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Consistent large-eddy simulation of a temporal mixing layer laden with evaporating drops. Part 2. A posteriori modelling

Leboissetier, Anthony and Okong'o, Nora and Bellan, Josette (2005) Consistent large-eddy simulation of a temporal mixing layer laden with evaporating drops. Part 2. A posteriori modelling. Journal of Fluid Mechanics, 523 . pp. 37-78. ISSN 0022-1120. doi:10.1017/S0022112004002101.

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Large-eddy simulation (LES) is conducted of a three-dimensional temporal mixing layer whose lower stream is initially laden with liquid drops which may evaporate during the simulation. The gas-phase equations are written in an Eulerian frame for two perfect gas species (carrier gas and vapour emanating from the drops), while the liquid-phase equations are written in a Lagrangian frame. The effect of drop evaporation on the gas phase is considered through mass, species, momentum and energy source terms. The drop evolution is modelled using physical drops, or using computational drops to represent the physical drops. Simulations are performed using various LES models previously assessed on a database obtained from direct numerical simulations (DNS). These LES models are for: (i) the subgrid-scale (SGS) fluxes and (ii) the filtered source terms (FSTs) based on computational drops. The LES, which are compared to filtered-and-coarsened (FC) DNS results at the coarser LES grid, are conducted with 64 times fewer grid points than the DNS, and up to 64 times fewer computational than physical drops. It is found that both constant-coefficient and dynamic Smagorinsky SGS-flux models, though numerically stable, are overly dissipative and damp generated small-resolved-scale (SRS) turbulent structures. Although the global growth and mixing predictions of LES using Smagorinsky models are in good agreement with the FC-DNS, the spatial distributions of the drops differ significantly. In contrast, the constant-coefficient scale-similarity model and the dynamic gradient model perform well in predicting most flow features, with the latter model having the advantage of not requiring a priori calibration of the model coefficient. The ability of the dynamic models to determine the model coefficient during LES is found to be essential since the constant-coefficient gradient model, although more accurate than the Smagorinsky model, is not consistently numerically stable despite using DNS-calibrated coefficients. With accurate SGS-flux models, namely scale-similarity and dynamic gradient, the FST model allows up to a 32-fold reduction in computational drops compared to the number of physical drops, without degradation of accuracy; a 64-fold reduction leads to a slight decrease in accuracy.

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Bellan, Josette0000-0001-9218-7017
Additional Information:© 2005 Cambridge University Press. Received 26 January 2004 and in revised form 24 August 2004. Published online: 21 January 2005. This work was conducted at the Jet Propulsion Laboratory (JPL) of the California Institute of Technology, and was sponsored by the US Department of Energy (contract monitors were R. Danz, Headquarters and D. Hooker, Golden Center) under an agreement with the National Aeronautics and Space Administration. Computations were performed on the SGI Origin2000 at the JPL Supercomputing Center.
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Department of Energy (DOE)UNSPECIFIED
Record Number:CaltechAUTHORS:20171023-152421976
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Official Citation:LEBOISSETIER, A., OKONG'O, N., & BELLAN, J. (2005). Consistent large-eddy simulation of a temporal mixing layer laden with evaporating drops. Part 2. A posteriori modelling. Journal of Fluid Mechanics, 523, 37-78. doi:10.1017/S0022112004002101
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82596
Deposited By: Tony Diaz
Deposited On:24 Oct 2017 20:47
Last Modified:15 Nov 2021 19:51

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