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Detailed characteristics of drop-laden mixing layers: Large eddy simulation predictions compared to direct numerical simulation

Okong'o, Nora and Leboissetier, Anthony and Bellan, Josette (2008) Detailed characteristics of drop-laden mixing layers: Large eddy simulation predictions compared to direct numerical simulation. Physics of Fluids, 20 (10). Art. No. 103305. ISSN 1070-6631. doi:10.1063/1.2990758.

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Results are compared from direct numerical simulation (DNS) and large eddy simulation (LES) of a temporal mixing layer laden with evaporating drops to assess the ability of LES to reproduce detailed characteristics of DNS. The LES used computational drops, each of which represented eight physical drops, and a reduced flow field resolution using a grid spacing four times larger than that of the DNS. The LES also used models for the filtered source terms, which express the coupling of the drops with the flow, and for the unresolved subgrid-scale (SGS) fluxes of species mass, momentum, and enthalpy. The LESs were conducted using one of three different SGS-flux models: dynamic-coefficient gradient (GRD), dynamic-coefficient Smagorinsky (SMD), and constant-coefficient scale similarity (SSC). The comparison of the LES with the filtered-and-coarsened (FC) DNS considered detailed aspects of the flow that are of interest in ignition or full combustion. All LESs captured the largest-scale vortex, the global amount of vapor emanating from the drops, and the overall size distribution of the drops. All LESs tended to underpredict the global amount of irreversible entropy production (dissipation). The SMD model was found unable to capture either the global or local vorticity variation and had minimal small-scale activity in dynamic and thermodynamic variables compared to the FC-DNS. The SMD model was also deficient in predicting the spatial distribution of drops and of the dissipation. In contrast, the GRD and SSC models did mimic the small-scale activity of the FC-DNS and the spatial distribution of drops and of the dissipation. Therefore, the GRD and SSC models are recommended, while the SMD model seems inappropriate for combustion or other problems where the local activity must be predicted.

Item Type:Article
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Bellan, Josette0000-0001-9218-7017
Additional Information:© 2008 American Institute of Physics. Received 20 February 2008; accepted 21 July 2008; published 28 October 2008. This study was conducted at the Jet Propulsion Laboratory (JPL) of the California Institute of Technology (Caltech) under the sponsorship of the U.S. Department of Energy, with R. Danz and D. Hooker serving as contract monitors, under an agreement with the National Aeronautics and Space Administration. Computations were performed on the SGI Origin 2000 at the JPL Supercomputing Center.
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Department of EnergyUNSPECIFIED
Subject Keywords:drops, enthalpy, entropy, flow simulation, mixing
Issue or Number:10
Record Number:CaltechAUTHORS:OKOpof08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12281
Deposited By: Archive Administrator
Deposited On:03 Nov 2008 22:57
Last Modified:08 Nov 2021 22:27

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