Upward and downward inclination oil-water flows

J. Y.L. Lum, T. Al-Wahaibi, P. Angeli*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

93 Citations (Scopus)


The effect of upward (+5°, +10°) and downward (-5°) pipe inclinations on the flow patterns, hold up and pressure gradient during two-liquid phase flows was investigated experimentally for mixture velocities between 0.7 and 2.5 m/s and phase fractions between 10% and 90%. The investigations were performed in a 38 mm ID stainless steel test pipe with water and oil as test fluids. High-speed video recording and local impedance and conductivity probes were used to precisely identify the different flow patterns. In both positive and negative inclinations the dispersed oil-in-water regime extended to lower mixture velocities and higher oil fractions compared to horizontal flow. A new flow pattern, oil plug flow, appeared at both +5° and +10° inclination while the stratified wavy pattern disappeared at -5° inclination. The oil to water velocity ratio was higher for the upward than for the downward flows but in the majority of cases and all inclinations oil was flowing faster than water. At low mixture velocities the velocity ratio increased with oil fraction while it decreased at high velocities. The increase became more significant as the degree of inclination increased. The frictional pressure gradient in both upward and downward flows was in general lower than in horizontal flows while a minimum occurred at all inclinations at high mixture velocities during the transition from dispersed water-in-oil to dual continuous flow.

Original languageEnglish
Pages (from-to)413-435
Number of pages23
JournalInternational Journal of Multiphase Flow
Issue number4
Publication statusPublished - Apr 2006


  • Downward flow
  • Hold up
  • Liquid-liquid flow
  • Phase distribution
  • Pressure gradient
  • Upward flow

ASJC Scopus subject areas

  • Mechanical Engineering
  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes


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