Lifetimes of flame balls dragged by model turbulent flows: Role of velocity gradient fluctuations

Yves D’Angelo and Guy Joulin
Phys. Rev. E 69, 036304 – Published 25 March 2004
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Abstract

An isolated combustion spot—known as a flame ball (FB)—is considered while it is advected by a turbulent flow of a lean premixture of such a light fuel as hydrogen. A Batchelor approximation for the surrounding Lagrangian flow is made. This in principle gives one an access to the FB lifetime tlife and to its response to the ambiant Lagrangian rate-of-strain tensor g(t), by means of a nonlinear and forced integro-differential equation for the current FB radius. For a diagonal g(t) deduced from random Markov processes of the Ornstein-Uhlenbeck type, or linearly filtered versions thereof, extensive numerical simulations and approximate theoretical analyses agree that (i) flame balls can definitely live for much longer than their time of spontaneous expansion/collapse; (ii) large enough values of tlife are compatible with Poisson statistics; (iii) the variations of tlife with the characteristics of g(t) mirror the latter’s statistics, more precisely that of trace(g2). Open problems, dealing with a nondiagonal g(t), ignition-related transients and/or collective effects, finally are evoked.

  • Received 1 October 2003

DOI:https://doi.org/10.1103/PhysRevE.69.036304

©2004 American Physical Society

Authors & Affiliations

Yves D’Angelo and Guy Joulin*

  • Laboratoire de Combustion et de Détonique, UPR 9028 du CNRS, ENSMA, 86960 Poitiers, France

  • *Electronic address: dangelo@lcd.ensma.fr

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Vol. 69, Iss. 3 — March 2004

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