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An experimental study on the multiscale properties of turbulence in bubble-laden flows

Publication ,  Journal Article
Ma, T; Hessenkemper, H; Lucas, D; Bragg, AD
Published in: Journal of Fluid Mechanics
April 10, 2022

The properties of bubble-laden turbulent flows at different scales are investigated experimentally, focusing on the flow kinetic energy, energy transfer and extreme events. The experiments employed particle shadow velocimetry measurements to measure the flow in a column generated by a homogeneous bubble swarm rising in water, for two different bubble diameters (mm and mm) and moderate gas volume fractions . The two velocity components were measured at high resolution, and used to construct structure functions up to twelfth order for separations spanning the small to large scales in the flow. Concerning the flow anisotropy, the velocity structure functions are found to differ for separations in the vertical and horizontal directions of the flow, and the cases with smaller bubbles are the most anisotropic, with a dependence on void fraction. The degree of anisotropy is shown to increase as the order of the structure functions is increased, showing that extreme events in the flow are the most anisotropic. Our results show that the average energy transfer with the horizontal velocity component is downscale, just as for the three-dimensional single-phase turbulence. However, the energy transfer associated with the vertical component of the fluid velocity is upscale. The probability density functions of the velocity increments reveal that extreme values become more probable with decreasing Reynolds number, the opposite of the behaviour in single-phase turbulence. We visualize those extreme events and find that regions of intense small-scale velocity increments occur near the turbulent/non-turbulent interface at the boundary of the bubble wake.

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Published In

Journal of Fluid Mechanics

DOI

EISSN

1469-7645

ISSN

0022-1120

Publication Date

April 10, 2022

Volume

936

Related Subject Headings

  • Fluids & Plasmas
  • 49 Mathematical sciences
  • 40 Engineering
  • 09 Engineering
  • 01 Mathematical Sciences
 

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Ma, T., Hessenkemper, H., Lucas, D., & Bragg, A. D. (2022). An experimental study on the multiscale properties of turbulence in bubble-laden flows. Journal of Fluid Mechanics, 936. https://doi.org/10.1017/jfm.2022.86
Ma, T., H. Hessenkemper, D. Lucas, and A. D. Bragg. “An experimental study on the multiscale properties of turbulence in bubble-laden flows.” Journal of Fluid Mechanics 936 (April 10, 2022). https://doi.org/10.1017/jfm.2022.86.
Ma T, Hessenkemper H, Lucas D, Bragg AD. An experimental study on the multiscale properties of turbulence in bubble-laden flows. Journal of Fluid Mechanics. 2022 Apr 10;936.
Ma, T., et al. “An experimental study on the multiscale properties of turbulence in bubble-laden flows.” Journal of Fluid Mechanics, vol. 936, Apr. 2022. Scopus, doi:10.1017/jfm.2022.86.
Ma T, Hessenkemper H, Lucas D, Bragg AD. An experimental study on the multiscale properties of turbulence in bubble-laden flows. Journal of Fluid Mechanics. 2022 Apr 10;936.
Journal cover image

Published In

Journal of Fluid Mechanics

DOI

EISSN

1469-7645

ISSN

0022-1120

Publication Date

April 10, 2022

Volume

936

Related Subject Headings

  • Fluids & Plasmas
  • 49 Mathematical sciences
  • 40 Engineering
  • 09 Engineering
  • 01 Mathematical Sciences