Publication: “Large Eddy Simulation of scalar transport in turbulent premixed flames

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Title “Large Eddy Simulation of scalar transport in turbulent premixed flames
Authors/Editors* S Tullis, RS Cant
Where published* The Combustion Institute / Canadian Section
How published* Proceedings
Year* 2005
A physically realistic and computationally inexpensive algebraic model for the SGS scalar flux that includes both dilatation driven counter-gradient transport and turbulence driven gradient transport is developed. The counter-gradient model is based on the Bray-Moss- Libby formulation [1,2], and includes the effect of SGS flame wrinkling which depends on the LES filter size. Two modifications to the basic formulation are required: one to account for the effect of LES resolution of the flame interior and a second to account for the spreading of the velocity jump across the flame over the width of the flame brush. The gradient transport model is based on an traditional eddy viscosity approach using the resolved flame tangential strain rate as a proxy for upstream turbulence. The model is analysed using a priori LES where direct numerical simulation (DNS) results (some obtained from previous simulations and others calculated here) were filtered and the models compared directly with the terms as determined using the available SGS information. The DNS data-sets are over a range of heat releases and turbulence intensities and exhibit different mixes of counter-gradient and gradient transport. Good agreement is found between model and DNS, and some interesting observations are made concerning the origins of counter-gradient transport and the ability of LES to capture the phenomenon.
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