Comparison of near wake-flow structure behind a solid cap with an attached bubble and a solid counterpart

Akira T. Tokuhiro, Hidekazu No, Michel Call, Koichi Hishida

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

An experiment to study the near-wake flow structure behind an air bubble attached to a cap and separately, a solid equivalent was conducted. The objective was to elucidate the near-wake characteristics of the "cap-bubble" relative to the solid; in particular, to elucidate the role of the "moving tail". Experiments were performed in 80 × 80 mm2 × 1 m tall channel with each object suspended in downward flow of water. Both the cap-bubble and solid had an approximate equivalent diameter, Deq ∼ 11.5 mm (volume ∼ 0.8 mL), The average downward flow velocity (U ∼ 25 cm/s ∼ rise velocity of bubble) defined Reynolds number was, 2 450 < ReDcq <2 890. The Eötvös and Weber numbers were, 17.8 < Eö < 17.85, 6.04 < We <6.06. Particle Image. Velocimetry using a cross-correlation method was used to generate velocity data; vorticity, turbulent kinetic energy (TKE) and other parameters we then calculated. Graphic and numerical comparisons between the objects led to the following: 1) for the cap-bubble, the influence on the flow structure due to motion of the tail is relatively minor, 2) tail motion contributes to transverse fluctuations and uniformity in TKE distribution and 3) object deformation, oscillation and gyration localizes the flow structure in contrast to a solid object. Results are discussed.

Original languageEnglish
Pages (from-to)737-747
Number of pages11
JournalJSME International Journal, Series B: Fluids and Thermal Engineering
Volume49
Issue number3
DOIs
Publication statusPublished - 2006 Dec 1

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Keywords

  • Bubble
  • Bubble motion
  • Flow structure
  • Near-wake
  • Particle image velocimetry

ASJC Scopus subject areas

  • Mechanical Engineering
  • Physical and Theoretical Chemistry
  • Fluid Flow and Transfer Processes

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