Dissipation and dilatation rates in premixed turbulent flames

Sabelnikov, Vladimir; Lipatnikov, Andrei; Nishiki, Shinnosuke; Dave, Himanshu; Perez, F.E. Hernandez; Song, Wonsik; Johansson, Bengt

doi:10.1063/5.0039101

Cited by 14 publications

(11 citation statements)

References 83 publications

(94 reference statements)

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“…For instance, in a DNS study by Chen and Im, 38,39 such effects were shown to be weak even at lower Φ = 0.7. Statistically significant differential diffusion effects were not revealed in recent analyses 15,17,40 of other 14 DNS data obtained from lean hydrogen-air flames characterized by Φ = 0.7. Moreover, Fig.…”

Section: Resultsmentioning

confidence: 82%

“…Indeed, for lean hydrogen-air flames, (i) such phenomena are known 37 to result in increasing (decreasing) the local temperature, equivalence ratio, HRR, and fuel consumption rate in positively (negatively, i.e., the curvature center in the unburned reactants) curved reaction zones and (ii) such zones are predominately localized to the leading (trailing) edge of a premixed turbulent flame brush for purely geometrical reasons, e.g., see Fig. 8b in a recent paper by Sabelnikov et al 40 . Thus, even if differential diffusion phenomena weakly affect (for Φ = 0.81) bulk flame characteristics such as 𝑈 𝑡 𝐻𝑅𝑅 (𝑡), see Fig.…”

Section: Resultsmentioning

confidence: 99%

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Flame folding and conditioned concentration profiles in moderately intense turbulence

Lipatnikov

2022

Physics of Fluids

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While the flamelet paradigm offers the opportunity to simplify computations of mean species concentrations in turbulent flames, a widely accepted criterion of the validity of this paradigm has not yet been elaborated. In this regard, different physical mechanisms are discussed, and flame folding is one of them. The present work aims at exploring the eventual influence of flame folding on the local flame structure in a turbulent flow. For this purpose, a new diagnostic technique was applied to processing complex-chemistry direct numerical simulation data obtained earlier from a lean hydrogen-air turbulent flame [H.L. Dave and S. Chaudhuri, J. Fluid Mech. 884, A46 (2020)]. The technique consists of counting crossing numbers Nf for a cold boundary of the local reaction zone and a ray normal to the mean flame brush, followed by analyzing statistics sampled from rays characterized by Nf{greater than or equal to}3. More specifically, profiles of species mole fractions, temperature, heat release rate, and species production rates, conditioned to combustion progress variable and either Nf or axial distance Δx between two neighboring reaction zones, are sampled and compared with the counterpart profiles obtained from the laminar flame. Results show that these doubly conditioned profiles are close to each other for various crossing numbers or for various axial distances even if the distance is as small as half laminar flame thickness. The lack of a substantial effect of the crossing number or the axial distance on the doubly conditioned profiles implies that small-scale flame folding does not limit the validity of the flamelet paradigm.

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Flame folding and conditioned concentration profiles in moderately intense turbulence

Lipatnikov

2022

Physics of Fluids

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“…This enthusiastic response is another indication of the respect Ted O'Brien has within the international research community of turbulence and reactive flows. These contributions are on diverse topics including combustion instability, 150,151 scalar mixing, [152][153][154][155][156] homogeneous isotropic turbulence, [157][158][159][160] turbulent premixed flames, [161][162][163][164][165][166][167][168][169][170][171] turbulent non-premixed flames, [172][173][174][175] wallbounded turbulence, [176][177][178] turbulent combustion modeling, [179][180][181] FDF/PDF, [182][183][184][185][186][187][188][189][190][191][192] and two-phase turbulent flows. [193][194][195][196]<...…”

Section: Organization Of This Simentioning

confidence: 99%

Edward E. O'Brien contributions to reactive-flow turbulence

2021

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Professor Edward Ephraim O'Brien ("Ted") has made lasting contributions to the theory and modeling of scalar mixing and reaction in turbulent flows. With a doctoral dissertation at The Johns Hopkins University in 1960, entitled "On the Statistical Behavior of a Dilute Reactant in Isotropic Turbulence," supervised by the legend Stanley Corrsin, and in the company of notable pioneer of turbulence, John Leask Lumley, Ted's academic training propelled him through a prolific career. In the opening article of this Special Issue, we provide a review of some of Ted's contributions. First, a summary is presented of his work on the examination of the failure of the cumulant discard approximation for the scalar mixing. This is followed by a highlight of his impacts on other spectral theories of turbulence including Kraichnan's direct interaction approximation. His contributions to more modern theoretical/computational description of reactive turbulence are discussed next, including the transported probability density function (pdf) formulation, scalar-gradient pdf transport equation, scalar interfaces, and the filtered density function. Finally, some of his research on Direct Numerical Simulation of compressible turbulence is reviewed.

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“…For this reason, a set of methods applied to explore this influence was greatly extended recently. [10][11][12][13][17][18][19][20][21] In particular, the joint use of conditioned structure function (SF) techniques 17,[24][25][26] and Helmholtz-Accepted to Phys. Fluids 10.1063/5.0096509 Hodge decomposition 27 (HHD) appears to be a promising tool for acquiring fundamental knowledge on turbulence in flames.…”

Section: Introductionmentioning

confidence: 99%

“…The present work aims at applying this newly introduced research tool 28 to DNS data of two turbulent lean H 2 /air flames with detailed chemistry. 21,[29][30][31] In the next section, research methods are presented. Results are reported and discussed in Sect.…”

Section: Introductionmentioning

confidence: 99%

Conditioned structure functions in turbulent hydrogen/air flames

et al. 2022

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Direct numerical simulation data obtained from two turbulent, lean hydrogen-air flames propagating in a box are analyzed to explore the influence of combustion-induced thermal expansion on turbulence in unburned gas. For this purpose, Helmholtz-Hodge decomposition is applied to the computed velocity fields. Subsequently, the second-order structure functions conditioned to unburned reactants are sampled from divergence-free solenoidal velocity field or irrotational potential velocity field, yielded by the decomposition. Results show that thermal expansion significantly affects the conditioned potential structure functions not only inside the mean flame brushes, but also upstream of them. Upstream of the flames, firstly, transverse structure functions for transverse potential velocities grow with distance r between sampling points more slowly when compared to the counterpart structure functions sampled from the entire or solenoidal velocity field. Secondly, the former growth rate depends substantially on the distance from the flame-brush leading edge, even at small r. Thirdly, potential root-mean-square (rms) velocities increase with decreasing distance from the flame-brush leading edge and are comparable with solenoidal rms velocities near the leading edge. Fourthly, although the conditioned axial and transverse potential rms velocities are always close to one another, thus, implying isotropy of the potential velocity field in unburned reactants; the potential structure functions exhibit a high degree of anisotropy. Fifthly, thermal expansion effects are substantial even for the solenoidal structure functions and even upstream of a highly turbulent flame. These findings call for development of advanced models of turbulence in flames, which allow for the discussed thermal expansion effects.

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Dissipation and dilatation rates in premixed turbulent flames

Abstract: Paper published as part of the special topic on In Memory of Edward E. (Ted) O'Brien ARTICLES YOU MAY BE INTERESTED IN Turbulence topology evolution in weakly turbulent premixed flames

Cited by 14 publications

References 83 publications

Flame folding and conditioned concentration profiles in moderately intense turbulence

Flame folding and conditioned concentration profiles in moderately intense turbulence

Edward E. O'Brien contributions to reactive-flow turbulence

Conditioned structure functions in turbulent hydrogen/air flames

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