A Consistent Level Set Formulation for Large-Eddy Simulation of Premixed Turbulent Combustion
نویسنده
چکیده
A consistent formulation of the G-equation approach for LES is developed. The unfiltered G-equation is valid only at the instantaneous flame front location. Hence, in a filtering procedure applied to derive the appropriate LES equation, only the instantaneous unfiltered flame surface can be considered. A new filter kernel is provided, which averages along the flame surface. The filter kernel is used to derive the G-equation for the filtered flame front location. This equation has two unclosed terms, involving a flame front conditional averaged flow velocity, and a filtered propagation term. A model for the conditional velocity is derived, expressing this quantity in terms of the Favre-filtered flow velocity, which is typically known from a flow solver. This model leads to the appearance of a density ratio in the propagation term of the G-equation. LES of combustion in the thin reaction zones regime is discussed in the LES regime diagram. A new line is identified separating the thin reaction zones regime into two parts, where the broadended flame thickness is larger and smaller than the filter size, respectively. A model for the propagation term is provided. This leads to a term including the sub-filter turbulent burning velocity and an additional term proportional to the resolved flame front curvature. For the former, an algebraic model is provided from an equation for the sub-filter flame front wrinkling. The latter term depends on the inverse of the sub-filter Damköhler number and disappears in the corrugated flamelets regime.
منابع مشابه
Large-Eddy Simulation of Turbulent Combustion
In recent years, Large Eddy Simulation (LES) has been successfully applied to non-premixed and premixed turbulent combustion problems [1, 2, 3]. In most technical combustion applications, the pure non-premixed or premixed combustion models are no longer valid, since partially premixed combustion has to be taken into account. An example is the stabilization region of a lifted non-premixed flame....
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