A DNS Study of Sensitivity of Scaling Exponents for Premixed Turbulent Consumption Velocity to Transient Effects
(2019) In Flow, Turbulence and Combustion 102(3). p.679698 Abstract
3D Direct Numerical Simulations of propagation of a singlereaction wave in forced, statistically stationary, homogeneous, isotropic, and constantdensity 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_{T} as a function of the rms turbulent velocity u^{′}, laminar wave speed S_{L}, and a ratio L_{11}/δ_{F} of the longitudinal turbulence length scale L_{11} to the laminar wave thickness δ_{F}. Fifteen cases characterized by u^{′}/S_{L} = 0.5,1.0,2.0,5.0, or 10.0 and L_{11}/δ_{F} = 2.1, 3.7, or 6.7 are... (More)
3D Direct Numerical Simulations of propagation of a singlereaction wave in forced, statistically stationary, homogeneous, isotropic, and constantdensity 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_{T} as a function of the rms turbulent velocity u^{′}, laminar wave speed S_{L}, and a ratio L_{11}/δ_{F} of the longitudinal turbulence length scale L_{11} to the laminar wave thickness δ_{F}. Fifteen cases characterized by u^{′}/S_{L} = 0.5,1.0,2.0,5.0, or 10.0 and L_{11}/δ_{F} = 2.1, 3.7, or 6.7 are studied. Obtained results show that, while U_{T} 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_{T}, i.e., the scaling exponents found by processing the DNS data obtained at the same normalized wavedevelopment 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 wellknown effects of the meanflamebrush curvature and the mean flow nonuniformities, 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
 Yu, Rixin ^{LU} and Lipatnikov, Andrei N.
 organization
 publishing date
 2019
 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
 13866184
 DOI
 10.1007/s1049401899827
 language
 English
 LU publication?
 yes
 id
 71faf7fa638b4076a67410d7d503ea2e
 date added to LUP
 20181024 08:43:03
 date last changed
 20190917 04:41:49
@article{71faf7fa638b4076a67410d7d503ea2e, abstract = {<p>3D Direct Numerical Simulations of propagation of a singlereaction wave in forced, statistically stationary, homogeneous, isotropic, and constantdensity 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 wavedevelopment 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 wellknown effects of the meanflamebrush curvature and the mean flow nonuniformities, 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 = {13866184}, keyword = {Burning velocity,Consumption velocity,DNS,Premixed turbulent combustion,Turbulent flame development}, language = {eng}, number = {3}, pages = {679698}, 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/s1049401899827}, volume = {102}, year = {2019}, }