A generalised multiple mapping conditioning approach for turbulent combustion

Cleary, Matthew and Klimenko, Alexander Y. (2009) A generalised multiple mapping conditioning approach for turbulent combustion. Flow, Turbulence and Combustion, 82 4: 477-491.


Author Cleary, Matthew
Klimenko, Alexander Y.
Title A generalised multiple mapping conditioning approach for turbulent combustion
Journal name Flow, Turbulence and Combustion   Check publisher's open access policy
ISSN 1386-6184
Publication date 2009-06
Year available 2008
Sub-type Article (original research)
DOI 10.1007/s10494-008-9161-3
Volume 82
Issue 4
Start page 477
End page 491
Total pages 15
Editor K. Hanjalic
Place of publication Netherlands
Publisher Springer Netherlands
Collection year 2009
Language eng
Subject C1
Abstract This paper follows the evolution in understanding of the multiple mapping conditioning (MMC) approach for turbulent combustion and reviews different implementations of MMC models. As the MMC name suggests, the original version represents a consistent combination of CMC-type conditional equations (conditional moment closure) and generalised mapping closure. It seems that the strength of the MMC model, and especially that of its stochastic version, lies in a more general (and much more transparent) interpretation. In this new generalised interpretation, we can replace complicated derivations by physical reasoning and the model appears to be a natural extension of modelling approaches developed in recent decades. MMC can be seen as a methodology for enforcing certain known characteristics of turbulence on a conventional mixing model. This is achieved by localising the mixing operation in a reference space. The reference space variables are selected to emulate the properties of a turbulent flow which have a strong effect on reactive quantities. The best and simplest example is an MMC model which has a single reference variable emulating the mixture fraction. In diffusion flames turbulent fluctuations of reacting quantities are strongly correlated with fluctuations of the mixture fraction. By making mixing local in the reference mixture fraction space a CMC-type mixing closure is enforced. In the original interpretation of MMC the reference variables are modelled as Markov processes. Since the reference variables should emulate properties of turbulent flows as realistically as possible the next step, and the basis of generalised MMC, is to remove the Markovian restriction and set reference variables equal to traced Lagrangian quantities within DNS or LES flow fields. Indeed, no Markov value can emulate the mixture fraction better than the mixture fraction itself. (Using a Markov vector process of dimension higher than the number of conditioning variables represents a more economical alternative for producing reference variables in generalised MMC.) The generalised MMC approach effectively incorporates the mixture fraction-based models, the PDF methods and LES/DNS techniques into a single methodology with possibility of blending useful features developed previously for conventional models. The generalised approach to MMC stimulates a more flexible understanding of simulations using sparsely placed Lagrangian particles as tools that may provide accurate joint distributions of reactive scalars at relatively low computational cost. The physical reasoning behind the new interpretation of MMC is supported by example computations for a partially premixed methane/air diffusion flame (Sandia Flame D). The scheme utilises LES for the dynamic field and a sparse-Lagrangian filtered density function method with MMC mixing for the scalar field. Two different particle mixing schemes are tested. Simulations are performed using only 35,000 Lagrangian particles (of these only 10,000 are chemically active) on a single workstation. The relatively low computational cost allows the use of realistic chemical kinetics containing 34 reactive species and 219 reactions.
Keyword Multiple mapping conditioning
Lagrangian simulations
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Fri, 05 Jun 2009, 14:53:26 EST by Siona Saplos on behalf of Research Management Office