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DNS and LES of a Shear-Free Mixing LayerThe purpose of this work is twofold. First, given the computational resources available today, it is possible to reach, using DNS, higher Reynolds numbers than in Briggs et al.. In the present study, the microscale Reynolds numbers reached in the low- and high-energy homogeneous regions are, respectively, 32 and 69. The results reported earlier can thus be complemented and their robustness in the presence of increased turbulence studied. The second aim of this work is to perform a detailed and documented LES of the shear-free mixing layer. In that respect, the creation of a DNS database at higher Reynolds number is necessary in order to make meaningful LES assessments. From the point of view of LES, the shear-free mixing-layer is interesting since it allows one to test how traditional LES models perform in the presence of an inhomogeneity without having to deal with difficult numerical issues. Indeed, as argued in Briggs et al., it is possible to use a spectral code to study the shear-free mixing layer and one can thus focus on the accuracy of the modelling while avoiding contamination of the results by commutation errors etc. This paper is organized as follows. First we detail the initialization procedure used in the simulation. Since the flow is not statistically stationary, this initialization procedure has a fairly strong influence on the evolution. Although we will focus here on the shear-free mixing layer, the method proposed in the present work can easily be used for other flows with one inhomogeneous direction. The next section of the article is devoted to the description of the DNS. All the relevant parameters are listed and comparison with the Veeravalli & Warhaft experiment is performed. The section on the LES of the shear-free mixing layer follows. A detailed comparison between the filtered DNS data and the LES predictions is presented. It is shown that simple eddy viscosity models perform very well for the present test case, most probably because the flow seems to be almost isotropic in the small-scale range that is not resolved by the LES.
Document ID
20040034211
Acquisition Source
Headquarters
Document Type
Other
Authors
Knaepen, B. (Stanford Univ. Stanford, CA, United States)
Debliquy, O. (Free Univ. Brussels, Belgium)
Carati, D. (Free Univ. Brussels, Belgium)
Date Acquired
September 7, 2013
Publication Date
January 1, 2003
Publication Information
Publication: Center for Turbulence Research Annual Research Briefs 2003
Subject Category
Fluid Mechanics And Thermodynamics
Funding Number(s)
CONTRACT_GRANT: NCC2-1371
CONTRACT_GRANT: ARC-02/07-283
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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