Modelling of turbulent lifted jet flames using flamelets:<i>a priori</i>assessment and<i>a posteriori</i>validation

Ruan, S.; Swaminathan, Nedunchezhian; Darbyshire, Oliver

doi:10.1080/13647830.2014.898409

Cited by 66 publications

(124 citation statements)

References 66 publications

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“…Using the simplifications implied by the resolution of the flamelets in Z-space (as usually done in other UFPV approaches), we choose to consider a log-normal distribution for f χ st (different from [4][5][6]) while a non-normalised progress variable is used (different from [11][12][13]15]). We do not assume statistical independence between the progress variable and mixture fraction as often considered in presumed PDF modelling (unless their correlation is included as done in [47,48] using a copula). Instead, we make an assumption of statistical independence using the time evolution of the unsteady flamelet, allowing us to keep a physical dependence between Y c and Z.…”

Section: Presumed Pdf Modellingmentioning

confidence: 99%

RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF

Naud

Novella

Pastor

et al. 2015

Combustion and Flame

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Elsevier Naud, B.; Novella Rosa, R.; Pastor Enguídanos, JM.; Winklinger, JF. (2015). RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF. Combustion and Flame. 162 (4) AbstractAn unsteady flamelet / progress variable (UFPV) approach is used to model a lifted H 2 /N 2 flame in a RANS framework together with presumed PDF. We solve the unsteady flamelets both in physical space and in mixture fraction space. We show that in the former case, the scalar dissipation rate profile strongly varies in time (while it is assumed to be fixed in time in the latter). However, this does not result in significant qualitative differences in the corresponding flamelet libraries. The progress variable is carefully defined, including both the main combustion product (H 2 O) and a key radical species in ignition process (HO 2 ). The presumed-PDF model is proposed in terms of the non-normalised progress variable, without assuming its statistical independence with mixture fraction. We introduce a modelled transport equation for the mean progress variable which is consistent with the basic underlying UFPV assumption, derived from the Lagrangian flamelet model. The influence of different model parameters on the results for the mean temperature and mean species mass fractions and their fluctuations is discussed. Good results are obtained for the conditions of the considered lifted flame where detailed experimental data is available. However, at low coflow temperature the modelled flame lift-off height is shorter than expected.

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Section: Presumed Pdf Modellingmentioning

confidence: 99%

RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF

Naud

Novella

Pastor

et al. 2015

Combustion and Flame

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“…The termcð1 ÀcÞ=β c comes from combined influences of flame front curvature effects induced by turbulence, chemical reaction, and molecular dissipation processes Chakraborty and Swaminathan, 2007). Although a reasonably robust value of β c ¼ 6:7 was established in past RANS calculations of various premixed flames (Ahmed and Swaminathan, 2013;Amzin and Swaminathan, 2013;Amzin et al, 2012;Kolla et al, 2009;Ruan et al, 2014;Swaminathan et al, 2012), this value cannot be used for LES because the processes influencing β c are effected by SGS turbulence. Thus, it can be evaluated dynamically as suggested by Langella et al (2015) and Gao et al (2014).…”

Section: Algebraic Closure For Filtered Reaction Ratementioning

confidence: 99%

“…The past studies Swaminathan, 2013, 2014;Kolla et al, 2009;Kolla and Swaminathan, 2010b;Ruan et al, 2014;Swaminathan et al, 2012) showed that the above parameterization is not arbitrary and various terms in Eq. (2) are closely related to certain physical processes involved in the transport of scalar dissipation rate Kolla et al, 2009).…”

Section: Algebraic Closure For Filtered Reaction Ratementioning

confidence: 99%

“…where T 0 ¼ 298:13 K and e C p;mix is the specific heat capacity at constant pressure for the mixture, which depends on temperature as described by Ruan et al (2014). The fluid mixture density is computed using the state equation ρ ¼ p e W mix =ðR e TÞ; where " p is the filtered pressure, e W mix is the Favre-filtered molecular mass of the mixture and R is the universal gas constant.…”

Section: Simulation Detailmentioning

confidence: 99%

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Large Eddy Simulation of Premixed Combustion: Sensitivity to Subgrid Scale Velocity Modeling

Langella

Swaminathan

Gao

et al. 2016

Combustion Science and Technology

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An algebraic reaction rate closure involving filtered scalar dissipation rate of reaction progress variable is studied. The filtered scalar dissipation rate closure requires a model for sub-grid scale velocity, u 0 Δ , which is estimated using four algebraic models and transported subgrid scale kinetic energy. A priori analyses using direct numerical simulation (DNS) data show that the filtered dissipation rate, and thus the reaction rate closure, has some sensitivity to the u 0 Δ model. The sensitivity of various statistics obtained from large eddy simulation (LES) of three piloted Bunsen flames of stoichiometric methaneair mixture to the modeling of u 0 Δ is observed to be weaker compared to that for the DNS analysis. Moreover, analysis using transported sub-grid scale kinetic energy does not indicate a necessity to include flame-generated turbulence in the modeling of u 0 Δ for the Bunsen flames in the thin reaction zones regime. The measured and computed flame brush structures are compared and studied and the algebraic closure for the filtered reaction rate is found to be quite good. ARTICLE HISTORY

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“…In the Reynolds-averaged Navier-Stokes (RANS) context, the effect of this correlation has been assessed previously by Ruan et al [7] and Chen et al [8] using a presumed joint probability density function (JPDF) approach for turbulent lifted flames. The statistical correlation was included in the JPDF using a copula method [7,9].…”

Section: Introductionmentioning

confidence: 99%

A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames

Chen

Doan

Ruan

et al. 2018

Combustion Theory and Modelling

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Subgrid correlation of mixture fraction, Z, and progress variable, c, is investigated using direct numerical dimulation (DNS) data of a hydrogen lifted jet flame. Joint subgrid behaviour of these two scalars are obtained using a Gaussian-type filter for a broad range of filter sizes. A joint probability density function (JPDF) constructed using single-snapshot DNS data is compared qualitatively with that computed using two independent β-PDFs and a copula method. Strong negative correlation observed at different streamwise locations in the flame is captured well by the copula method. The subgrid contribution to the Z-c correlation becomes important if the filter is of the size of the laminar flame thickness or larger. A priori assessment for the filtered reaction rate using the flamelet approach with independent β-PDFs and correlated JPDF is then performed. Comparison with the DNS data shows that both models provide reasonably good results for a range of filter sizes. However, the reaction rate computed using copula JPDF is found to have a better agreement with the DNS data for large filter sizes because the subgrid Z-c correlation effect is included.

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Modelling of turbulent lifted jet flames using flamelets:a prioriassessment anda posteriorivalidation

Cited by 66 publications

References 66 publications

RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF

RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF

Large Eddy Simulation of Premixed Combustion: Sensitivity to Subgrid Scale Velocity Modeling

A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames

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