Combustion and Flame, Vol.199, 183-193, 2019
A hybrid flamelet finite-rate chemistry approach for efficient LES with a transported FDF
A hybrid method combining flamelet tabulation with transported filtered density function (FDF) finite rate chemistry has been developed and applied to large eddy simulation (LES) of the Sydney/Sandia piloted turbulent flame with inhomogeneous inlets. Aiming to improve the efficiency while maintaining accuracy, the hybrid method applies the computationally expensive Lagrangian particles representing FDF transport and direct chemistry only in selected, dynamically varying locations. The rest of the domain is treated with flamelet chemistry based on the Eulerian fields and a presumed top-hat PDF closure. The method relies on consistency between Eulerian and Lagrangian fields through robust, accurate coupling and consistent modeling. The performance of the hybrid model is verified by an extensive comparison against the experiment and the 'pure' models, i.e., the (a) flamelet LES with presumed FDF, (b) flamelet LES with transported FDF, and (c) direct chemistry LES with transported FDF. Finite rate chemistry is found to improve species predictions over flamelet chemistry and the hybrid method is found to reproduce these improvements by using particles with finite rate chemistry only at locations where the flamelet is not sufficient, promising a reduced computational cost. (C) 2018 Published by Elsevier Inc. on behalf of The Combustion Institute.