An analysis of premixed flamelet models for large eddy simulation of turbulent combustion

Abstract

When premixed flamelet models are applied in the context of large eddy simulation, a number of assumptions are implicity made. The validity of these assumptions depends on, for example, the simulated flame’s location within the premixed regime diagram, the accuracy of the presumed subfilter flamelet coordinate distributions, and the extent to which the asymptotic flamelets capture the turbulence-perturbed chemistry. Here, the errors that arise due to these assumptions are considered, analyzed, and compared using a direct numerical simulation of a premixed turbulent flame propagating in the thin reaction zones regime. Flamelet representations of the progress variable source term are formed in an a priori fashion. Level set flamelet methods in particular are considered because, although they offer a number of advantages, they make some of the most stringent flame structure assumptions. Errors due to the level set model are evaluated relative to other flamelet error sources, such as the shape of the presumed probability density function and the influence of the variance model. The results provide guidance on the importance of the individual modeling assumptions, and are used to propose a new modeling strategy in an effort to improve the level set framework.