Clarification of Ejection and Sweep in Rectangular Channel Turbulent Flow

Clarification of Ejection and Sweep in Rectangular Channel Turbulent Flow

Muhammad Kunta Biddinika, Noriyuki Watanabe, Masanori Aritomi, Hiroshige Kikura

(Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology)

ICONE-18Xi’ain, China, May 17-21, 2010

2

Research Laboratory for Nuclear Reactor, Tokyo Institute of TechnologyMuhammad Kunta Biddinika

ICONE-18Xi’an, China, May 17-21, 2010

Background• The flow of liquid over a solid surface gives rise to what is

known as a boundary layer. This is caused by the liquid sticking to the surface, being slowed to a stop in contact with the surface.

• As moving away from the surface, the liquid moves faster and faster until it reaches its maximum (freestream) velocity.

• Boundary layers come in two types– Laminar boundary layer : liquid at any given point in the layer is

moving in the main flow direction

– Turbulent boundary layer : more chaotic and small Eddies swirl the liquid up from the wall surface away to the edge of the boundary layer, and vice versa.

Background• Turbulent boundary layer : more chaotic and small Eddies

swirl the liquid up from the wall surface away to the edge of the boundary layer, and vice versa

3



http://www.soton.ac.uk/ses/outreach/greenpower/boundarylayers.html

Boundary Layer

wall surface

SweepEjection

Laminar Turbulent

Free streamvelocity velocity

4



Previous Study• Definition on Sweep and Ejection (Willmarth and Lu, 1972) by

using hot-wire probes

• Sweep and ejection of atmospheric turbulence quantities studied in the real maize crop canopy by using hot-wire anemometer (Jacobs et al, 2001)

• Flow structure of sweep and ejection near canopy top, studied by using particle image velocimetry (PIV) (Zhu et al, 2006, 2007).

• Study on sweep and ejection using optical method and probe method

We focused on …

(1) Optically Opaque (2) Non-Invasive

(3) Low cost(4) Simpler to use

Ultrasonic technique

Measurement techniquesOptical method

LDV, PTV, PIV

Probe method Thermal probe, electrical probe,

Complex system, high cost, optical window

contact measurement, intrude the flow

Zhu et al (2006, 2007)

Willmarth and Lu (1972), Jacobs et al (2001)

5



prob

abili

ty

ejectionsweep

• by using the measurement method, instantaneous velocity recorded

u

v

velo

city

prob

abili

ty

prob

abili

ty

t

v’

t

v’

6

t

u’ center flow

ejection

sweep



Ejection and SweepCoherent Structure in turbulent flow

A.N. Ziaeli et al, 2005

• sweep and ejection can be characterized by four quadrant events (Ziaeli et al, 2005) of the combination of the velocity fluctuation (u’ and v’)•Sweep and ejection can also be characterized by statistical method using skewness and flatness parameters

ejectionsweep

u

v

(II)f(u’)<0 f(v’)>0ejection

(I)f(u’)>0 f(v’)<0 outward

interaction

(III)f(u’)<0 f(v’)<0Inward

interaction

(IV)f(u’)>0 f(v’)<0sweep

Phenomena classification by frequency of instantaneous velocity

7



PDf

velocity

PDf

flow flow

sweep ejection

u

v

8

v’v’



Measurement challenges

position

delay time

extrapolation

gradient ≡ average velocity position

delay time

extrapolation

local gradient ≡ instantaneous velocity

UVP

9



Objective of current research in Sweep and Ejection

• To clarify whether UVP can detect sweep and ejection events or not– Considering # of pulse repetition of UVP in

obtaining instantaneous velocity

10



Experimental Apparatus

• Water circulation system

• Air supply system• Test section• Temperature

control section• Measurement

systems

Rectangular Channel Plexiglas

Length 1500mm

hydraulic equivalent diameter 33.33mm

Thickness (at meas. point) 5mm(1mm)

Working fluid Water,Air

Temperature 20±1℃Meas. point 1250mm

1

3

45

67

8

2

13

9

10

11

12

14

15

1. Overflow tank2. Pressure tap3. Test section4. Pressure sensor5. Oscilloscope6. UVP monitor7. US transducer8. Compressor9. Storage tank10.Air water mixer11.Float flowmeter12.Orifice flowmeter13.PC14.Sub-cooling system15.Centrifugal pump

• An experimental apparatus for two-directional velocity component has been prepared. The apparatus can apply the installment of 8Mhz TDX in 45° of upward and 45° of downward flow direction

• Channel dimension area is 20 mm x 100 mm and channel length is 1500 mm

• Ultrasonic TDX is installed on 1250 mm of height

• 5,000 instantaneous velocity profiles are recorded for every measuring angle line.

Measurement and calculation method

1250 mm

1500 mm

*not scalable figure



• From one of measurement point in the near-the-wall region, statistical analysis is applied in order to investigate coherent structure in turbulence

• H/2D = 62.5

• Re = 4177

experiment conditions• Near-the-wall region usually in the region of y+ ≤ 10 as

described by Lagraa et al (2004), Nakayama et al (2004),

• Which region the experiment was conducted?

13

100 101 1020

5

10

15

20

Re = 4177

y+

u+

viscous sublayer buffer layer

fully turbulent

measurement window position



• In order to obtain two-directional velocity components, it is common to perform two measurements.

is the velocity component along the angle from the axis of channel

ϑUϑ

ϑ−U is the velocity component along the angle ϑ−

°−= 90θϑ

ϑϑϑ +++ += uUU

ϑϑϑ −−− += uUUϑ+U ϑ−U are the average velocity along the the

angle ϑ+ ϑ−

ϑ+u ϑ−u are the fluctuating velocity along the the angle ϑ+ ϑ−

(1)

(2)

Measurement and calculation method



15

Results

A B

# = 8

BRe =4000

# = 32

A

# = 8

# = 32

# = 256 # = 256

v-component of velocity



0 100 200 300 400

0.1

0.2

velocity (mm/s)

pdf

0 100 200 300 400

0.1

0.2

0.3

0.4

0.5

velocity (mm/s)

pdf

0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

0 100 200 300 400

0.05

0.1

0.15

velocity (mm/s)pd

f

0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

16

Results

# = 8

BRe =4000

# = 32

A

# = 8

# = 32

# = 256 # = 256

u-component of velocity



0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

0 100 200 300 4000

0.1

0.2

velocity (mm/s)

pdf

0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

0 100 200 300 4000

0.05

0.1

0.15

velocity (mm/s)

pdf

A B

Conclusions

• For sweep and ejection investigation, near-wall region adjacent to TDX better than near-wall region in the opposite to TDX

• Large number of repetition of ultrasound pulse is better than small number repetition for investigation of sweep and ejection phenomena

• However, more experiment data is required in order to conclude whether UVP can be used for sweep and ejection study

• As suggested by previous study, the other measurement methods than the UVP method should also be applied in order to observe the sweep and ejection phenomena

17



Future Work• The current experiment results basically can not

distinguish sweep or ejection from v-component of velocity, the identification of ejection is needed to know the relation between mean velocity (u-direction) of the flow and ejection velocity (v-direction).

18



19



Thank you ..

20



Boundary Layer

Free stream

Laminar

Boundary Layer

wall surface

SweepEjection

Laminar Turbulent

Free streamvelocity velocity

21



Clarification of Ejection and Sweep in Rectangular Channel Turbulent Flow

Documents

Transcript of Clarification of Ejection and Sweep in Rectangular Channel Turbulent Flow