Small-scale intermittency of premixed turbulent flames

Premixed turbulent flames, encountered in power generation and propulsion engines, are an archetype of a randomly advected, self-propagating surface. While such a flame is known to exhibit large-scale intermittent flapping, the possible intermittency of its small-scale fluctuations has been largely...

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Bibliographic Details
Published in:Journal of fluid mechanics 2023-02, Vol.957, Article A21
Main Authors: Roy, Amitesh, Picardo, Jason R., Emerson, Benjamin, Lieuwen, Tim C., Sujith, R.I.
Format: Article
Language:English
Subjects:
Flapping
Fluctuations
Frequency spectra
Frequency spectrum
Heat release rate
Heat transfer
Intermittency
JFM Papers
Kinematics
Phenomenology
Reynolds number
Self propagation
Turbulent flames
Velocity
Viscosity
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Summary:Premixed turbulent flames, encountered in power generation and propulsion engines, are an archetype of a randomly advected, self-propagating surface. While such a flame is known to exhibit large-scale intermittent flapping, the possible intermittency of its small-scale fluctuations has been largely disregarded. Here, we experimentally reveal the inner intermittency of a premixed turbulent V-flame, while clearly distinguishing this small-scale feature from large-scale outer intermittency. From temporal measurements of the fluctuations of the flame, we find a frequency spectrum that has a power-law subrange with an exponent close to $-2$, which is shown to follow from Kolmogorov phenomenology. Crucially, however, the moments of the temporal increment of the flame position are found to scale anomalously, with exponents that saturate at higher orders. This signature of small-scale inner intermittency is shown to originate from high-curvature, cusp-like structures on the flame surface, which have significance for modelling the heat release rate and other key properties of premixed turbulent flames.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2023.63