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Experiments in Fluids

, Volume 16, Issue 2, pp 82–96 | Cite as

Measurements of thermally stratified pipe flow using image-processing techniques

  • J. Sakakibara
  • K. Hishida
  • M. Maeda
Originals

Abstract

The cross-correlation technique and Laser Induced Fluorescence (LIF) have been adopted to measure the time-dependent and two-dimensional velocity and temperature fields of a stably thermal-stratified pipe flow. One thousand instantaneous and simultaneous velocity and temperature maps were obtained at overall Richardson numberRi = 0 and 2.5, from which two-dimensional vorticity, Reynolds stress and turbulent heat flux vector were evaluated. The quasi-periodic inclined vortices (which connected to the ‘crest’) were revealed from successive instantaneous maps and temporal variation of vorticity and temperature. It has been recognized that these vortices are associated with the ‘crest’ and ‘valley’ in the roll-up motion.

Keywords

Vortex Heat Flux Vorticity Crest Reynolds Stress 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

A

Fraction of the available light collected

C

Concentration of fluorescence

D

Pipe diameter

I

Fluorescence intensity

L

Sampling length along the incident beam

I0

Intensity of an excitation beam

Ic(T)

Calibration curve between temperature and fluorescence intensity

Iref

Reference intensity of fluorescence radiation

Reb

Reynolds number based on bulk velocity,U b D/v

Ri

Overall Richardson number based on velocity difference,βgDΔT/ΔU2

t

Time

Δt

Time interval between the reference and corresponding matrix

T

Temperature

T1,T2

Temperature of lower and upper layer

T*

Normalized temperature, (T−T1)/ΔT

Tc(I)

Inverse function of temperature as a function ofI c

Tref

Reference temperature

ΔT

Temperature difference between upper and lower flow,T2T1

U1

Velocity of lower stream

U2

Velocity of upper stream

Ub

Bulk velocity

Uc

Streamwise mean velocity atY/D=0

ΔU

Streamwise velocity difference between upper and lower flow,U1U2

u′, v′, T′

Fluctuating component ofU, V, T

U, V

Velocity component of X, Y direction

X

Streamwise distance from the splitter plate

Y

Transverse distance from the centerline of the pipe

Z

Spanwise distance from the centerline of the pipe

φ

Quantum yield

ɛ

Absorptivity

ω

vorticity calculated from a circulation

ν

Kinematic viscosity

Γ

circulation

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References

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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • J. Sakakibara
    • 1
  • K. Hishida
    • 1
  • M. Maeda
    • 1
  1. 1.Department of Mechanical EngineeringKeio UniversityYokohamaJapan

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