Pocket formation and the flame surface density equation

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Description

The occurrence and properties of singularities in the equation for the surface density function {sigma} {triple_bond}{vert_bar}{del}{Phi}{vert_bar} are analyzed analytically and numerically using data from two dimensional direct numerical simulation (DNS) of pocket formation in a premixed methane-air flame. The various stages and the relevant time scales associated with pocket formation were determined in a previous study. It was found that isolated pockets form if and only if a nondegenerate critical point of a saddle point type appears. The appearance of a singularity in the isoline representing the flame front may have implications to modeling of the terms in the surface ... continued below

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19 p.

Creation Information

Kollman, W. & Chen, J.H. March 1, 1998.

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Authors

  • Kollman, W. Univ. of California, Davis, CA (United States)
  • Chen, J.H. Sandia National Labs., Livermore, CA (United States). Combustion Research Facility

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Livermore, CA (United States)
    Place of Publication: Livermore, California

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Description

The occurrence and properties of singularities in the equation for the surface density function {sigma} {triple_bond}{vert_bar}{del}{Phi}{vert_bar} are analyzed analytically and numerically using data from two dimensional direct numerical simulation (DNS) of pocket formation in a premixed methane-air flame. The various stages and the relevant time scales associated with pocket formation were determined in a previous study. It was found that isolated pockets form if and only if a nondegenerate critical point of a saddle point type appears. The appearance of a singularity in the isoline representing the flame front may have implications to modeling of the terms in the surface density function (sdf) approach during such transient events as pocket formation. The sink and source terms in sdf are evaluated in the neighborhood of a critical point using DNS data during pocket formation, and an analytic representation of a scalar in the vicinity of the critical point which allows for the computation of all kinematic properties. The analytic and computational results show that the normal restoration and dissipation terms in the sdf become singular at the critical point when the pocket emerges. Furthermore, the analytic results show that the singularities exactly cancel, and therefore, the main conclusion is that it is unnecessary to model the singular behavior of these terms at critical points. However, closure of their sum is recommended.

Physical Description

19 p.

Notes

OSTI as DE98052541

Source

  • 27. international symposium on combustion, Boulder, CO (United States), 2-7 Aug 1998

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  • Other: DE98052541
  • Report No.: SAND--98-8472C
  • Report No.: CONF-980804--
  • Grant Number: AC04-94AL85000
  • DOI: 10.2172/658164 | External Link
  • Office of Scientific & Technical Information Report Number: 658164
  • Archival Resource Key: ark:/67531/metadc712568

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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Creation Date

  • March 1, 1998

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

Description Last Updated

  • April 12, 2016, 8:20 p.m.

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Kollman, W. & Chen, J.H. Pocket formation and the flame surface density equation, report, March 1, 1998; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc712568/: accessed September 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.