Modelling a turbulent premixed flame series using an MMC-LES model with a flow-adapted flame wrinkling closure

Abstract

Multiple Mapping Conditioning-Large Eddy Simulation (MMC-LES) with a shadow-position reference variable to localise scalar mixing is used to model a series of premixed flames in the thin reaction zones regime. A flame wrinkling closure based on resolved velocity and length scales is introduced for the primary model parameter, λ, which determines the effective diffusion and flame propagation speed in shadow-position space. Additionally, a mixing timescale, τ, is introduced which accounts for the effects of reaction-induced steepening of reactive scalar gradients on dissipation. Relative to existing versions of the premixed MMC-LES model with constant λ and τ based on passive scalar turbulent characteristics, the enhanced model yields much-improved prediction of flame propagation for the entire flame series without the need for parameter tuning and unphysical changes in the inner flame structure. Predictions of mean major and minor reactive species profiles are also satisfactory. The developed approach is relevant for a broad range of premixed flames and is currently being tested for cases in the distributed regime.