Effects of Lewis number on turbulent scalar transport and its modelling in turbulent premixed flames
- Engineering Department, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom)
- Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)
The behaviour of the turbulent scalar flux in premixed flames has been studied using Direct Numerical Simulation (DNS) with emphasis on the effects of Lewis number in the context of Reynolds-averaged closure modelling. A database was obtained from DNS of three-dimensional freely propagating statistically planar turbulent premixed flames with simplified chemistry and a range of global Lewis numbers from 0.34 to 1.2. Under the same initial conditions of turbulence, flames with low Lewis numbers are found to exhibit counter-gradient transport, whereas flames with higher Lewis numbers tend to exhibit gradient transport. The Reynolds-averaged transport equation for the turbulent scalar flux is analysed in detail and the performance of existing models for the unclosed terms is assessed with respect to corresponding quantities extracted from DNS data. Based on this assessment, existing models which are able to address the effects of non-unity Lewis number on turbulent scalar flux transport are identified, and new or modified models are suggested wherever necessary. In this way, a complete set of closure models for the scalar flux transport equation is prescribed for use in Reynolds-Averaged Navier-Stokes simulations. (author)
- OSTI ID:
- 21195827
- Journal Information:
- Combustion and Flame, Vol. 156, Issue 7; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
LEWIS NUMBER
NAVIER-STOKES EQUATIONS
SCALARS
SIMULATION
FLAMES
TRANSPORT THEORY
THREE-DIMENSIONAL CALCULATIONS
PERFORMANCE
TURBULENCE
MATHEMATICAL MODELS
COMPARATIVE EVALUATIONS
Turbulent scalar flux
Direct Numerical Simulation
Counter-gradient transport
Reynolds-Averaged Navier-Stokes modelling