LES of a Non-Premixed Flame Using an Extended Flamelet/Progress Variable Model

In previous a priori studies we have examined the flamelet/progress variable model proposed by Pierce and Moin and identified the most important areas for model improvements. The flamelet/progress variable approach is a conserved scalar based model for non-premixed combustion and uses a reactive scalar as an additional parameter in a table lookup. One of the main assumptions in this model is the use of a delta function as a presumed probability density function (PDF) for this reactive scalar. We have previously shown that the use of the beta function provides some improvement. Here, the statistically most-likely distribution is proposed as a presumed PDF for the flamelet parameter. This provides two advantages. First of all, the function depends on a chemical time-scale, and in addition, an arbitrary number of moments can be enforced. The model is applied to flames D and E of the Sandia piloted turbulent jet flame series and results are compared with experimental data.