Turbulence structure of bubbly upward pipe flow (high spatial and temporal resolution measurements using high speed time series PTV)

Masamitsu Koyasu, Tomohiko Tanaka, Yohei Sato, Koichi Hishida

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Abstract Turbulence modification by dispersed bubbles in an upward pipe flow was investigated by particle tracking velocimetry and bubble shape projection imaging. Time duration of CMOS camera frames was much smaller than the Kolmogorov time scale, so that measurments with a high time resolution were achieved to resolve the dissipation process of turbulence in the presence of bubbles. Two different bubble diameters at the void fraction up to 1.5% were examined. The profiles of mean streamwise velocity of water were flattened in the pipe middle region, because the bubbles accumulating near the pipe wall accelerated the fluid. The flattened mean flow profiles suppressed the shearinduced turbulence intensities. The dissipative eddies around small bubbles, whose size is approximately five times the mean diameter of small bubbles, increased the dissipation rate of turbulence kinetic energy. On the other hand, the turbulence intensities were augmented by the interactions between the eddies generated by the large bubble and the shear-induced turbulence amongst large bubbles, which resulted in the significant enhancement of dissipation process of turbulence kinetic energy.

Original languageEnglish
Pages (from-to)1446-1453
Number of pages8
JournalNihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
Volume75
Issue number755
Publication statusPublished - 2009 Jul

Fingerprint

pipe flow
Pipe flow
temporal resolution
Time series
Turbulence
bubbles
spatial resolution
turbulence
high speed
high resolution
Bubbles (in fluids)
Kinetic energy
dissipation
Pipe
kinetic energy
Void fraction
vortices
Velocity measurement
profiles
Cameras

Keywords

  • Correction method
  • Multiphase flow
  • PTV
  • Turbulence energy spectra
  • Turbulence modification

ASJC Scopus subject areas

  • Mechanical Engineering
  • Condensed Matter Physics

Cite this

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abstract = "Abstract Turbulence modification by dispersed bubbles in an upward pipe flow was investigated by particle tracking velocimetry and bubble shape projection imaging. Time duration of CMOS camera frames was much smaller than the Kolmogorov time scale, so that measurments with a high time resolution were achieved to resolve the dissipation process of turbulence in the presence of bubbles. Two different bubble diameters at the void fraction up to 1.5{\%} were examined. The profiles of mean streamwise velocity of water were flattened in the pipe middle region, because the bubbles accumulating near the pipe wall accelerated the fluid. The flattened mean flow profiles suppressed the shearinduced turbulence intensities. The dissipative eddies around small bubbles, whose size is approximately five times the mean diameter of small bubbles, increased the dissipation rate of turbulence kinetic energy. On the other hand, the turbulence intensities were augmented by the interactions between the eddies generated by the large bubble and the shear-induced turbulence amongst large bubbles, which resulted in the significant enhancement of dissipation process of turbulence kinetic energy.",
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T1 - Turbulence structure of bubbly upward pipe flow (high spatial and temporal resolution measurements using high speed time series PTV)

AU - Koyasu, Masamitsu

AU - Tanaka, Tomohiko

AU - Sato, Yohei

AU - Hishida, Koichi

PY - 2009/7

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N2 - Abstract Turbulence modification by dispersed bubbles in an upward pipe flow was investigated by particle tracking velocimetry and bubble shape projection imaging. Time duration of CMOS camera frames was much smaller than the Kolmogorov time scale, so that measurments with a high time resolution were achieved to resolve the dissipation process of turbulence in the presence of bubbles. Two different bubble diameters at the void fraction up to 1.5% were examined. The profiles of mean streamwise velocity of water were flattened in the pipe middle region, because the bubbles accumulating near the pipe wall accelerated the fluid. The flattened mean flow profiles suppressed the shearinduced turbulence intensities. The dissipative eddies around small bubbles, whose size is approximately five times the mean diameter of small bubbles, increased the dissipation rate of turbulence kinetic energy. On the other hand, the turbulence intensities were augmented by the interactions between the eddies generated by the large bubble and the shear-induced turbulence amongst large bubbles, which resulted in the significant enhancement of dissipation process of turbulence kinetic energy.

AB - Abstract Turbulence modification by dispersed bubbles in an upward pipe flow was investigated by particle tracking velocimetry and bubble shape projection imaging. Time duration of CMOS camera frames was much smaller than the Kolmogorov time scale, so that measurments with a high time resolution were achieved to resolve the dissipation process of turbulence in the presence of bubbles. Two different bubble diameters at the void fraction up to 1.5% were examined. The profiles of mean streamwise velocity of water were flattened in the pipe middle region, because the bubbles accumulating near the pipe wall accelerated the fluid. The flattened mean flow profiles suppressed the shearinduced turbulence intensities. The dissipative eddies around small bubbles, whose size is approximately five times the mean diameter of small bubbles, increased the dissipation rate of turbulence kinetic energy. On the other hand, the turbulence intensities were augmented by the interactions between the eddies generated by the large bubble and the shear-induced turbulence amongst large bubbles, which resulted in the significant enhancement of dissipation process of turbulence kinetic energy.

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KW - Multiphase flow

KW - PTV

KW - Turbulence energy spectra

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