A Comparison of Flamelet LES Models for Premixed Turbulent Combustion

Abstract

While Large Eddy Simulations (LES) has reached some degree of maturity for non-reacting flows, its application to reacting flows is still being developed and different modeling approaches have been proposed. Typically, the characteristic scales where the chemical reactions take place are usually far below the affordable mesh resolution, and the combustion process has to be modeled at the subgrid level. At present, it is not evident which approach is the best – all available methods, from the classical BML model to the most sophisticated Linear Eddy model have merits and demerits – and here we focus on the flamelet approach based on a filtered reaction coordinate. The flamelet approach is of interest mainly because of its rather low computational cost and versatility in comparison to the other available methods. The objective of this study is to compare different premixed turbulent flamelet models, and in particular we examine a propagation-based flamelet model and a filtered flamelet model, using different sub-models for the flame wrinkling. This investigation is primarily based on numerical simulations of flame kernel growth in fully developed turbulence and a bluff body stabilized flame, and comparisons are made with experimental data for validation and comparison. Besides using the same thermodynamic model, the same code, grids and initial as well as boundary conditions are used. Both models appear to give reasonable results, the filtered flamelet model being more sensitive to the relative resolution.