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Turbulent Rayleigh–Bénard convection with bubbles attached to the plate.

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Title: Turbulent Rayleigh–Bénard convection with bubbles attached to the plate.
Authors: Liu, Hao-Ran1 (AUTHOR), Chong, Kai Leong2 (AUTHOR), Yang, Rui1 (AUTHOR), Verzicco, Roberto1,3,4 (AUTHOR), Lohse, Detlef1,5 (AUTHOR) d.lohse@utwente.nl
Source: Journal of Fluid Mechanics. 8/25/2022, Vol. 945, p1-12. 12p.
Subjects: Rayleigh-Bénard convection, Thermal boundary layer, Nusselt number, Rayleigh number, Mass transfer, Boundary layer (Aerodynamics), Prandtl number, Bubbles
Abstract: We numerically investigate turbulent Rayleigh–Bénard convection with gas bubbles attached to the hot plate, mimicking a core feature in electrolysis, catalysis or boiling. The existence of bubbles on the plate reduces the global heat transfer due to the much lower thermal conductivity of gases as compared with liquids and changes the structure of the boundary layers. The numerical simulations are performed in three dimensions at Prandtl number $\mbox{Pr}=4.38$ (water) and Rayleigh number $10^7\leqslant \mbox{Ra}\leqslant 10^8$. For simplicity, we assume the bubbles to be equally sized and having pinned contact lines. We vary the total gas-covered area fraction $0.18 \leqslant S_0 \leqslant 0.62$ , the relative bubble height $0.02\leqslant h/H \leqslant 0.05$ (where $H$ is the height of the Rayleigh–Bénard cell), the bubble number $40 \leqslant n \leqslant 144$ and their spatial distribution. In all cases, asymmetric temperature profiles are observed, which we quantitatively explain based on the heat flux conservation at each horizontal section. We further propose the idea of using an equivalent single-phase set-up to mimic the system with attached bubbles. Based on this equivalence, we can calculate the heat transfer. Without introducing any free parameter, the predictions for the Nusselt number, the upper and lower thermal boundary layer thicknesses and the mean centre temperature agree well with the numerical results. Finally, our predictions also work for the cases with much larger $\mbox{Pr}$ (e.g. $400$), which indicates that our results can also be applied to predict the mass transfer in water electrolysis with bubbles attached to the electrode surface or in catalysis. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Fluid Mechanics is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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Header DbId: egs
DbLabel: Engineering Source
An: 159190989
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 0
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  Label: Title
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  Data: Turbulent Rayleigh–Bénard convection with bubbles attached to the plate.
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  Data: <searchLink fieldCode="AR" term="%22Liu%2C+Hao-Ran%22">Liu, Hao-Ran</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Chong%2C+Kai+Leong%22">Chong, Kai Leong</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Yang%2C+Rui%22">Yang, Rui</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Verzicco%2C+Roberto%22">Verzicco, Roberto</searchLink><relatesTo>1,3,4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lohse%2C+Detlef%22">Lohse, Detlef</searchLink><relatesTo>1,5</relatesTo> (AUTHOR)<i> d.lohse@utwente.nl</i>
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Fluid+Mechanics%22">Journal of Fluid Mechanics</searchLink>. 8/25/2022, Vol. 945, p1-12. 12p.
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  Data: <searchLink fieldCode="DE" term="%22Rayleigh-Bénard+convection%22">Rayleigh-Bénard convection</searchLink><br /><searchLink fieldCode="DE" term="%22Thermal+boundary+layer%22">Thermal boundary layer</searchLink><br /><searchLink fieldCode="DE" term="%22Nusselt+number%22">Nusselt number</searchLink><br /><searchLink fieldCode="DE" term="%22Rayleigh+number%22">Rayleigh number</searchLink><br /><searchLink fieldCode="DE" term="%22Mass+transfer%22">Mass transfer</searchLink><br /><searchLink fieldCode="DE" term="%22Boundary+layer+%28Aerodynamics%29%22">Boundary layer (Aerodynamics)</searchLink><br /><searchLink fieldCode="DE" term="%22Prandtl+number%22">Prandtl number</searchLink><br /><searchLink fieldCode="DE" term="%22Bubbles%22">Bubbles</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: We numerically investigate turbulent Rayleigh–Bénard convection with gas bubbles attached to the hot plate, mimicking a core feature in electrolysis, catalysis or boiling. The existence of bubbles on the plate reduces the global heat transfer due to the much lower thermal conductivity of gases as compared with liquids and changes the structure of the boundary layers. The numerical simulations are performed in three dimensions at Prandtl number $\mbox{Pr}=4.38$ (water) and Rayleigh number $10^7\leqslant \mbox{Ra}\leqslant 10^8$. For simplicity, we assume the bubbles to be equally sized and having pinned contact lines. We vary the total gas-covered area fraction $0.18 \leqslant S_0 \leqslant 0.62$ , the relative bubble height $0.02\leqslant h/H \leqslant 0.05$ (where $H$ is the height of the Rayleigh–Bénard cell), the bubble number $40 \leqslant n \leqslant 144$ and their spatial distribution. In all cases, asymmetric temperature profiles are observed, which we quantitatively explain based on the heat flux conservation at each horizontal section. We further propose the idea of using an equivalent single-phase set-up to mimic the system with attached bubbles. Based on this equivalence, we can calculate the heat transfer. Without introducing any free parameter, the predictions for the Nusselt number, the upper and lower thermal boundary layer thicknesses and the mean centre temperature agree well with the numerical results. Finally, our predictions also work for the cases with much larger $\mbox{Pr}$ (e.g. $400$), which indicates that our results can also be applied to predict the mass transfer in water electrolysis with bubbles attached to the electrode surface or in catalysis. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Fluid Mechanics is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1017/jfm.2022.573
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 12
        StartPage: 1
    Subjects:
      – SubjectFull: Rayleigh-Bénard convection
        Type: general
      – SubjectFull: Thermal boundary layer
        Type: general
      – SubjectFull: Nusselt number
        Type: general
      – SubjectFull: Rayleigh number
        Type: general
      – SubjectFull: Mass transfer
        Type: general
      – SubjectFull: Boundary layer (Aerodynamics)
        Type: general
      – SubjectFull: Prandtl number
        Type: general
      – SubjectFull: Bubbles
        Type: general
    Titles:
      – TitleFull: Turbulent Rayleigh–Bénard convection with bubbles attached to the plate.
        Type: main
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          Name:
            NameFull: Liu, Hao-Ran
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            NameFull: Chong, Kai Leong
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            NameFull: Yang, Rui
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            NameFull: Verzicco, Roberto
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            NameFull: Lohse, Detlef
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          Dates:
            – D: 25
              M: 08
              Text: 8/25/2022
              Type: published
              Y: 2022
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            – Type: issn-print
              Value: 00221120
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            – Type: volume
              Value: 945
          Titles:
            – TitleFull: Journal of Fluid Mechanics
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