Analysis of the development of the flame brush in turbulent premixed spherical flames
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AbstractThe thickness of the turbulent flame brush is central to the modeling of premixed turbulent combustion and the theory of turbulent diffusion is often applied to explain the growth of the brush with varying success. However, numerous studies have shown that the brush evolves differently from the dispersion of material points on the account of flame propagation, density changes across the front, and hydrodynamic instabilities. Modifications to turbulent diffusion theory to incorporate these effects are challenging since the theory is Lagrangian. In this article, we present an alternate Eulerian framework based on the surface density formalism. We employ the proposed framework to analyze a database of direct numerical simulations of spherical turbulent premixed flames in decaying isotropic turbulence and recover mechanisms for which scaling laws are proposed and assessed against data. We characterize quantitatively two mechanisms: one related to the mean velocity gradient induced by thermal expansion and the other due to flame propagation in the presence of curvature. We demonstrate that the net effect of these two processes is to hinder the growth of the turbulent flame brush in the present configuration. Our analysis supports the notion that the turbulent flame brush does not grow indefinitely, rather it attains a maximum thickness.
CitationKulkarni, T., & Bisetti, F. (2021). Analysis of the development of the flame brush in turbulent premixed spherical flames. Combustion and Flame, 234, 111640. doi:10.1016/j.combustflame.2021.111640
SponsorsThis work was supported by the National Science Foundation [grant number 1805921]. Numerical simulations were carried out on the “Shaheen” supercomputer at King Abdullah University of Science and Technology (KAUST); and on the “Stampede2” supercomputer at the Texas Advanced Computing Center (TACC) through allocation TG-CTS180002 under the Extreme Science and Engineering Discovery Environment (XSEDE).
JournalCombustion and Flame