Evolution of averaged local premixed flame thickness in a turbulent flow

Yu, Rixin; Nillson, Thommie; Bai, Xue‐Song; Lipatnikov, Andrei

doi:10.1016/j.combustflame.2019.05.045

Cited by 21 publications

(16 citation statements)

References 65 publications

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“…At the same time, it is worth noting that while various thermal expansion effects were revealed in premixed turbulent flames, the latest review articles (Lipatnikov and Chomiak 2010;Sabelnikov and Lipatnikov 2017) do not refer to any study that documents a substantial influence of thermal expansion on the density-weighted displacement speed ( S d ) . This fact, as well as the recent DNS study (Yu et al 2019) discussed in the end of the previous section, suggest that results obtained from a constant-density turbulent reaction wave can be useful for understanding the influence of turbulence on a premixed flame.…”

Section: Evolution Equation For Displacement Speedmentioning

confidence: 61%

“…Since the DNS attributes are discussed in detail elsewhere (Yu et al , 2015(Yu et al , 2019Lipatnikov 2017a, b, 2019b;Elperin et al 2016;Sabelnikov et al 2019b), we will restrict ourselves to a brief summary of the simulations.…”

Section: Dns Databasementioning

confidence: 99%

“…In this regard, it is worth remembering that we recently explored the evolution of various measures of local flame thickness (e.g. |∇c| or 1∕|∇c| ) conditionally averaged on the reaction progress variable c by analyzing DNS data obtained from (i) a constant-density single-reaction wave (the same DNS data are considered in the present work), (ii) two single-step-chemistry premixed turbulent flames with heat release and density variations, and (iii) two complexchemistry premixed turbulent flames (Yu et al 2019). As shown in the cited paper, see p. 240, "the major features of the transient evolutions of all thicknesses are similar in different (constant density and single-step-chemistry, variable density and single-step chemistry, variable density and complex chemistry) cases".…”

Section: Introductionmentioning

confidence: 99%

“…(13), to study highly disturbed turbulent reaction waves. For this purpose, a representative highly turbulent case (case C in the following) is selected from a large DNS database(Yu et al , 2015(Yu et al , 2019 Yu and Lipatnikov 2017a, b, (20) t ( c) + ∇ ⋅ ( uc) = ( + ) = ( S d )|∇c|,…”

mentioning

confidence: 99%

See 3 more Smart Citations

Assessment of an Evolution Equation for the Displacement Speed of a Constant-Density Reactive Scalar Field

Nilsson

Brethouwer

et al. 2020

Flow Turbulence Combust

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The displacement speed that characterises the self-propagation of isosurfaces of a reaction progress variable is of key importance for turbulent premixed reacting flow. The evolution equation for the displacement speed was derived in a recent work of Yu and Lipatnikov (Phys Rev E 100:013107, 2019a) for the case where the flame is described by a transport equation for single reaction progress variable assuming simple transport and one-step chemistry. This equation represents interaction of a number of complex coupled mechanisms related to straining by the velocity field, surface curvature and the scalar gradient. The aim of the current work is to provide detailed physical explanations of the displacement speed equation and its various terms, and to provide a new perspective to understand the mechanisms responsible for observed variations in the displacement speed. The equation is then used to analyze the propagation of a statistically planar reaction wave in homogeneous isotropic constant-density turbulence using direct numerical simulations. Additional emphasis is put on retracting surface segments that have a negative displacement speed, a phenomenon that commonly occurs at high Karlovitz numbers.

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Section: Evolution Equation For Displacement Speedmentioning

confidence: 61%

Section: Dns Databasementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Assessment of an Evolution Equation for the Displacement Speed of a Constant-Density Reactive Scalar Field

Nilsson

Brethouwer

et al. 2020

Flow Turbulence Combust

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“…A common feature of the transport equation (26) [72]. Contributions of the aforementioned terms to the evolutions of various surface averaged |∇c| and 1/|∇c| will be discussed in a followup paper [73]. Here, we restrict ourselves to noting that the stretch-rate (self-propagation) terms work to increase (decrease, respectively) |∇c| and make the flame thinner (thicker, respectively), whereas the dilatation terms play a minor role in developing highly turbulent flames.…”

Section: Particular Evolution Equations For Surface-averaged Quantmentioning

confidence: 99%

Surface-averaged quantities in turbulent reacting flows and relevant evolution equations

Lipatnikov

2019

Phys. Rev. E

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While quantities conditioned to an isosurface of reaction progress variable c, which characterizes fluid state in a turbulent reacting flow, have been attracting rapidly growing interest in the recent literature, a mathematical and physical framework required for research into such quantities has not yet been elaborated properly. This paper aims at filling two fundamental gaps in this area, i.e., (i) ambiguities associated with a definition of a surface-averaged quantity and (ii) the lack of rigorous equations that describe evolutions of such quantities. In the first (theoretical) part of the paper, (a) analytical relations between differently defined (area-weighted and unweighted) surface-averaged quantities are obtained and differences between them (quantities) are discussed, (b) a unified method for deriving an evolution equation for bulk area-weighted surface-averaged value of a local characteristic φ of a turbulent reacting flow is developed, and (c) the method is applied for deriving evolution equations for the bulk area-weighted surface-averaged reaction-surface density |∇c|, local reactionwave thickness 1/|∇c|, and local displacement speed S d , i.e., the speed of an isosurface of the c(x, t) field with respect to the local flow. In the second (numerical) part of the paper, direct numerical simulation data obtained recently from a highly turbulent reaction wave are analyzed in order to (1) highlight substantial differences between area-weighted and unweighted surface-averaged quantities and (2) show that various terms in the derived evolution equations are amenable to accurate numerical evaluation in spite of appearance of the so-called zero-gradient points [C. H. Gibson, Phys. Fluids 11, 2305 (1968)] in a highly turbulent medium. Finally, the obtained analytical and numerical results are used to shed light on the paradox of local flame thinning and broadening which is widely discussed in the turbulent combustion literature.

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Regimes of Premixed Flames

Liberman

2021

Combustion Physics

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Evolution of averaged local premixed flame thickness in a turbulent flow

Cited by 21 publications

References 65 publications

Assessment of an Evolution Equation for the Displacement Speed of a Constant-Density Reactive Scalar Field

Assessment of an Evolution Equation for the Displacement Speed of a Constant-Density Reactive Scalar Field

Surface-averaged quantities in turbulent reacting flows and relevant evolution equations

Regimes of Premixed Flames

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