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A new multiple mapping conditioning model with a shadow position reference variable for localising mixing is implemented in a large eddy simulation solver and validated against three experimental turbulent premixed flames. The shadow position used here has diffusion coefficient which is linked to the turbulent propagation speed. Localisation of mixing produces a flamelet-like inner structure in shadow position space and the structure in physical space is determined by the subgrid dispersion of shadow and physical positions. The lengths of the predicted flames match the trends observed for the experimental flames, and the predicted inner structures are consistent with what is expected for these flames in the thin reaction zones regime. The statistical predictions are in very good quantitative agreement with the experimental data for velocity and major species. Errors for reaction progress variable, turbulent kinetic energy and minor species (carbon monoxide) are generally larger yet mostly within the ranges reported in the literature. [ABSTRACT FROM AUTHOR]

Abstract: The present work suggests a theory of reverse combustion linking (RCL). RCL is a central unit operation of underground coal gasification (UCG) technology. The theory is based on analyzing the stability of different branches of the propagation speed curves and determining the regime that is responsible for propagation of the flame during RCL. The theory is in good qualitative and quantitative agreement with the data obtained in practical use of RCL in UCG operations. [Copyright &y& Elsevier]

Abstract: The rate of generation of fluctuations with respect to the scalar values conditioned on the mixture fraction, which significantly affects turbulent nonpremixed combustion processes, is examined. Simulation of the rate in a major mixing model is investigated and the derived equations can assist in selecting the model parameters so that the level of conditional fluctuations is better reproduced by the models. A more general formulation of the multiple mapping conditioning (MMC) model that distinguishes the reference and conditioning variables is suggested. This formulation can be viewed as a methodology of enforcing certain desired conditional properties onto conventional mixing models. Examples of constructing consistent MMC models with dissipation and velocity conditioning as well as of combining MMC with large eddy simulations (LES) are also provided. [Copyright &y& Elsevier]

Obtains the exact unclosed equation for the phase-space density function in turbulent flows using conditional techniques. Implications for stochastic Lagrangian models based on the assumption of similarity with a Markov process; Analysis of the random particle sources problem; Significance of the Fokker-Planck equation on the Lagrangian phase-space density function.