• Title/Summary/Keyword: Countergradient Turbulent Flux

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First Moment Closure Simulation of Floating Turbulent Premixed Flames in Stagnation Flows (정체 유동장에 떠있는 난류 예혼합 화염의 일차 모멘트 닫힘 모사)

  • Lee, Eun-Ju;Huh, Kang-Y.
    • 한국연소학회:학술대회논문집
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    • 2000.05a
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    • pp.122-132
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    • 2000
  • Computational fluid dynamic simulation is performed for the floating turbulent premixed flames stabilized in stagnation flows of Cho et al. [1] and Cheng and Shepherd [2]. They are both in the wrinkled flamelet regime far from the extinction limit with $u'/S^{0}_{L}$ less than unity. The turbulent flux is given in the first moment closure as a sum of the classical gradient flux due to turbulent motions and the countergradient flux due to thermal expansion. The parameter $N_{B}'s$ are greater than unity with the countergradient flux dominant over the gradient flux. The countergradient flux is assumed to be zero in $\bar{c}<0.05$. The flame surface density is modeled as a symmetric parabolic function with respect to $\bar{c}$. The product of the maximum flame surface density and the mean stretch factor is considered as a tuning constant to match the flame location. Good agreement is achieved with the measured $\tilde{w}$ and $\bar{c}$ profiles along the axis in both flames.

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