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Interaction of a turbulent flame with the very-large-scale structures in a channel flow.

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Title: Interaction of a turbulent flame with the very-large-scale structures in a channel flow.
Authors: Chi, Cheng1 (AUTHOR) cheng.chi@ovgu.de, Theisel, Holger2 (AUTHOR), Thévenin, Dominique1 (AUTHOR)
Source: European Journal of Mechanics B: Fluids. Sep2023, Vol. 101, p167-175. 9p.
Subjects: Channel flow, Flame, Proper orthogonal decomposition, Turbulent flow, Chemical kinetics
Abstract: Combustion processes taking place in large-scale burners may need to consider the impact of the recently identified very-large-scale motions (VLSM) appearing in wall-bounded turbulent flows. While VLSM in non-reacting, cold flows have been found to be important and noticeably impact turbulence statistics, the possible influence of VLSM on turbulent premixed flames has not been considered up to now to the best of our knowledge. The present study investigates the interaction of a turbulent flame with VLSM in a channel flow using direct numerical simulations (DNS). Detailed chemical kinetics have been used to compute a H 2 flame. The turbulent channel flow corresponds to Re τ = 280, while the premixed flame is associated to a Damköhler number Da = 0.167. First, VLSM have been identified for the non-reacting flow by proper orthogonal decomposition (POD). Interestingly, the propagation of the turbulent flame is found to have a negligible effect on the VLSM, highlighting their resilience. At the same time, the VLSM do not modulate strongly the flame structure, while it is noticeably affected by small-scale vortices. This decoupling might be explained by the very different length scales of both processes, the VLSM covering the full channel length, while the turbulent flame is characterized by small-scale structures. In the same manner, the characteristic time scales also differ widely, the flame time scale being much faster than the characteristic time of the VLSM. The flame curvature is positively correlated with the fluctuating streamwise velocity when the flame is still far from the wall. When approaching the wall, flame quenching takes place in a complex process. Overall, it appears for the present conditions that VLSM do not impact directly the turbulent flame propagation, but there is still an indirect impact through the modifications of the turbulence statistics. [ABSTRACT FROM AUTHOR]
Copyright of European Journal of Mechanics B: Fluids is the property of Elsevier B.V. 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: 169334372
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
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  Label: Title
  Group: Ti
  Data: Interaction of a turbulent flame with the very-large-scale structures in a channel flow.
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  Data: <searchLink fieldCode="AR" term="%22Chi%2C+Cheng%22">Chi, Cheng</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> cheng.chi@ovgu.de</i><br /><searchLink fieldCode="AR" term="%22Theisel%2C+Holger%22">Theisel, Holger</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Thévenin%2C+Dominique%22">Thévenin, Dominique</searchLink><relatesTo>1</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22European+Journal+of+Mechanics+B%3A+Fluids%22">European Journal of Mechanics B: Fluids</searchLink>. Sep2023, Vol. 101, p167-175. 9p.
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  Data: <searchLink fieldCode="DE" term="%22Channel+flow%22">Channel flow</searchLink><br /><searchLink fieldCode="DE" term="%22Flame%22">Flame</searchLink><br /><searchLink fieldCode="DE" term="%22Proper+orthogonal+decomposition%22">Proper orthogonal decomposition</searchLink><br /><searchLink fieldCode="DE" term="%22Turbulent+flow%22">Turbulent flow</searchLink><br /><searchLink fieldCode="DE" term="%22Chemical+kinetics%22">Chemical kinetics</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Combustion processes taking place in large-scale burners may need to consider the impact of the recently identified very-large-scale motions (VLSM) appearing in wall-bounded turbulent flows. While VLSM in non-reacting, cold flows have been found to be important and noticeably impact turbulence statistics, the possible influence of VLSM on turbulent premixed flames has not been considered up to now to the best of our knowledge. The present study investigates the interaction of a turbulent flame with VLSM in a channel flow using direct numerical simulations (DNS). Detailed chemical kinetics have been used to compute a H 2 flame. The turbulent channel flow corresponds to Re τ = 280, while the premixed flame is associated to a Damköhler number Da = 0.167. First, VLSM have been identified for the non-reacting flow by proper orthogonal decomposition (POD). Interestingly, the propagation of the turbulent flame is found to have a negligible effect on the VLSM, highlighting their resilience. At the same time, the VLSM do not modulate strongly the flame structure, while it is noticeably affected by small-scale vortices. This decoupling might be explained by the very different length scales of both processes, the VLSM covering the full channel length, while the turbulent flame is characterized by small-scale structures. In the same manner, the characteristic time scales also differ widely, the flame time scale being much faster than the characteristic time of the VLSM. The flame curvature is positively correlated with the fluctuating streamwise velocity when the flame is still far from the wall. When approaching the wall, flame quenching takes place in a complex process. Overall, it appears for the present conditions that VLSM do not impact directly the turbulent flame propagation, but there is still an indirect impact through the modifications of the turbulence statistics. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of European Journal of Mechanics B: Fluids is the property of Elsevier B.V. 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:
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      – Type: doi
        Value: 10.1016/j.euromechflu.2023.05.008
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 9
        StartPage: 167
    Subjects:
      – SubjectFull: Channel flow
        Type: general
      – SubjectFull: Flame
        Type: general
      – SubjectFull: Proper orthogonal decomposition
        Type: general
      – SubjectFull: Turbulent flow
        Type: general
      – SubjectFull: Chemical kinetics
        Type: general
    Titles:
      – TitleFull: Interaction of a turbulent flame with the very-large-scale structures in a channel flow.
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            NameFull: Chi, Cheng
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            NameFull: Theisel, Holger
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            NameFull: Thévenin, Dominique
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          Dates:
            – D: 01
              M: 09
              Text: Sep2023
              Type: published
              Y: 2023
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              Value: 101
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            – TitleFull: European Journal of Mechanics B: Fluids
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