Turbulent flow past a bubble and an ellipsoid using shadow-image and PIV techniques

A. Tokuhiro, M. Maekawa, K. Iizuka, K. Hishida, M. Maeda

Research output: Contribution to journalArticle

91 Citations (Scopus)

Abstract

An experimental investigation on flow around an oscillating bubble and solid ellipsoid with a flat bottom was conducted. A single air bubble (equivalent diameter D(e) = 9.12 mm) was attached to a small disk (~1 mm) at the end of a needle and suspended across a vertical square channel (100 mm) by wire wherein water flowed downward at a constant flowrate. The solid ellipsoid (D(e) ~ 9.1 mm) was suspended across the square channel in the same manner. The equivalent diameter-based Reynolds and Eotvos number range, 1950 < Re < 2250 and 11 < Eo < 11.5, placed the bubble in the 'wobbly' regime while the flow in its wake was turbulent. A constant flowrate and one bubble size was used such that flow in the wake was turbulent. Velocity measurements of the flow field around the bubble or solid were made using a one CCD camera Digital Particle Image Velocimetry (DPIV) system enhanced by Laser Induced Fluorescence (LIF). The shape of the bubble or solid was simultaneously recorded along with the velocity using a second CCD camera and an Infrared Shadow Technique (IST). In this way both the flow-field and the boundary of the bubble (solid) were measured. The velocity vector plots of flow around and in the wake of a bubble/solid, supplemented by profiles and contours of the average and root-mean-square velocities, vorticity, Reynolds stress and turbulent kinetic energy, revealed differences in the wake flow structure behind a bubble and solid. One of the significant differences was in the inherent, oscillatory motion of the bubble which not only produced vorticity in the near-wake, but as a result of apparent vorticity stretching distributed the turbulent kinetic energy associated with this flow more uniformly on its wake, in contrast to the solid.

Original languageEnglish
Pages (from-to)1383-1406
Number of pages24
JournalInternational Journal of Multiphase Flow
Volume24
Issue number8
DOIs
Publication statusPublished - 1998 Dec 1

Keywords

  • Bubble oscillations
  • Digital particle image velocimetry (DPIV)
  • Infrared shadow technique (IST)
  • Laser induced fluorescence (LIF)
  • Single-bubble
  • Turbulent wake flow

ASJC Scopus subject areas

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

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