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A DNS Study of Sensitivity of Scaling Exponents for Premixed Turbulent Consumption Velocity to Transient Effects

Yu, Rixin LU and Lipatnikov, Andrei N. (2019) In Flow, Turbulence and Combustion 102(3). p.679-698
Abstract

3D Direct Numerical Simulations of propagation of a single-reaction wave in forced, statistically stationary, homogeneous, isotropic, and constant-density turbulence, which is not affected by the wave, are performed in order to investigate the influence of the wave development on scaling (power) exponents for the turbulent consumption velocity UT as a function of the rms turbulent velocity u, laminar wave speed SL, and a ratio L11F of the longitudinal turbulence length scale L11 to the laminar wave thickness δF. Fifteen cases characterized by u/SL = 0.5,1.0,2.0,5.0, or 10.0 and L11F = 2.1, 3.7, or 6.7 are... (More)

3D Direct Numerical Simulations of propagation of a single-reaction wave in forced, statistically stationary, homogeneous, isotropic, and constant-density turbulence, which is not affected by the wave, are performed in order to investigate the influence of the wave development on scaling (power) exponents for the turbulent consumption velocity UT as a function of the rms turbulent velocity u, laminar wave speed SL, and a ratio L11F of the longitudinal turbulence length scale L11 to the laminar wave thickness δF. Fifteen cases characterized by u/SL = 0.5,1.0,2.0,5.0, or 10.0 and L11F = 2.1, 3.7, or 6.7 are studied. Obtained results show that, while UT is well and unambiguously defined in the considered simplest case of a statistically 1D planar turbulent reaction wave, the wave development can significantly change the scaling exponents. Moreover, the scaling exponents depend on a method used to compare values of UT, i.e., the scaling exponents found by processing the DNS data obtained at the same normalized wave-development time may be substantially different from the scaling exponents found by processing the DNS data obtained at the same normalized wave size. These results imply that the scaling exponents obtained from premixed turbulent flames of different configurations may be different not only due to the well-known effects of the mean-flame-brush curvature and the mean flow non-uniformities, but also due to the flame development, even if the different flames are at the same stage of their development. The emphasized transient effects can, at least in part, explain significant scatter of the scaling exponents obtained by various research groups in different experiments, thus, implying that the scatter in itself is not sufficient to reject the notion of turbulent burning velocity.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Burning velocity, Consumption velocity, DNS, Premixed turbulent combustion, Turbulent flame development
in
Flow, Turbulence and Combustion
volume
102
issue
3
pages
679 - 698
publisher
Springer
external identifiers
  • scopus:85053530995
ISSN
1386-6184
DOI
10.1007/s10494-018-9982-7
language
English
LU publication?
yes
id
71faf7fa-638b-4076-a674-10d7d503ea2e
date added to LUP
2018-10-24 08:43:03
date last changed
2019-09-17 04:41:49
@article{71faf7fa-638b-4076-a674-10d7d503ea2e,
  abstract     = {<p>3D Direct Numerical Simulations of propagation of a single-reaction wave in forced, statistically stationary, homogeneous, isotropic, and constant-density turbulence, which is not affected by the wave, are performed in order to investigate the influence of the wave development on scaling (power) exponents for the turbulent consumption velocity U<sub>T</sub> as a function of the rms turbulent velocity u<sup>′</sup>, laminar wave speed S<sub>L</sub>, and a ratio L<sub>11</sub>/δ<sub>F</sub> of the longitudinal turbulence length scale L<sub>11</sub> to the laminar wave thickness δ<sub>F</sub>. Fifteen cases characterized by u<sup>′</sup>/S<sub>L</sub> = 0.5,1.0,2.0,5.0, or 10.0 and L<sub>11</sub>/δ<sub>F</sub> = 2.1, 3.7, or 6.7 are studied. Obtained results show that, while U<sub>T</sub> is well and unambiguously defined in the considered simplest case of a statistically 1D planar turbulent reaction wave, the wave development can significantly change the scaling exponents. Moreover, the scaling exponents depend on a method used to compare values of U<sub>T</sub>, i.e., the scaling exponents found by processing the DNS data obtained at the same normalized wave-development time may be substantially different from the scaling exponents found by processing the DNS data obtained at the same normalized wave size. These results imply that the scaling exponents obtained from premixed turbulent flames of different configurations may be different not only due to the well-known effects of the mean-flame-brush curvature and the mean flow non-uniformities, but also due to the flame development, even if the different flames are at the same stage of their development. The emphasized transient effects can, at least in part, explain significant scatter of the scaling exponents obtained by various research groups in different experiments, thus, implying that the scatter in itself is not sufficient to reject the notion of turbulent burning velocity.</p>},
  author       = {Yu, Rixin and Lipatnikov, Andrei N.},
  issn         = {1386-6184},
  keyword      = {Burning velocity,Consumption velocity,DNS,Premixed turbulent combustion,Turbulent flame development},
  language     = {eng},
  number       = {3},
  pages        = {679--698},
  publisher    = {Springer},
  series       = {Flow, Turbulence and Combustion},
  title        = {A DNS Study of Sensitivity of Scaling Exponents for Premixed Turbulent Consumption Velocity to Transient Effects},
  url          = {http://dx.doi.org/10.1007/s10494-018-9982-7},
  volume       = {102},
  year         = {2019},
}