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Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows

Publication ,  Journal Article
Ma, T; Ott, B; Fröhlich, J; Bragg, AD
Published in: Journal of Fluid Mechanics
November 25, 2021

Data from direct numerical simulations of disperse bubbly flows in a vertical channel are used to study the effect of the bubbles on the carrier-phase turbulence. We developed a new method, based on an extension of the barycentric map approach, that allows us to quantify and visualize the anisotropy and componentiality of the flow at any scale. Using this we found that the bubbles significantly enhance anisotropy in the flow at all scales compared with the unladen case, and that for some bubble cases, very strong anisotropy persists down to the smallest scales of the flow. The strongest anisotropy observed was for the cases involving small bubbles. Concerning the energy transfer among the scales of the flow, our results indicate that for the bubble-laden cases, the energy transfer is from large to small scales, just as for the unladen case. However, there is evidence of an upscale transfer when considering the transfer of energy associated with particular components of the velocity field. Although the direction of the energy transfer is the same with and without the bubbles, the behaviour of the energy transfer is significantly modified by the bubbles, suggesting that the bubbles play a strong role in altering the activity of the nonlinear term in the flow. The skewness of the velocity increments also reveals a strong effect of the bubbles on the flow, changing both its sign and magnitude compared with the single-phase case. We also consider the normalized forms of the fourth-order structure functions, and the results reveal that the introduction of bubbles into the flow strongly enhances intermittency in the dissipation range, but suppresses it at larger scales. This strong enhancement of the dissipation-scale intermittency has significant implications for understanding how the bubbles might modify the mixing properties of turbulent flows.

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Published In

Journal of Fluid Mechanics

DOI

EISSN

1469-7645

ISSN

0022-1120

Publication Date

November 25, 2021

Volume

927

Related Subject Headings

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

Citation

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Ma, T., Ott, B., Fröhlich, J., & Bragg, A. D. (2021). Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows. Journal of Fluid Mechanics, 927. https://doi.org/10.1017/jfm.2021.760
Ma, T., B. Ott, J. Fröhlich, and A. D. Bragg. “Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows.” Journal of Fluid Mechanics 927 (November 25, 2021). https://doi.org/10.1017/jfm.2021.760.
Ma T, Ott B, Fröhlich J, Bragg AD. Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows. Journal of Fluid Mechanics. 2021 Nov 25;927.
Ma, T., et al. “Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows.” Journal of Fluid Mechanics, vol. 927, Nov. 2021. Scopus, doi:10.1017/jfm.2021.760.
Ma T, Ott B, Fröhlich J, Bragg AD. Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows. Journal of Fluid Mechanics. 2021 Nov 25;927.
Journal cover image

Published In

Journal of Fluid Mechanics

DOI

EISSN

1469-7645

ISSN

0022-1120

Publication Date

November 25, 2021

Volume

927

Related Subject Headings

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