Interplay between background turbulence and Darrieus-Landau instability in premixed flames via a model equation
Fogla, Navin
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https://hdl.handle.net/2142/16182
Description
Title
Interplay between background turbulence and Darrieus-Landau instability in premixed flames via a model equation
Author(s)
Fogla, Navin
Issue Date
2010-05-19T18:40:00Z
Director of Research (if dissertation) or Advisor (if thesis)
Matalon, Moshe
Department of Study
Mechanical Sci & Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Michelson Sivashinsky equation
Darrieus–Landau instability
turbulent flames
self-fractalization
Abstract
The effect of the Darrrieus Landau instability on a premixed flame in a turbulent environment is investigated using a model equation known as the Michelson Sivashinsky equation, in both one and two dimensions. The equation is externally forced with noise representative of weak turbulence in the flow and the response of
the flame to both unstructured and structured noise is examined. It is found that for a given noise intensity there exists a threshold domain size, beyond which the instability amplifies the perturbations due to noise
and causes the formation of wrinkles on the flame surface, leading to an increase in the propagation velocity. Scaling laws are proposed for the increase in propagation velocity with variations in noise intensity and a
bifurcation parameter, which includes the effects of parameters such as the domain size, equivalence ratio
and reaction rates. Self fractalization of the flame is observed at high noise intensities. Effects of the scale
of noise, analogous to the scale of turbulence, are also examined and a resonant behavior is found to exist at certain scales. In the two dimensional case, cellular structures, similar to the ones observed experimentally
on expanding spherical flames, are observed on the flame surface. Scaling laws similar to the one dimensional case are proposed.
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