The Matalon–Matkowsky–Clavin–Joulin theory or MMCJ theory refers to a longwave hydrodynamic model of a premixed flame with a large-amplitude flame wrinkling, developed independently by Moshe Matalon & Bernard J. Matkowsky and Paul Clavin & Guy Joulin, following the pioneering study by Paul Clavin and Forman A. Williams, Pierre Pelcé and Paul Clavin and by Gregory Sivashinsky. The theory, for the first time, calculated the burning rate of the curved flame that differs from the burning rate of the planar flame due to flame stretch, associated with the flame curvature and the strain imposed on the flame by the flow field. Specifically, the theory unraveled two important results
The usual Rankine–Hugoniot conditions, applicable across the flame, gets a correction due to the inner structure of the premixed flame. The burning-rate of the flame is influenced by the intrinsic curvature (seen by an observer moving with the flame) and tangential straining of the flame due to flow non-uniformities.
Corrections to the interfacial conditions
Kinematic condition and the burning rate formula The kinematic condition, i.e., G equation, at the flame interface is given by
∂ G ∂ t + v − ⋅ ∇ G = S T | ∇ G | . {\displaystyle {\frac {\partial G}{\partial t}}+\mathbf {v} ^{-}\cdot \nabla G=S_{T}|\nabla G|.}
where n = ∇ G / | ∇ G | {\displaystyle \mathbf {n} =\nabla G/|\nabla G|} is the unit normal to the flame surface (pointing towards the burnt gas side), v {\displaystyle \mathbf {v} } is the flow velocity field evaluated at the flame surface. According to Matalon–Matkowsky–Clavin–Joulin theory, if S L {\displaystyle S_{L}} and δ L {\displaystyle \delta _{L}} are the laminar burning speed and thickness of a planar flame (and τ L = δ L / S L {\displaystyle \tau _{L}=\delta _{L}/S_{L}} be the corresponding flame residence time), then the burning speed S T {\displaystyle S_{T}} for the curved flame with respect to the unburnt gas is given by
S T = S L + M c δ L ( S L − v − ⋅ n ) ∇ ⋅ n − M t δ L ∇ t ⋅ v t − {\displaystyle {\begin{aligned}S_{T}=S_{L}+{\mathcal {M}}_{c}\delta _{L}(S_{L}-\mathbf {v} ^{-}\cdot \mathbf {n} )\nabla \cdot \mathbf {n} -{\mathcal {M}}_{t}\delta _{L}\nabla _{t}\cdot \mathbf {v} _{t}^{-}\end{aligned}}}
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