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Journal of Combustion
Volume 2011, Article ID 628208, 13 pages
http://dx.doi.org/10.1155/2011/628208
Research Article

Statistics of Conditional Fluid Velocity in the Corrugated Flamelets Regime of Turbulent Premixed Combustion: A Direct Numerical Simulation Study

1School of Mechanical and System Engineering, Newcastle University, Claremont Road, Newcastle-upon-tyne NE1 7RU, UK
2Department of Applied Mechanics, Chalmers University of Technology, 412 96, Gothenberg, Sweden

Received 13 February 2011; Revised 23 April 2011; Accepted 8 June 2011

Academic Editor: Vladimir A. Sabel

Copyright © 2011 Nilanjan Chakraborty and Andrei N. Lipatnikov. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The statistics of mean fluid velocity components conditional in unburned reactants and fully burned products in the context of Reynolds Averaged Navier Stokes (RANS) simulations have been studied using a Direct Numerical Simulation database of statistically planar turbulent premixed flame representing the corrugated flamelets regime combustion. Expressions for conditional mean velocity and conditional velocity correlations which are derived based on a presumed bimodal probability density function of reaction progress variable for unity Lewis number flames are assessed in this study with respect to the corresponding quantities extracted from DNS data. In particular, conditional surface averaged velocities (𝑢𝑖)𝑅𝑠 and the velocity correlations (𝑢𝑖𝑢𝑗)𝑅𝑠 in the unburned reactants are demonstrated to be effectively modelled by the unconditional velocities (𝑢𝑖)𝑅 and velocity correlations (𝑢𝑖𝑢𝑗)𝑅, respectively, for the major part of turbulent flame brush with the exception of the leading edge. By contrast, conditional surface averaged velocities (𝑢𝑖)𝑃𝑠 and the velocity correlations (𝑢𝑖𝑢𝑗)𝑃𝑠 in fully burned products are shown to be markedly different from the unconditional velocities (𝑢𝑖)𝑃 and velocity correlations (𝑢𝑖𝑢𝑗)𝑃, respectively.