An investigation of the performance of turbulent mixing models

Ren, Zhuyin; Pope, Stephen B.

doi:10.1016/j.combustflame.2003.09.014

Cited by 90 publications

(44 citation statements)

References 13 publications

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“…The numerical observations for the different micro-mixing models' behavior are in line with [2], where a lifted flame was obtained when combining ILDM with CD and C φ = 2 (an attached flame was only obtained when burning laminar flamelet conditions were imposed in a region near the nozzle exit and C φ was increased from 2 to 4). They are also in line with the conclusions of [22], where it is stated that the EMST micro-mixing model, compared to the IEM and CD mixing models, has the strongest resistance to extinction when the mixture fraction variance is high. This is the case in the region near the burner nozzle.…”

Section: Turbulence -Chemistry Interaction Modelsupporting

confidence: 90%

Flow and Mixing Fields for Transported Scalar PDF Simulations of a Piloted Jet Diffusion Flame (‘Delft Flame III’)

Merci

Naud

Roekaerts

2005

Flow Turbulence Combust

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Abstract. Numerical simulation results are presented for 'Delft Flame III', a piloted jet diffusion flame with strong turbulence-chemistry interaction. While pilot flames emerge from 12 separate holes in the experiments, the simulations are performed on a rectangular grid, under the assumption of axisymmetry. In the first part of the paper, flow and mixing field results are presented with a non-linear first order k-ε model, with the transport equation for ε based on a modeled enstrophy transport equation, for cold and reactive flows. For the latter, the turbulence model is applied in combination with pre-assumed β-PDF modeling for the turbulence-chemistry interaction. The mixture fraction serves as conserved scalar. Two chemistry models are considered: chemical equilibrium and a steady laminar flamelet model. The importance of the turbulence model is highlighted. The influence of the chemistry model is noticeable too. A procedure is described to construct appropriate inlet boundary conditions. Still, the generation of accurate inlet boundary conditions is shown to be far less important, their effect being local, close to the nozzle exit. In the second part of the paper, results are presented with the transported scalar PDF approach as turbulencechemistry interaction model. A C 1 skeletal scheme serves as chemistry model, while the EMST method is applied as micro-mixing model. For the transported PDF simulations, the model for the pilot flames, as an energy source term in the mean enthalpy transport equation, is important with respect to the accuracy of the flow field predictions. It is explained that the strong influence on the flow and mixing field is through the turbulent shear stress force in the region, close to the nozzle exit.

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Section: Turbulence -Chemistry Interaction Modelsupporting

confidence: 90%

Flow and Mixing Fields for Transported Scalar PDF Simulations of a Piloted Jet Diffusion Flame (‘Delft Flame III’)

Merci

Naud

Roekaerts

2005

Flow Turbulence Combust

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“…The complex behavior that results from the presence of such effects cannot be accounted for by using simple models and, typically, transported probability density function ͑PDF͒-based models are required. 3 Sensitivities to different closure elements, including molecular mixing, 4 increase during extinction and reignition processes and in the present work the prospects of combining a stochastic multiple mapping conditioning 5 ͑MMC͒ approach with a binomial Langevin model 6 for joint velocity-scalar statistics is evaluated. The current hybrid approach has the advantages of removing implementation difficulties associated with bounded scalars in the context of the binomial Langevin model, and providing simple closures for MMC coefficients ͑which are averages containing reference space and scalar quantities͒.…”

Section: Introductionmentioning

confidence: 99%

Hybrid binomial Langevin-multiple mapping conditioning modeling of a reacting mixing layer

Wandel

Lindstedt

2009

Physics of Fluids

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A novel, stochastic, hybrid binomial Langevin-multiple mapping conditioning ͑MMC͒ model-that utilizes the strengths of each component-has been developed for inhomogeneous flows. The implementation has the advantage of naturally incorporating velocity-scalar interactions through the binomial Langevin model and using this joint probability density function ͑PDF͒ to define a reference variable for the MMC part of the model. The approach has the advantage that the difficulties encountered with the binomial Langevin model in modeling scalars with nonelementary bounds are removed. The formulation of the closure leads to locality in scalar space and permits the use of simple approaches ͑e.g., the modified Curl's model͒ for transport in the reference space. The overall closure was evaluated through application to a chemically reacting mixing layer. The results show encouraging comparisons with experimental data for the first two moments of the PDF and plausible results for higher moments at a relatively modest computational cost.

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“…In recent articles (e.g. [7][8][9][10][11][12]), differences in the micro-mixing model behavior have been investigated. As a first step, it is common practice to make sure that the numerical predictions in physical space are as accurate as possible.…”

Section: Introductionmentioning

confidence: 99%

Impact of Turbulent Flow and Mean Mixture Fraction Results on Mixing Model Behavior in Transported Scalar PDF Simulations of Turbulent Non-premixed Bluff Body Flames

Merci

Naud²,

Roekaerts

2007

Flow Turbulence Combust

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Numerical simulation results are presented for three turbulent jet diffusion flames, stabilized behind a bluff body . Interaction between turbulence and combustion is modeled with the transported joint-scalar PDF approach. The focus of the study is on the impact of the quality of simulation results in physical space on the behavior of two micro-mixing models in composition space: the Euclidean Minimum Spanning Tree ('EMST') model and the modified Curl coalescence dispersion ('CD') model. Profiles of conditional means and variances of thermo-chemical quantities, conditioned on the mixture fraction, are discussed in the recirculation region and in the neck zone behind. The impact of the flow and mixing fields in physical space on the mixing model behavior in composition space is strong for the CD model and increases as the turbulence -chemistry interaction becomes stronger. The EMST conditional profiles, on the contrary, are hardly affected.Key words transported scalar PDF . micro-mixing models . turbulent non-premixed flames . bluff body

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An investigation of the performance of turbulent mixing models

Cited by 90 publications

References 13 publications

Flow and Mixing Fields for Transported Scalar PDF Simulations of a Piloted Jet Diffusion Flame (‘Delft Flame III’)

Flow and Mixing Fields for Transported Scalar PDF Simulations of a Piloted Jet Diffusion Flame (‘Delft Flame III’)

Hybrid binomial Langevin-multiple mapping conditioning modeling of a reacting mixing layer

Impact of Turbulent Flow and Mean Mixture Fraction Results on Mixing Model Behavior in Transported Scalar PDF Simulations of Turbulent Non-premixed Bluff Body Flames

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