Assessment of flamelet manifolds for turbulent flame-wall interactions in Large-Eddy Simulations

Abstract

A turbulent side-wall quenching (SWQ) flame in a fully developed channel flow is studied using Large-Eddy Simulation (LES) with a tabulated chemistry approach. Three different flamelet manifolds with increasing levels of complexity are applied: the Flamelet-Generated Manifold (FGM) considering varying enthalpy levels, the Quenching Flamelet-Generated Manifold (QFM), and the recently proposed Quenching Flamelet-Generated Manifold with Exhaust Gas Recirculation (QFM-EGR), with the purpose being to assess their capability to predict turbulent flame-wall interactions (FWIs), which are highly relevant to numerical simulations of real devices such as gas turbines and internal combustion engines. The accuracy of the three manifolds is evaluated and compared a posteriori, using the data from a previously published flame-resolved simulation with detailed chemistry for reference. For LES with the FGM, the main characteristics such as the mean flow field, temperature, and major species can be captured well, while notable deviations from the reference results are observed for the near-wall region, especially for pollutant species such as \ce{CO}. In accordance with the findings from laminar FWI, improvement is also observed in the simulation with QFM under turbulent flow conditions. Although LES with the QFM-EGR shows a similar performance in the prediction of mean quantities as LES with QFM, it presents significantly better agreement with the reference data regarding instantaneous thermo-chemical states near the quenching point. This indicates the necessity to take into account the mixing effects in the flamelet manifold to correctly capture the flame-vortex interaction near the flame tip in turbulent configurations. Based on the findings from this study, suitable flamelet manifolds can be chosen depending on the aspects of interest in practical applications.