Accounting for the fluctuations of the scalar dissipation rate (x) in modeling nonpremixed and partially premixed combustion processes can be crucial. However, the dissipation rate can never be fully resolved in the CFD (RANS or LES) of practical, engineering applications due to their high Reynolds numbers. That the local, instantaneous dissipation rate is of leading-order importance in turbulent combustion is made explicit by flamelet modeling. Formulations which account for fluctuations of X in Lagrangian probability density function (pdf) transport models also exist. Moment methods, like conditional moment closure (CMC) modeling, are the least computationally burdensome of the state-of-theart combustion modeling approaches, but have yet to incorporate fluctuations of x in a computationally efficient manner. Here a simple extension of CMC has been formulated which accounts for local, unresolved flame structures and which does not add significantly to the computational overhead of CMC under the current closure strategies. As a moment method, the model can be readily coupled to popular commercial CFD codes.
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