Micromixing models for turbulent flows

Meyer, Daniel W.; Jenny, Patrick

doi:10.1016/j.jcp.2008.10.019

Cited by 33 publications

(28 citation statements)

References 38 publications

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“…[78,79] for comparison of the accuracy of different PDF mixing models). On the contrary, the IEM model performs reasonably well in FDF/LES simulations.…”

Section: The Filtered Density Function (Fdf) Approachmentioning

confidence: 99%

Transport and Mixing in Liquid Phase Using Large Eddy Simulation: A Review

Mejía¹,

Sadiki²,

Chejne³

et al. 2016

Numerical Simulation - From Brain Imaging to Turbulent Flows

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Many mixing processes in engineering applications are turbulent. At high-Schmidt regime, the scalar scales are much lower than those of the velocity field, making difficult instantaneous measurements and direct numerical simulation for studying systems of practical interest. The use of large eddy simulation (LES) for analyzing transport and mixing of passive and reactive scalars at high-Schmidt (Sc) regime is addressed in this article. We present two different approaches for studying scalar transport and mixing in LES: the conventional approach is based on the modeling of the unclosed subgridscale scalar flux term in the filtered scalar equation by models commonly used for highSc flows. The second approach presented in this review for dealing with high-Sc flows is based on the use of a filtered mass density function (FDF) of the scalar field. Conclusions are presented about the relative merits of the two approaches.

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“…[78,79] for comparison of the accuracy of different PDF mixing models). On the contrary, the IEM model performs reasonably well in FDF/LES simulations.…”

Section: The Filtered Density Function (Fdf) Approachmentioning

confidence: 99%

Transport and Mixing in Liquid Phase Using Large Eddy Simulation: A Review

Mejía¹,

Sadiki²,

Chejne³

et al. 2016

Numerical Simulation - From Brain Imaging to Turbulent Flows

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“…However, the use of a mean turbulence frequency /k in the EMST mixing model implies a strong limitation in order to model high χ * CO 2 events. A mixing model based on a scalar dissipation rate of the form of Equation (4) including a modeled fluctuating turbulence frequency ω * like the PSP mixing model [7][8][9][10] could provide a better framework in order to model local extinction.…”

Section: Characteristic Regions In Composition Spacementioning

confidence: 99%

“…Moreover, in a RANS framework, the flow and mixing fields in physical space are steady and not all fluctuations in scalar dissipation rate can be expected to be captured. The PSP model [7][8][9][10], which uses one-dimensional parametrized scalar profiles (PSPs) to model the unresolved scalar lengthscales characterizing the scalar micro-mixing, can capture the fluctuations in scalar dissipation rate better, as it provides joint statistics of scalars and their scalar dissipation rate. In LES, resolved fluctuations in instantaneous flow and mixing fields result in resolved fluctuations of the scalar dissipation rate.…”

Section: Introductionmentioning

confidence: 99%

Transported scalar PDF calculations of a swirling bluff body flame (‘SM1’) with a reaction diffusion manifold

Meester

Naud

Maas

et al. 2012

Combustion and Flame

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The modeling of a reacting swirling flow behind a bluff-body burner (SM1) in the framework of RANS and transported scalar PDF is presented. The EMST mixing model is applied and the composition space is reduced to mixture fraction (Z) and a progress variable (CO 2 mass fraction, Y CO 2 ) by means of a Reaction Diffusion Manifold (REDIM). With an ad hoc adjustment of the turbulent Schmidt number, the mean flow and mixing fields obtained are comparable to LES results from the literature. The REDIM reduction of the composition space to (Z, Y CO 2 ) is discussed and its validity for the present swirling flame is first considered by an a priori comparison with experimental data. The (Z, Y CO 2 )-scatter plots from the transported PDF calculation show the capacity to reproduce the mixing between fresh air and hot products in the recirculation zone above the bluff-body. However, too little scatter is observed. The study of tracer trajectories helps to better understand the capacities and limitations of the modeling approach. Zones where mixing competes with reaction can be identified, and coincide with the highly rotating collar region where local extinction is expected to take place. However, in our modeling, the competition between mixing and reaction is not enough to lead to local extinction. An important modeling deficiency is claimed to be the use of a mean time scale in the EMST mixing model, which limits the possibilities to model high scalar dissipation rate events.

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“…For the homogeneous turbulent flow, the micromixing problem [2,3,5,8] must be resolved in this PDF equation. At the initial mixing time, a scalar field is segregated and no domains with intermediate f values exist.…”

Section: Averaged Reaction Rate Dependence Of Mixture Fraction Pdf Thmentioning

confidence: 99%

“…So, the well-developed homogeneous turbulence theory [7] is used for closing the micromixing models. Just the adequate description of micromixing, connected not only with the successful modeling of chemical source terms but first with a reasonable analysis of the entire mixing process, remains a stumbling block for the PDF method [2,3,5,8]. This problem has received particular attention in the present work where the problem on mixing with chemical reaction in the homogeneous turbulent flow is stated using both the method of statistical moments for fluid dynamic characteristics and the mixture fraction PDF method for closing unknown correlations responsible for the chemical reaction.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Micromixing Models for Calculation of the Chemical Reaction Rate in Homogeneous Turbulent Flow

Chorny

2009

Chem Eng & Technol

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Turbulent mixing with a single second-order isothermal reaction in a homogeneous flow is considered. A mixing model is stated using the probability density function (PDF) equation method and the concepts of mixture fraction and progress variable. Different micromixing models are compared. With the interaction exchange mean/linear square mean estimation (IEM/LSME) model, the time variation of the mixture fraction PDF contradicts the physical representation of mixing. The Langevin model describes mixing from the segregating state to the homogeneous state of a mixture. The PDF model proves to be two-mode at intermediate mixing stages. This is also true for the multi-zone PDF model. As compared to the multi-zone PDF model, others reveal higher averaged progress variables over the entire time range and at all Damköhler number values. Such a difference is made by the approximations for the averaged reaction rate that should be allowed for in the modeling of turbulent mixing with chemical reaction.

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Micromixing models for turbulent flows

Cited by 33 publications

References 38 publications

Transport and Mixing in Liquid Phase Using Large Eddy Simulation: A Review

Transport and Mixing in Liquid Phase Using Large Eddy Simulation: A Review

Transported scalar PDF calculations of a swirling bluff body flame (‘SM1’) with a reaction diffusion manifold

Comparison of Micromixing Models for Calculation of the Chemical Reaction Rate in Homogeneous Turbulent Flow

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