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Effects of Lewis number on Flame Surface Density transport in turbulent premixed combustion

Lookup NU author(s): Professor Nilanjan ChakrabortyORCiD



The transport of flame surface density (FSD) in turbulent premixed flames has been studied using a database obtained from Direct Numerical Simulation (DNS). Three-dimensional freely propagating developing statistically planar turbulent premixed flames have been examined over a range of global Lewis numbers from 0.6 to 1.2. Simplified chemistry has been used and the emphasis is on the effects of Lewis number on FSD transport in the context of Reynolds-averaged closure modelling. Under the same initial conditions of turbulence, flames with low Lewis numbers are found to exhibit counter-gradient transport of FSD, whereas flames with higher Lewis numbers tend to exhibit gradient transport of FSD. Stronger heat release effects for lower Lewis number flames are found to lead to an increase in the positive (negative) value of the dilatation rate (normal strain rate) term in the FSD transport equation with decreasing Lewis number. The contribution of flame curvature to FSD transport is found to be influenced significantly by the effects of Lewis number on the curvature dependence of the magnitude of the reaction progress variable gradient, and on the combined reaction and normal diffusion components of displacement speed. The modelling of the various terms of the FSD transport equation has been analysed in detail and the performance of existing models is assessed with respect to the terms assembled from corresponding quantities extracted from DNS data. Based on this assessment, suitable models are identified which are able to address the effects of non-unity Lewis number on FSD transport, and new or modified models are suggested wherever necessary.

Publication metadata

Author(s): Chakraborty N, Cant RS

Publication type: Article

Publication status: Published

Journal: Combustion and Flame

Year: 2011

Volume: 158

Issue: 9

Pages: 1768-1787

Print publication date: 16/02/2011

Date deposited: 12/10/2011

ISSN (print): 0010-2180

ISSN (electronic): 1556-2921

Publisher: Elsevier Inc


DOI: 10.1016/j.combustflame.2011.01.011


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