Experimental investigation of two heated oblique

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –

6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME

669

EXPERIMENTAL INVESTIGATION OF TWO HEATED OBLIQUE

JETS INTERACTING WITH A TURBULENT FLOW

Tcheukam-Toko D.*1

and Paranthöen P.2

1Department of Energetic Engineering, University Institute of Technology. P. O. Box

455, Ngaoundere, Cameroon. 2 CNRS UMR 6614 CORIA, University of Rouen. P. O. Box 12 – 76801 Saint-

Etienne du Rouvray, France

* Corresponding author. Email: [email protected]

ABSTRACT

The objective of this study is to analyse experimentally the thermal field of two air-

jets inclined at 45° interacting with a turbulent longitudinal flow. The heating of the air-jets

before their entrance simulates the passive scalar. At the outlet, the air-jets generate some

vortexes in the longitudinal flow. The measurement of temperature and fluctuations are

carried out with the help of a hot wire anemometer. The mean temperature fields and

fluctuations are represented in the 0yz plane in different positions on longitudinal axis. The

results show that the mode of the passive scalar dispersion verified previous works carried

out. The temperature fluctuations increase with the passive scalar dispersion as the jets go

away from the source.

KEYWORDS: Jets, thermal field, passive scalar, turbulent flow, temperature fluctuations,

vortex, experiments.

I. INTRODUCTION

Air pollution has become over time a worrying phenomenon in the world. One of the

factors contributing to this atmosphere pollution is the hot gas emitted by heat engines as jets.

To better understand the movement of these jets and heat dispersion in the atmosphere, it is

necessary to study its transport from the moment they are issued until their total dispersion.

Now days, many studies have been done on the dynamic aspect. In preliminary studies made

in the wake of Ahmed body, Gosse [1] showed that the velocity of the longitudinal flow

dominated the jet velocity gradually as one moves away from the source. The jets may also

be issued at an angle for generating vortices in a longitudinal flow. On this subject, Küpper

[2] used two numerical models to explain the control of boundary layer phenomena and heat

transfer at the entrance of the reactors. Tilmann [3] showed in an experimental study the

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING

AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 3, Issue 3, September - December (2012), pp. 669-681

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IJMET

© I A E M E

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976

6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep

influence that a discontinuous jet, emitted at a given frequency

experimental studies have shown that the heat contained in the jets moved in the longitudinal direction

of the flow. For example those of

directions of the scalar propagation

numerous studies, there are still gray areas including

fluctuations on the passive scalar

investigation of the thermal field of a turbulent flow interacting with two

help to understand the influence of temperature fluctuations on the

to better explain the phenomenon of air pollution. The design and construction o

made in the laboratory. The choice of h

and Anderson [5], and more recently those of Gosse [

based on the work of Bray and Garry [

jets and eddies in the longitudinal flow.

device, and then, we do an analysis of

temperature.

II. MATERIEL AND METHOD

In this study, the main flow is

circuit” which can generate flow velocities

anemometry as measurement technique

II.1 Blower type “open circuit”This blower, built by Delta Lab

centrifugal type providing a maximum flow rate of 0.

regulated by the intermediary of a variable speed transmission supplied with 220 V single

currents. The air circuit comprises a

(wire cloth) located downstream of the

the flow. In the output of the two

velocity of the flow is set between

in the order of 0.35%.

Figure 1:

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976

6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME

670

emitted at a given frequency can have on a turbulent flow. Other

tudies have shown that the heat contained in the jets moved in the longitudinal direction

of Kothnur and Clemens [4], which in addition show that the

propagation and the normal shear stress are perpendiculars

ere are still gray areas including understanding the phenomena of temperature

passive scalar dispersion. The aim of our study is to make an experimental

of a turbulent flow interacting with two heated oblique jets. This will

the influence of temperature fluctuations on the passive scalar dispersion

to better explain the phenomenon of air pollution. The design and construction of the model were

laboratory. The choice of holes diameter jet emission has been based on the work of Gibb

], and more recently those of Gosse [1]. The jets’ emissions are inclined by 45

Garry [6], this inclination is an optimal position to have good quality

jets and eddies in the longitudinal flow. To carry out this study, we first describe the experimental

do an analysis of mean temperature fields and of standard deviation of t

MATERIEL AND METHODS

In this study, the main flow is the air generated by a blower longitudinal plane

velocities (U∞), between 3m.s-1 and 12.5m.s-1. We used hot wire

technique.

Blower type “open circuit” Delta Lab, is shown in Figure 1. It consists of a motor-driven fan of the

viding a maximum flow rate of 0.32 m3.s

-1. The revolutions number of the fan is

intermediary of a variable speed transmission supplied with 220 V single

comprises a diffuser located in the rectangular fan discharge. The two

located downstream of the dust filter to reduce the level of turbulence and homogenize

two-dimensional convergent (section 80x200 mm2),

3 m.s-1and 20 m.s-1. The level of turbulence at the nozzle outlet

Figure 1: Blower type “open circuit”


Dec (2012) © IAEME

can have on a turbulent flow. Other

tudies have shown that the heat contained in the jets moved in the longitudinal direction

], which in addition show that the

s.Despite these

understanding the phenomena of temperature

dispersion. The aim of our study is to make an experimental

oblique jets. This will

dispersion in order

f the model were

n the work of Gibb

inclined by 45°,

this inclination is an optimal position to have good quality

To carry out this study, we first describe the experimental

standard deviation of the

generated by a blower longitudinal plane, type “open

We used hot wire

driven fan of the

number of the fan is

intermediary of a variable speed transmission supplied with 220 V single-phase

The two gratings

and homogenize

the maximum

at the nozzle outlet is



671

The two oblique jets are diverted 45° in a plane perpendicular to the main flow (flow

in the outlet of the nozzle) through circular holes made on a plate fixed to the lower edge of

the outlet nozzle. They have each one a diameter of 5 mm and are separate one of the other

by 40 mm as figure 2a shows it. The emission of pollutants is simulated by injecting hot air

through the two holes at a velocity Uj through a small pipe with 5 mm of diameter under the

plate as shown in Figure 2b. The temperature difference ∆Tref between the jet and the outside

is kept constant at 20°C using a regulated power supply. The thermostat of the heating system

is connected to the thermocouple control chamber. This small temperature difference avoids

effects gravitate. The velocity of the heated flow (Uj), is measured by a loss of load

connected to a micro manometer Furness Control. This velocity is adjustable between 1 and

10 m.s-1

as shown in figure 3.The origin 0 of the orthogonal axe (0x, 0y, 0z) is located

equidistant from the two holes i.e, 20 mm of each axis. The two holes are symmetrical

relative to the 0x axis oriented in the direction of the main flow. 0y axis is vertical and the 0z

axis is perpendicular to the main flow.

Figure 2: Plate; a) Front view; b) Top view Figure 3: the device of injection of the hot air

The measured variable in this study is the temperature difference between the heated

zones and upstream fluid. In this study, the sign "+" indicates a normalized quantity. Lengths

are normalized by the distance between the hole and the main axis H equal to 20 mm, and the

temperature difference is normalized by the initial temperature difference ∆Tref. Molecular

effects are negligible compared to the turbulence, the report ∆T/∆Tref can be likened to a

concentration c, will vary between 1 and 0 emission to infinity. For convenience, the time

average and standard deviation of a quantity X are denoted respectively <X> and <X'2>

1/2.

The outputs of the two jets heated are located respectively at the point S of coordinates (X+ =

0, Y+ = 0, Z

+ = -1), and S 'of coordinates (X

+ = 0, Y

+ = 0, Z

+ = 1).

II.2 Hot wire anemometry

The Measure of a velocity flow using hot wire anemometry is based on convective

heat exchange between the hot wire and the flow. This exchange is used to connect the wire

temperature to Nusselt number (Nu) which is a function of the flow velocity and the current

power I shown by the equation (1). The figure 4 below, illustrates well this principle of

convective exchange. The detail is clear in Paranthoën and Lecordier [7], and Rosset, and al

[8].



672

( )( )0 g 0

w g

g 0

R 1 T T I²T T

Nu l R I²

+ α −= +

π λ − α where,

g

hdNu =

λ. (1)

The hot wire anemometer operates at constant temperature. In this case, when the

flow velocity varies, measuring the current I needed to keep the temperature Tw of the wire,

constant. This technique provides a frequency response of approximately100 kHz.

The electrode used is a set TSI, consisting of a sensor to a wire, a processor and an

IFA conversion board 12-bit analog voltage, installed in a PC with high memory capacity and

storage. Probes conducted in the laboratory are made with platinum-rhodium10%, with 3 µm

of diameter. A schematic of the probe used is presented in figure 5.

The response of the wire as a function of the velocity is not linear. Calibration of the

hot wire placed in the outlet section of the jet; is performed before each series of

measurements by varying the velocity of the flow. An example of a calibration curve is

shown in figure 6. The experimental points are then approximated by a polynomial of

ordernor with a selected interpolation function type "Cubic Spline". The temperature of the

flow is measured by a thermocouple type K and recorded. If there are any changes in the

temperature of the flow, a correction can thus be applied to the measured voltage.

Figure 4: Schematic of hot wire

L = lengthof the wire.

D =diameter of the wire

I = electrical current

Rw = operating resistance of the hot wire at Tw

Tw = Temperature of the hot wire.

U = Flow velocity

Tg = Temperature of the surrounding air

Table 4: Legend of figure 4

Figure 5: Diagram of the hot wire probe used Figure 6: Example of a calibration curve of a

hot wire: voltage in function of the velocity

II.3 Temperature measurement The instantaneous signal T(t) of temperature can be decomposed as:

T(t) = <T> + T’(t) (2)

<T> is the temporal mean value and T'(t) is the temperature fluctuation. The signal is

characterized by a mean value <T>, and centered moments that allow access to the standard

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

0 5 10 15 20 25vitesse (m/s)

tension (V)



673

deviation <T'2>

1/2. In our case, each mean time is calculated on a sample of more than

200,000 points.

Mean temperature: N

i

i 1

1T T

N =

< >= ∑ (3)

Variance: N

2 2

i

i 1

1T ' (T T )

N =

< >= − < >∑ (4)

In the experiments of dispersion downstream from the linear sources or point sources,

the variations in temperature which one must measure quickly become relatively weak. The

temperature signal is thus influenced by the background noise as the distance from the

source. This requires making corrections to background noise to accurately measure the

actual signal. Assuming that the instantaneous value of the temperature can be written in the

following form:

Tmes (t) = <T>V + T’V (t) + T'BF (t) (5)

The subscripts “mes”, "V" and "BF" correspond respectively to the measured values, true

values and background noise values. To make the corrections of noise on the variance, we

used the following equation:

Variance: 2 2 2

V mes BFT ' T ' T '< > =< > − < > (6)

III. RESULTS AND DISCUSSION

We conducted several series of temperature measurements by choosing a single

longitudinal flow velocity Ui = 5 m/s for different jets velocities Uj, equal to 5 m/s, 10 m/s

and 20 m/s), corresponding to the Reynolds number (Re = Ud/ν), of 1200, 2400 and 4800. To

show more details, we performed measurements in the plane (Y+, Z

+) with a very small mesh.

On the Z+ axis, the scan was between -2.5 to +2.5 values with 1/20 of step of measuring. On

the Y+ axis, the scan was between 0 to 1.5 values with 1/20 of step of measuring. That makes

a total of 3,000 points of space measurements.

III.1 Means temperatures The figures 7a, 7b and 7c below represent the iso-values of mean temperature at the

positions X+ = 0.5; X

+ = 2.5 and X

+ = 5; for a jets velocity of 5 m/s (in this case, the jets

velocities are equal to the longitudinal flow velocity, (Uj equal to Ui.). These figures show

that the two jets are symmetric with respect to the axes 0X+and 0Y

+, and even when one is in

a remote position (X+ = 5). We observe a low dispersion of the passive scalar in this position

and the area of the intermediate temperature (<T> = 0.099), becomes predominant. The two

jets are still largely dominated by the longitudinal flow that prevents the plate off. The area

where the temperature is high (<T> = 0.3) remains sticking to the plate along the longitudinal

axis 0X+.

The figures 8a,8b, 8c and 8d below represent the iso-values of mean temperature in

the positions X+= 0.5; X

+ = 1, X

+= 2.5 and X

+= 5, when the jets have a Reynolds number of

2400. We note that the two jets take off from the plate upon release (X+= 0.5), and reach the

coast Y+ = 1 from the position X

+= 2.5. The size of the hottest zone (<T> = 0.3), decreases as

the distance along the longitudinal axis. It disappears almost completely at the position X+ =

5, and the intermediate zone (<T> = 0.099), becomes very dominant and invades the entire

area near the plate (Y+ =0). Coast Y+ = 1 appears as the maximum height reached by the

hottest zone of the jets. The two jets are no longer symmetrical relative to the axes 0X+and

0Y+

from the position X+= 1, also considered as the position where the scalar begins to



674

undergo a dispersion. This is very important when the jets reach the position X+ = 5, in the

area where Y+ ≤ 1, the temperature is greater than zero.

The figures 9a, 9b, 9c and 9d below represent the iso-values of mean temperature in

different positions of the plane (Y+, Z

+), for jets with a Reynolds number of 4800. We note

that the two jets are less influenced by the longitudinal flow. They quickly take off the plate

at the position X+

= 0.5 and cross the coast Y+ = 1.5 at the position X

+ = 5. The size of the

hottest zone (<T>= 0.33), decreases significantly from the position X+

= 0.5. It disappears

completely in a jet and still a bit in the other, specifically one that is close to the axis 0X+.

This shows that the scalar disperses less rapidly than in the previous case (Re = 2400). The

size of the intermediate zone (<T> = 0.099), becomes dominant and the asymmetry of the

two jets with respect to axes 0X+

and 0Y+

is even more significant.

In these three sets of measures, we note that in the case where the jets could be less

influenced by the longitudinal flow (Re= 4800), there are quick release streams of the plate

but the scalar disperses less. This is obvious for all three positions because at X+ = 5, the

temperature is <T> = 0 (dark blue) on the wall of the plate, and different from zero in the

region close to the wall for other cases Re = 1200 and Re = 2400. This heat dispersion on the

plate is translated by the shape of the isotherms which spread much on the plate.

a)

b)

c)

Figure 7:Iso-values of mean temperature fields<T>in the plane (Y+, Z

+),Re= 1200

a): X+= 0.5;b): X

+= 1; c): X

+ = 5

Z+

Y+

-2 -1 0 1 20

0.5

TEMPERATURE

0.357274

0.335275

0.313276

0.291277

0.269278

0.247279

0.225279

0.20328

0.181281

0.159282

0.137283

0.115284

0.0932846

0.0712855

0.0492863

Z+

Y+

-2 -1 0 1 20

0.5

TEMPERATURE

0.267911

0.249998

0.232085

0.214172

0.196258

0.178345

0.160432

0.142519

0.124605

0.106692

0.0887788

0.0708656

0.0529523

0.035039

0.0171258

Z+

Y+

-2 -1 0 1 20

0.5

TEMPERATURE

0.14093

0.13416

0.12739

0.120619

0.113849

0.107079

0.100309

0.0935391

0.086769

0.079999

0.0732289

0.0664588

0.0596887

0.0529186

0.0461485



675

a)

b)

c)

d)

Figure 8:Iso-values of mean temperature fields<T>in the plane (Y+, Z

+),Re= 2400

a): X+= 0.5;b): X

+= 1; c): X

+ = 2.5;d): X

+ = 5

Z+

Y+

-2 -1 0 1 20

0.5

TEMPERATURE

0.31228

0.292557

0.272835

0.253112

0.233389

0.213667

0.193944

0.174221

0.154499

0.134776

0.115053

0.0953308

0.0756082

0.0558855

0.0361629

Z+

Y+

-2 -1 0 1 20

0.5

1

TEMPERATURE

0.244115

0.227533

0.210951

0.194368

0.177786

0.161204

0.144621

0.128039

0.111457

0.0948743

0.078292

0.0617097

0.0451273

0.028545

0.0119627

Z+

Y+

-2 -1 0 1 20

0.5

1

TEMPERATURE

0.15801

0.147178

0.136345

0.125513

0.11468

0.103848

0.0930151

0.0821826

0.07135

0.0605175

0.0496849

0.0388524

0.0280198

0.0171873

0.00635474

Z+

Y+

-2 -1 0 1 20

0.5

1

1.5

TEMPERATURE

0.1004

0.0929762

0.0855525

0.0781287

0.0707049

0.0632811

0.0558573

0.0484335

0.0410097

0.0335859

0.0261621

0.0187384

0.0113146

0.00389077

-0.00353301



676

a)

b)

c)

d)

Figure 9: Iso-values of mean temperature fields<T>in the plane (Y+, Z

+),Re= 4800.

a): X+= 0.5;b): X

+= 1; c): X

+ = 2.5;d): X

+ = 5

III.2 Standard deviation of means temperature We obtain the temperature fluctuations shown in the previous paragraph that we

represent through the standard deviations.

The figures 10a, 10b, and 10c below represent the iso-values of the standard deviation

of mean temperatures in different positions of the plane (Y+, Z

+), for a Reynolds number of

1200. We note that the symmetry of the two jets with respect to axes 0X+

and 0Y+

is

confirmed. The standard deviation of the mean temperature decreases when the jets move

Z+

Y+

-2 -1 0 1 20

0.5

1

1.5

TEMPERATURE

0 .295613

0 .275175

0 .254737

0 .234299

0 .213861

0 .193424

0 .172986

0 .152548

0 .13211

0 .111672

0 .0912341

0 .0707962

0 .0503583

0 .0299204

0 .00948254

Z+

Y+

-2 -1 0 1 20

0.5

1

1.5

TEMPERATURE

0 .22666

0 .210599

0 .194539

0 .178478

0 .162417

0 .146356

0 .130295

0 .114234

0 .0981732

0 .0821123

0 .0660514

0 .0499906

0 .0339297

0 .0178688

0 .00180789

Z+

Y+

-2 -1 0 1 20

0.5

1

1.5

TEMPERATURE

0.159154

0.14855

0.137945

0.12734

0.116735

0.106131

0.0955258

0.084921

0.0743163

0.0637115

0.0531067

0.0425019

0.0318971

0.0212924

0.0106876

Z+

Y+

-2 -1 0 1 20

0.5

1

1.5

TEMPERATURE

0.11203

0.104573

0.097117

0.0896605

0.0822041

0.0747476

0.0672912

0.0598347

0.0523783

0.0449218

0.0374654

0.0300089

0.0225524

0.015096

0.00763954



677

away along the longitudinal axis 0X+. At the position X

+= 0.5, this iso-value is 0.04 in the

hottest zone and it become 0.01 at the position X+ = 5. The influence of longitudinal flow on

the two jets is very important.

The figures 11a, 11b, 11c and 11d below represent these standard deviations in

different positions of the plane (Y+, Z

+) for a Reynolds number of 2400. The decrease of the

standard deviation with distance along the longitudinal axis is confirmed. In the hottest zone,

it is from 0.06 at X+

= 0.5, and 0.02 at X+

= 5. The asymmetry between the two jets is

observed from the position X+

= 1.

a)

b)

c)

Figure 10: Standard deviation of mean temperature<T'

2>

1/2in the plane (Y

+, Z

+). Re= 1200.

a): X+= 0.5; b): X

+= 1; c): X

+ = 5

Z+

Y+

-2 -1 0 1 20

0.5

ECART-TYPE

0.0494505

0.0461963

0.0429421

0.0396879

0.0364337

0.0331795

0.0299252

0.026671

0.0234168

0.0201626

0.0169084

0.0136542

0.0104

0.00714577

0.00389156

Z+

Y+

-2 -1 0 1 20

0.5

ECART-TYPE

0.0358285

0.0334971

0.0311658

0.0288344

0.026503

0.0241716

0.0218403

0.0195089

0.0171775

0.0148462

0.0125148

0.0101834

0.00785206

0.00552069

0.00318932

Z+

Y+

-2 -1 0 1 20

0.5

ECART-TYPE

0.018631

0.0174407

0.0162505

0.0150602

0.0138699

0.0126796

0.0114894

0.0102991

0.00910883

0.00791856

0.00672829

0.00553802

0.00434775

0.00315748

0.00196721



678

a)

b)

c)

d)


2>

1/2in the plane (Y

+, Z

+). Re= 2400.

a): X+= 0.5; b): X

+= 1; c): X

+ = 2.5; d) X

+ = 5.

The figures 12a, 12b, 12c and 12d below represent these standard deviations in the

previous positions of the plane (Y+, Z

+) for a Reynolds number of 4800. In the hottest zone,

the standard deviation increases when the two jets move along the longitudinal axis.

In general, we note that highest standard deviation of the mean temperature

corresponds to the values of Reynolds number 2400. We saw in the previous section that this

case of Re = 2400, was one where the dispersion of passive scalar was perfect.

Z+

Y+

-2 -1 0 1 20

0.5

ECART-TYPE

0.0646835

0.0604049

0.0561262

0.0518476

0.047569

0.0432903

0.0390117

0.0347331

0.0304544

0.0261758

0.0218972

0.0176185

0.0133399

0.00906128

0.00478265

Z+

Y+

-2 -1 0 1 20

0.5

1

ECART-TYPE

0.0518896

0.0484646

0.0450396

0.0416146

0.0381896

0.0347647

0.0313397

0.0279147

0.0244897

0.0210647

0.0176398

0.0142148

0.0107898

0.00736482

0.00393984

Z+

Y+

-2 -1 0 1 20

0.5

1

ECART-TYPE

0.0336098

0.0314054

0.0292009

0.0269965

0.0247921

0.0225876

0.0203832

0.0181788

0.0159743

0.0137699

0.0115655

0.00936104

0.0071566

0.00495217

0.00274773

Z+

Y+

-2 -1 0 1 20

0.5

1

1.5

ECART-TYPE

0.0233372

0.0218155

0.0202938

0.0187721

0.0172504

0.0157287

0.014207

0.0126853

0.0111636

0.00964191

0.00812021

0.00659851

0.00507681

0.0035551

0.0020334



679

a)

b)

c)

d)


2>

1/2in the plane (Y

+, Z

+). Re= 4800.

a): X+= 0.5;b): X

+= 1;c): X

+ = 2.5; d) X

+ = 5

IV. CONCLUSIONS

The interaction between a longitudinal flow and two jets preheated has a great

influence on the passive scalar dispersion. In view of the figures shown in the previous

sections, we can say that when the two jets are issued, the scalar is transported directly

downstream from a straight line by gradually dispersing. This has already been highlighted

by Gosse [1], in the wake of Ahmed body. This dispersion is best done in the case where the

jets are less influenced by the longitudinal flow. To further explore this issue, a study of the

dynamic range must be made to understand the influence of the vortex on the dispersion of

passive scalar in the turbulent flow.

ACKNOWLEDGEMENT

The authors acknowledge the CORIA UMR 6614 CNRS University of Rouen-France,

and The University Institute of Technology of Ngaoundere, Cameroon.

Z +

Y+

-2 - 1 0 1 20

0 .5

1

1 .5

E C A R T - T Y P E

0 .0 3 6 6 7 7 1

0 .0 3 4 2 5 2 2

0 .0 3 1 8 2 7 4

0 .0 2 9 4 0 2 5

0 .0 2 6 9 7 7 7

0 .0 2 4 5 5 2 8

0 .0 2 2 1 2 8

0 .0 1 9 7 0 3 2

0 .0 1 7 2 7 8 3

0 .0 1 4 8 5 3 5

0 .0 1 2 4 2 8 6

0 .0 1 0 0 0 3 8

0 .0 0 7 5 7 8 9 6

0 .0 0 5 1 5 4 1 2

0 .0 0 2 7 2 9 2 8

Z +Y

+-2 - 1 0 1 2

0

0 .5

1

1 .5

E C A R T - T Y P E

0 .0 2 9 6 0 2 7

0 .0 2 7 6 9 2 1

0 .0 2 5 7 8 1 4

0 .0 2 3 8 7 0 8

0 .0 2 1 9 6 0 2

0 .0 2 0 0 4 9 6

0 .0 1 8 1 3 9

0 .0 1 6 2 2 8 4

0 .0 1 4 3 1 7 8

0 .0 1 2 4 0 7 2

0 .0 1 0 4 9 6 6

0 .0 0 8 5 8 5 9 9

0 .0 0 6 6 7 5 3 8

0 .0 0 4 7 6 4 7 8

0 .0 0 2 8 5 4 1 7

Z +

Y+

-2 - 1 0 1 20

0 .5

1

1 .5

E C A R T - T Y P E

0 .0 2 0 0 0 2 2

0 .0 1 8 6 8 2 8

0 .0 1 7 3 6 3 5

0 .0 1 6 0 4 4 1

0 .0 1 4 7 2 4 7

0 .0 1 3 4 0 5 3

0 .0 1 2 0 8 5 9

0 .0 1 0 7 6 6 5

0 .0 0 9 4 4 7 1 7

0 .0 0 8 1 2 7 7 8

0 .0 0 6 8 0 8 4

0 .0 0 5 4 8 9 0 2

0 .0 0 4 1 6 9 6 4

0 .0 0 2 8 5 0 2 6

0 .0 0 1 5 3 0 8 8

Z +

Y+

-2 - 1 0 1 20

0 .5

1

1 .5

E C A R T -T Y P E

0 .0 1 4 0 8 0 9

0 .0 1 3 1 7 8 2

0 .0 1 2 2 7 5 4

0 .0 1 1 3 7 2 7

0 .0 1 0 4 7

0 .0 0 9 5 6 7 2 3

0 .0 0 8 6 6 4 4 9

0 .0 0 7 7 6 1 7 6

0 .0 0 6 8 5 9 0 2

0 .0 0 5 9 5 6 2 9

0 .0 0 5 0 5 3 5 5

0 .0 0 4 1 5 0 8 2

0 .0 0 3 2 4 8 0 8

0 .0 0 2 3 4 5 3 5

0 .0 0 1 4 4 2 6 2



680

REFERENCES

[1] K. Gosse. Etude de la dissipation d’un scalaire passif en aval d’un corps d’Ahmed. Ph. D.

Thesis. University of Rouen, France, 2006.

[2] C. Kupper and F. S. Henry, Numerical simulation of flow in a circular duct fitted with air-

jet vortex generators, Int. J. Numer. Meth. Fluids, 38: 919 – 943, 2002.

[3] C. P. Tilmann, K. J. Langan, J. G. Betterton and M. J. Wilson, Characterization of pulsed

vortex generator jets for active flow control. Symposium on “Active Control Technology for

enhanced performance operational capabilities of military aircraft: Land vehicles and sea

vehicles”. RTO MP-051, 8 – 11. Germany, 2000.

[4] P. S. Kothnur and N. T. Clemens, Effects of unsteady strain rate on scalar dissipation

structures in turbulent planar jets. Physics of fluid, 17, 2005.

[5] J. Gibb and B. H. Anderson, Vortex flow control applied to aircraft intake ducts. CEAS

Europeans Forum on high lift & separation control, Bath, UK, 1995.

[6] T. P. Bray and K. P. Garry, Optimisation of jet vortex generators with respect to system

design parameters. The Aeronautical Journal, 1999.

[7] P. Paranthoën and J. C. Lecordier, Mesure de température dans les écoulements. Revue

Générale de la Thermique, 34, pp. 286 – 308. Elsevier, Paris, 1996.

[8] L. Rosset, P. Paranthoën, J. C. Lecordier and M. Gonzalez, Anisotropy of a thermal field

at dissipative scales in the case of small-case injection. Phys. Fluids., 13, 3729 – 3737, 2001.

[9] Kavitha T, Rajendran A, Durairajan A and Shanmugam A, “Heat Transfer Enhancement

Using Nano Fluids And Innovative Methods - An Overview"International Journal of

Mechanical Engineering & Technology (IJMET), Volume3, Issue2, 2012, pp. 769 - 782,

Published by IAEME.

[10] Dr P.Ravinder Reddy, Dr K.Srihari and Dr S. Raji Reddy “Combined Heat And Mass

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Volume3, Issue2, 2012, pp. 573 - 593, Published by IAEME.

NOMENCLATURE

Small letters

x = longitudinal coordinate (m)

y = vertical coordinate (m)

z = transversal coordinate (m)

d = diameter of the holes on the plate (m)

Capital letters H distance between one of the two holds from the principal axe (m)

∆Tréf Temperature difference between hot jet and the exterior (K)

T’ Temperature fluctuations (K)

Rw Hot wire resistance (Ω)

Pui Electrical power supplied (Watt)

Ui Flow velocity at the outlet of the nozzle (m.s-1

)

Uj Jet exit velocity (m.s-1

)

0x longitudinal axis

0y vertical axis



681

0z transversal axis

S The location point of the two jets sources

Greeksymbols

ν Kinetic viscosity of air (m2.s

-1)

ρ Volume mass (Kg.m-3

)

λ Thermal conductivity (J.m-2

)

No dimensional numbers Re Reynolds number

Prt Turbulent Prandtl number

Nu Nusselt number

Exponents, indices and specials characters

+ Normalized value (H for lengths) and (∆Tréf for temperatures)

<T> Mean temperature T

<X> Means time of a quantity X

<X'2>

1/2 Standard deviation of a quantity X

<X'2> Variance of a quantity X

Documents

Experimental investigation of two heated oblique