# Measurements of thermally stratified pipe flow using image-processing techniques

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## 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 number*Ri* = 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## 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

*I*_{0}Intensity of an excitation beam

*I*_{c}(*T*)Calibration curve between temperature and fluorescence intensity

*I*_{ref}Reference intensity of fluorescence radiation

*Re*_{b}Reynolds number based on bulk velocity,

*U*_{ b }*D/v**Ri*Overall Richardson number based on velocity difference,

*βgDΔT/ΔU*^{2}*t*Time

*Δt*Time interval between the reference and corresponding matrix

*T*Temperature

*T*_{1},*T*_{2}Temperature of lower and upper layer

*T*^{*}Normalized temperature, (

*T−T*_{1})/*ΔT**T*_{c}(I)Inverse function of temperature as a function of

*I*_{ c }*T*_{ref}Reference temperature

*ΔT*Temperature difference between upper and lower flow,

*T*_{2}−*T*_{1}*U*_{1}Velocity of lower stream

*U*_{2}Velocity of upper stream

*U*_{b}Bulk velocity

*U*_{c}Streamwise mean velocity at

*Y*/*D*=0*ΔU*Streamwise velocity difference between upper and lower flow,

*U*_{1}−*U*_{2}*u′, v′, T′*Fluctuating component of

*U, 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

- Adrian, R. J. 1986: Multi-point optical measurements of simultaneous vectors in unsteady flow — a review. Int. J. Heat & Fluid Flow 7, 127–145Google Scholar
- Guilbault, G. G. 1973: Practical technique for measurement: theory, methods and techniques. New York, DekkerGoogle Scholar
- Jimenez, J.; Cogollos, M.; Bernal, L. P. 1985: A perspective view of the plane mixing layer. J. Fluid Mech. 152, 125–143Google Scholar
- Joklik, R. G.; Horvath, J. J.; Semerjian, H. G. 1991: Temperature measurements in flames using thermally assisted laser-induced fluorescence of Ga. Appl Opt 30: 12, 1497–1504Google Scholar
- Kobayashi, K.; Hishida, K.; Maeda, M. 1990: Turbulent transport across stable thermal stratified layer in a circular pipe. Proc. 9th Int. Heat Transfer Conf., Jerusalem/Israel, Vol 5, pp 341–346Google Scholar
- Kobayashi, K.; Sakakibara, J.; Hishida, K.; Maeda, M. 1991: Time-series measurements of turbulent flow field using image processing system, proceedings, experimental and numerical flow visualization 1991. Winter annual meeting ASME, Atlanta, pp 155–162Google Scholar
- Komori, S.; Kanzaki, T.; Murakami, Y.; Ueda, H. 1989: Simultaneous measurements of instantaneous concentration of two species using mixed in a turbulent flow by using a combined laser-induced fluorescence and laser-scattering technique. Phys. Fluids A 1, 2, 349–352Google Scholar
- Landreth, C. C.; Adrian, R. J. 1988: Impingement of a low Reynolds number turbulent circular jet onto a flat plate at normal incidence. 11th Symposium on Turbulence, Rolla, MOGoogle Scholar
- Maeda, M.; Sakakibara, J.; Hishida, K. 1992: Field measurements of velocity and temperature by digital signal processing. ICHMT Int Seminar, Imaging in Transport Processes, pp 239–248Google Scholar
- Nakajima, T.; Utsunomiya, M.; Ikeda, Y.; Matsumoto, R. 1990: Simultaneous measurement of velocity and temperature of water using LDV and fluorescence technique. 5th Int. Symp. on Appl. of LASER Tech. to Fluid Mech., Lisbon, 12.1Google Scholar
- Sakakibara, J.; Hishida, K.; Maeda, M. 1992: Simultaneous and time series measurements of two-dimensional velocity and temperature fields using an image processing technique. 6th Int. Symp. on Appl. of LASER Tech. to Fluid Mech., Lisbon, 23.5Google Scholar
- Walker, D. A. 1987: A fluorescence technique for measurement of concentration in mixing liquids. J. Phys. E. Sci. Instrum. 20: 217–224Google Scholar
- Yamamoto, F.; Dai, Y.; Koukawa, M.; Itoh, M.; Uemura, T. 1989: Numerical simulation on error analysis in particle tracking velocimeter by correlation method. Proceedings, Flow Visualization-1989, Winter annual meeting ASME, California, pp 9–14Google Scholar
- Yano, M. 1983: Velocity measurement using correlation concerning with digital tracer image, Journal of the Flow Visualization Society of Japan, Vol 3, No. 10, pp 71–74 (in Japanese)Google Scholar