A-Priori Direct Numerical Simulation Modelling of Co-variance Transport in Turbulent Stratified Flames

Malkeson, Sean P.; Chakraborty, Nilanjan

doi:10.1007/s10494-012-9430-z

Cited by 8 publications

(7 citation statements)

References 37 publications

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“…Explicit time advancement uses low storage 3rd-order Runge-Kutta scheme [28]. The numerical technique used in this study is standard practice for combustion DNS and has been used in different DNS analyses in the past [1][2][3][4][5][6][7][8][9][10][11][12][13]. The four boundaries transverse to the mean direction of the flame propagation are considered periodic, while the two boundaries in the direction of the mean flame propagation are considered to be a partially non-reflecting turbulent inflow and outflow in line with the Navier-Stokes characteristic boundary conditions (NSCBC) [29].…”

Section: Dns Databasementioning

confidence: 99%

“…Therefore, scalar forcing does not affect the mode of combustion and thus does not introduce any artificial effects into the flame statistics. [11,42,43]. The cross-scalar dissipation rate N cξ exists within the flame where the scalar forcing does not remain active.…”

Section: Sf + Vfmentioning

confidence: 99%

“…Without any external scalar fluctuation generating mechanism, a statistically quasi-stationary state can only be achieved once the reactants have become perfectly mixed (i.e., premixed combustion). As such, many DNS studies of turbulent stratified-mixture combustion have relied on unsteady decaying turbulence conditions (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13]). However, mixture inhomogeneity in the unburned gas can be sustained with scalar forcing by including an additional term in the species conservation equations, which can be utilised to reach a quasi-steady state for stratified-mixture combustion.…”

Section: Introductionmentioning

confidence: 99%

“…Lipatnikov [14] and Domingo et al [15] provided an extensive review of experimental and numerical findings of stratified-mixture combustion. High-performance computing has enabled DNS of stratified-mixture combustion [1][2][3][4][5][6][7][8][9][10][11][12][13][16][17][18][19], and the vast majority of these studies have been conducted for statistically planar flames in canonical 'flame-in-a-box' configuration [1][2][3][4][5][6][7][8][9][10][11][12][13]. Richardson and Chen [16] and Brearley et al [19] analysed turbulent stratified-mixture combustion using three-dimensional DNS to analyse the effects of the relative alignments of equivalence ratio and reaction progress variable gradients on the global behaviours of burning, flame propagation rate and flame surface area and their modelling implications.…”

Section: Introductionmentioning

confidence: 99%

“…The aforementioned DNS analyses on turbulent stratified-mixture combustion offered fundamental physical information on the stratified flame structure [1][2][3]5,8,13,16,18,19] and flame propagation rate [4,12,16,18]. This information was subsequently utilised to develop closure methodologies for scalar variances and co-variances [3,5,11], turbulent scalar flux [9], flame surface density [10,19], and scalar dissipation and cross-scalar dissipation rates [7,8,13].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Implications of Using Scalar Forcing to Sustain Reactant Mixture Stratification in Direct Numerical Simulations of Turbulent Combustion

Brearley,

Ahmed,

Chakraborty

2024

Computation

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A recently proposed scalar forcing scheme that maintains the mixture fraction mean, root-mean-square and probability density function in the unburned gas can lead to a statistically quasi-stationary state in direct numerical simulations of turbulent stratified combustion when combined with velocity forcing. Scalar forcing alongside turbulence forcing leads to greater values of turbulent burning velocity and flame surface area in comparison to unforced simulations for globally fuel-lean mixtures. The sustained unburned gas mixture inhomogeneity changes the percentage shares of back- and front-supported flame elements in comparison to unforced simulations, and this effect is particularly apparent for high turbulence intensities. Scalar forcing does not significantly affect the heat release rates due to different modes of combustion and the micro-mixing rate within the flame characterised by scalar dissipation rate of the reaction progress variable. Thus, scalar forcing has a significant potential for enabling detailed parametric studies as well as providing well-converged time-averaged statistics for stratified-mixture combustion using Direct Numerical Simulations in canonical configurations.

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Section: Dns Databasementioning

confidence: 99%

Section: Sf + Vfmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Implications of Using Scalar Forcing to Sustain Reactant Mixture Stratification in Direct Numerical Simulations of Turbulent Combustion

Brearley,

Ahmed,

Chakraborty

2024

Computation

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Modelling of Variance and Co-variance in Turbulent Flame–Droplet Interaction: A Direct Numerical Simulation Analysis

Malkeson¹,

Wacks

Chakraborty

2017

Energy, Environment, and Sustainability

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A Priori Direct Numerical Simulation Analysis of the Closure of Cross-Scalar Dissipation Rate of Reaction Progress Variable and Mixture Fraction in Turbulent Stratified Flames

Brearley

Ahmed

Chakraborty

2022

Flow Turbulence Combust

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The cross-scalar dissipation rate of reaction progress variable and mixture fraction $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ plays an important role in the modelling of stratified combustion. The evolution and statistical behaviour of $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ have been analysed using a direct numerical simulation (DNS) database of statistically planar turbulent stratified flames with a globally stochiometric mixture. A parametric analysis has been conducted by considering a number of DNS cases with a varying initial root-mean-square velocity fluctuation $$u^{\prime }$$ u ′ and initial scalar integral length scale $$\ell_{\phi }$$ ℓ ϕ . The explicitly Reynolds averaged DNS data suggests that the linear relaxation model for $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ is inadequate for most cases, but its performance appears to improve with increasing initial $$\ell_{\phi }$$ ℓ ϕ and $$u^{\prime }$$ u ′ values. An exact transport equation for $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ has been derived from the first principle, and the budget of the unclosed terms of the $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ transport equation has been analysed in detail. It has been found that the terms arising from the density variation, scalar-turbulence interaction, chemical reaction rate and molecular dissipation rate play leading order roles in the $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ transport. These observations have been justified by a scaling analysis, which has been utilised to identify the dominant components of the leading order terms to aid model development for the unclosed terms of the $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ transport equation. The performances of newly proposed models for the unclosed terms have been assessed with respect to the corresponding terms extracted from DNS data, and the newly proposed closures yield satisfactory predictions of the unclosed terms in the $$\widetilde{{\varepsilon_{c\xi } }}$$ ε c ξ ~ transport equation.

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A-Priori Direct Numerical Simulation Modelling of Co-variance Transport in Turbulent Stratified Flames

Cited by 8 publications

References 37 publications

Implications of Using Scalar Forcing to Sustain Reactant Mixture Stratification in Direct Numerical Simulations of Turbulent Combustion

Implications of Using Scalar Forcing to Sustain Reactant Mixture Stratification in Direct Numerical Simulations of Turbulent Combustion

Modelling of Variance and Co-variance in Turbulent Flame–Droplet Interaction: A Direct Numerical Simulation Analysis

A Priori Direct Numerical Simulation Analysis of the Closure of Cross-Scalar Dissipation Rate of Reaction Progress Variable and Mixture Fraction in Turbulent Stratified Flames

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