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Scalar-dissipation modeling for passive and active scalars: A priori study using direct numerical simulation

Selle, L. C. and Bellan, J. (2007) Scalar-dissipation modeling for passive and active scalars: A priori study using direct numerical simulation. Proceedings of the Combustion Institute, 31 (1). pp. 1665-1673. ISSN 1540-7489.

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Transitional databases from direct numerical simulation (DNS) of three-dimensional mixing layers for single-phase flows and two-phase flows with evaporation are analyzed and used to examine the typical hypothesis that the scalar-dissipation probability distribution function (PDF) may be modeled as a Gaussian. The databases encompass a singlecomponent fuel and four multicomponent fuels, two initial Reynolds numbers (Re), two mass loadings for two-phase flows and two free-stream gas temperatures. Using the DNS-calculated moments of the scalar-dissipation PDF, it is shown, consistent with existing experimental information on single-phase flows, that the Gaussian is a modest approximation of the DNS-extracted PDF, particularly poor in the range of the high scalar-dissipation values, which are significant for turbulent reaction rate modeling in non-premixed flows using flamelet models. With the same DNS-calculated moments of the scalar-dissipation PDF and making a change of variables, a model of this PDF is proposed in the form of the β-PDF which is shown to approximate much better the DNS-extracted PDF, particularly in the regime of the high scalar-dissipation values. Several types of statistical measures are calculated over the ensemble of the 14 databases. For each statistical measure, the proposed β-PDF model is shown to be superior to the Gaussian in approximating the DNS-extracted PDF. Additionally, the agreement between the DNS-extracted PDF and the β-PDF even improves when the comparison is performed for higher initial-Re layers, whereas the comparison with the Gaussian is independent of the initial Re values. For two-phase flows, the comparison between the DNS-extracted PDF and the β-PDF also improves with increasing free-stream gas temperature and mass loading. The higher fidelity approximation of the DNS-extracted PDF by the β-PDF with increasing Re, gas temperature and mass loading bodes well for turbulent reaction rate modeling.

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Additional Information:© 2006 The Combustion Institute. Published by Elsevier Inc. Available online 4 August 2006. This study was conducted at the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech), under the partial sponsorship of the Donors of The Petroleum Research Fund administered by the American Chemical Society through a grant (to J.B.) for Caltech Post Doctoral Fellow (L.S.) support and of the US Department of Energy. Computational resources were provided by the supercomputing facility at JPL.
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American Chemical Society Petroleum Research FundUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:Scalar-dissipation modeling
Record Number:CaltechAUTHORS:20171019-100826494
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Official Citation:L.C. Selle, J. Bellan, Scalar-dissipation modeling for passive and active scalars: A priori study using direct numerical simulation, In Proceedings of the Combustion Institute, Volume 31, Issue 1, 2007, Pages 1665-1673, ISSN 1540-7489, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82484
Deposited By: Tony Diaz
Deposited On:19 Oct 2017 18:12
Last Modified:19 Oct 2017 18:12

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