is the molar concentration of the fluorescent dye.
I(x0,y0) is the intensity of excitation light beam at the
measurement point (x0,y0).
It was known that the intensity of the excitation light
I(x0,y0) is the function of the position and the concentration
distribution of the fluorescent dye along the excitation
beam before reaching the measurement point (x0,y0). The
concentration distribution of the fluorescent dye may
attenuate the intensity of the excitation beam. This
attenuation effect will be increasing with the increasing of
the concentration of the fluorescent dye [11]. In order to
avoid the attenuation effect, the low fluorescent dye
concentration solution (0.3mg/l) is used for the present LIF
experiment.
From the equation (1), it can be seen that the intensity of
induced fluorescent light detected by the image recording
camera will be changed linearly with the concentration of
the fluorescent dye for the constant properties of carrier
flow (temperature, oxygen content, pH value etc.) when the
attenuation effect is negligible. Such linear relationship had
been reported in previous research [11].
In order to obtain whole field quantitative concentration
distribution in flow field, the calibration procedure to
account for laser sheet non-uniformity had been conducted
in the present study. For fixed optical setting, the linear
relationship between the concentration field ξ(x,y) in the
objective fluid flow and the digital signal level id(x,y) can
be expressed by the following equation:
id ( x, y ) − idb ( x, y ) = k ( x, y )ξ ( x, y )
(2)
where the k(x,y) in the above equation included
variations in laser energy over the illuminating laser sheet.
idb(x,y) is the backgroud emission.
In order to calibarate th effect of laser sheet nonuniformity, the background emission idb(x,y) is determined
firstly by taking 50 images of objective field without LIF
dye but with scattering PIV particle and illuminating laser
running. Then, the mean digital signal level idξ0(x,y) with
known uniform concentration (ξ0=0.3mg/l) in the
measurement region is determined by 50 images.
According to the equation (2), the following equation can
be got:
idζ 0 ( x, y ) − i db ( x, y ) = k ( x, y )ξ 0 ( x, y )
(3)
Therefore, the normalized concentration distribution in
the measurement field is obtained by following equation:
ξ ( x, y )
ξ 0 ( x, y )
k ( x, y )ξ ( x, y )
=
k (x, y )ξ 0 ( x, y )
idζ ( x, y ) − idb ( x, y )
=
idζ ( x, y ) − idb ( x, y )
c ( x, y ) =
(4)
0
Once the velocity and concentration fields were
calculated, it is relatively straightforward to calculate the
various ensemble-averaged velocity ( U , V ), turbulent
velocity
fluctuations
averaged
concentration
'
'
( (u ' u ' ) , (v ' v ' ) ),
(C),
concentration
ensemblestandard
deviation ( c c ) and the turbulent flux terms ( u ' c ' , v ' c ' )
which is the correlation terms between the velocity and
concentration.
In the present study, 250 consecutive PIV and PLIF image
pairs captured simultaneously by the image recording
system at the frame rate of 10Hz were used to calculate
above ensemble-averaged values.
Since the spatial resolution of PIV results is determined
by the sizes of the interrogation window used for
correlation operation. The final interogation window size is
8 by 8 pixel for the present study, so the concentration data
4.5
4
Y/D
3.5
0.25 m/s
3
2.5
2
1.5
1
-2
-1
0
1
2
X/D
Figure 4. The instantanous results of the PIV measurement
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spanwise vorticity
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135.00
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downstream of the turbulent jet flow. They were found to
almost same order from the measurement results.
10
v ' c ' and radial turbulent flux u ' c ' at 2D, 3D and 4D
v ' c ' and radial turbulent flux u ' c ' were found to be
10
190
4. EXPERIMENTAL RESULTS AND DISCUSSIONS
Figure 4 shows an example of the instantaneous PIV
result obtained by processing a PIV image pair with
Hierarchical Recursive PIV method. The final interrogation
window size is 8 by 8 pixel, so, about 50,000 vectors can be
got for every instantaneous PIV result. Only the 25% of the
velocity vectors were shown on the Figure 4. Figure 5
shows the vorticity distribution calculated based on the
instantaneous velocity vector field shown on Figure 4.
Figure 6 shows the instantaneous concentration field
obtained by PLIF image processing, which is the
simultaneous measurement result of the PIV results shown
on Figure 4 and Figure 5. The contour levels given in the
figure represent Rhodamine B concentration levels
normalized by the jet source concentration ξ0 =0.3mg/l.
This PLIF measurement result is quite similar to the LIF
visualization results reported by Liepmann and Gharib [12].
It was well known that the shear layer origin form the exit
of the test nozzle is invisicidly unstable via KelvinHelmholtz primary instability for the circular jet flow. The
instability grows downstream and rolled up into coherent
vortex rings. The vortex ring structures merge as they move
downstream and then break down into small vortex
structures. The transition of the jet flow into turbulence
occurs when the large vortex rings break down into small
scale vortices. All these processes can be seen clearly from
both the PIV and PLIF simultaneous measurement results
given in these figures.
Figure 7 shows the profiles of various ensemble-averaged
flow parameters in the three downstream locations of the
turbulent jet flow. These ensemble-averaged parameters
were calculated based on 250 instantaneous PIV and PLIF
measurement results, and normalized with the core jet
velocity U0=0.20 m/s and jet source concentration ξ0=0.3
mg/l. In order to verify the present PIV and PLIF
simultaneous measurement results, the measurement results
of Lemoine et al. [6] by using single point measurement
techniques LDV and LIF at 4D downstream of the circular
jet flow had also been given on the profiles of the
ensemble-averaged axial velocity(Figure 7(a)) and mean
concentration(Figure 7(b)). From the comparisons, It can be
seen that the present PIV and PLIF simultaneous
measurement results agreed with the measurement results of
Lemoine et al. [6] well.
Figure 7(c) and Figure 7(d) show the profiles of the axial
velocity fluctuation and concentration standard deviation at
2D, 3D and 4D downstream of the turbulent jet flow. The
regions with high fluctuation values in these profiles are
corresponded to the shear layers between the core jet flow
and ambient flow. It can be seen that as the downstream
distance increasing, the width of the shear layer increased,
so the regions with high fluctuation values also increased.
Figure 7(e) and Figure 7(f) give the axial turbulent flux
be the same bell-shapeded profiles. Although the axial
velocity component is much bigger than the radial velocity
component in the circular jet flow, the axial turbulent flux
9
1
-2
-1
0
1
2
X/D
Figure 5. The instantanous spanwise vorticicity distribution
5
concentration
1.00
0.95
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Y/D
were also averaged over 8 by 8 subwindows during the
PLIF image processing. About the accurecy level of the
present measurement result of velocity and concentration,
the uncertainty of PIV result is supposed to be less than 2%
and 5% for the PLIF concentration measurement result.
3
2.5
2
1.5
-2
-1
0
1
2
X/D
Figure 6. the instantanous measurement result by using
PLIFtechnqiue
0.25
1.2
1.2
ensemble-averaged concentration, C
ensemble-averaged axial velocity V
1
1
0.8
0.8
2D
3D
4D
lemoine et al.
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axial velocity fluctuation
0.20
2D
3D
4D
lemoine et al.
0.6
0.15
0.10
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0.2
0.00
0
0
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1
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a. The ensemble averged axial velocity
0.40
c 'c '
0.30
0
0.5
1
0.15
0.0
0.5
1.0
1.5
2.0
0.035
radical turbulent flux
0.10
0.05
v 'c '
0.025
0.010
2D
0.020
0.005
3D
4D
0.015
2D
3D
4D
0.010
0.005
0.000
0.00
axial turbulent flux
0.030
' '
uc
2D
3D
4D
0.20
2
0.020
0.015
0.25
1.5
b. The ensemble averaged concentration c. The axial velocity fluctuation
Concentration standard deviation
0.35
2D
3D
4D
0.4
0.2
0
' '
(u u )
0.000
-0.05
0.0
0.5
1.0
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2.0
0.0
-0.005
0
0.5
1
1.5
2
0.5
1.0
1.5
2.0
-0.005
d. Concentration standard deviation
e. The radial turbulent flux f. The axial turbulent flux
Figure 7. The ensemble averaged measurement results
5. SUMMARY AND CONCLUSIONS
A system has been developed to conduct the velocity and
concentration simultaneous measurements of the fluid flow
by using Particle Image Velocimetry (PIV) and Planar
Laser Induced Fluorescence (PLIF) techniques. The
objective fluid flow was illuminated by a double pulsed
Nd:YAG laser, and Rhodamine B was used as fluorescent
dye premixed in the flow field. The LIF lights and scattered
illuminating laser lights were separated successfully by
using two kinds of optical filters, and recorded
simultaneously by two high-resolution CCD cameras. The
system was used to measure velocity and concentration
distributions in the near field of a circular jet flow
simultaneously. The measurement results of the present
system were compared with the previous point
measurement results to benchmark the present system. As a
result of these comparisons, it was concluded that the
present combined PIV and PLIF measurement system is
effective and efficient to conduct the velocity and
concentration simultaneous measurements of the fluid flow.
6. REFERENCES
1. Keagy, W. R. and Weller, A. E. A Study of freely
expanding inhomogeneous jets, Proc. Heat Transfer.
Fluid Mechanics Inst., Vol.1-3, (1949), pp89-98.
2. Way, J. and Libby, P. A. Hot-wire Probes for measuring
velocity and concentration in helium and air mixture.
AIAA Journal. (1970), Vol.8, pp976-978.
3. Chevary, R. and Tutu, N. K. Intermittence and
Preferential Transport of Heat in a Round Jet. Journal of
Fluid Mechanics, Vol.88, (1978), pp 133-160.
4. Owen, F. K., Simultaneous laser measurements of
instantaneous velocity and Concentration in Turbulent
Mixing Flows, Proceeding of AGARD Conference On
Applications of Non-Intrusive Instrumentation in Fluid
Flow Research. (1976), AGARD-CP-193.
5. Dibble, R. W. and Schefer, R. W. Simultaneous
Measurements of Velocity and Scalars in a Turbulent
Non-promixed flame by Combined Laser Doppler
Velocimetry and Laser Raman Scattering, Proceedings
of 4th Turbulent Shear Flows, (1983), Karlsruhe,
Germany, September 12-14.
6. Lemoine F., Wolff M. and Lebouche M. Simultaneous
concentration and Velocity Measurements Using
Combined Laser-Induced Fluorescence and Laser
Doppler Velocimetry: Application to Turbulent
Transport, Experiments in Fluids, (1996) Vol.20, pp341327.
7. Keane R. D. and Adrian R J. Optimization of Particle
Image Velocimetry, Measurement Science and
Technology, Vol.2. (1990), pp1202-1215.
8. Hu H., Saga, T., Kobayashi T., Okamoto K. and
Taniguchi N., Evaluation of the Cross Correlation
Method by Using PIV Standard Images, Journal of
Visualization, Vol.1, No.1 (1998), pp87-94.
9. Hu H., Saga T., Kobayashi T., Taniguchi N. and Segawa
S., The Spatial Resolution Improvement of PIV Result
by Using Hierarchical Recursive Operation, to be
published on the Journal of Visualization. (2000).
10. Coppeta J. and Rogers C., Dual emission laser Induced
Fluorescence for Direct Planar scalar behavior
measurements, Experiments in Fluids, Vol.25 No. 1,
(1998), pp1-15.
11. Hu H., Kobayashi T., Wu S. and Shen G., Research on
the Vortical and Turbulent Structure Changes of Jet Flow
by Mechanical Tabs. Journal of Mechanical Engineering
Science (U.K.) Vol. 213 (1999), pp321-329.
12. Liepmann, D. and Gharib, M., The Role of Streamwise
Vorticity in the Near Field Entrainment of Round Jets.
Journal of Fluid Mechanics. (1992), Vol.254. 643-668.