A comparative study of presumed PDFs for premixed turbulent combustion modeling based on progress variable and its variance

Premixed turbulent combustion simulations often use flamelets (1-D laminar flame solutions) and presumed probability density functions (PDF) for modeling turbulence chemistry interaction. The flamelets can also be spatially filtered at multiple length scales to directly tabulate a PDF integrated manifold. Similar to the presumed PDF approach using β-function, the turbulent chemistry is tabulated using two controlling variables: progress variable and its subgrid variance. The performance of manifolds constructed from a premixed flamelet using: β-PDF, spatial filtering at multiple length scales and spatial filtering only at grid scale are compared a priori and a posteriori. Computation of the progress variable subgrid variance is investigated using static as well as dynamic algebraic mixing models. A Direct Numerical Simulation (DNS) database of a turbulent Bunsen flame is used for a priori and a posteriori investigation of the PDFs and the algebraic models. It is observed that algebraic models lead to correct predictions at filter widths smaller than the laminar flame thickness while deviations occur at larger filter widths. A posteriori the manifolds exhibit similar performance on account of the deviation in subgrid variance prediction from the algebraic models. However, the multi filtered flamelet model clearly exhibits a superior a priori performance and needs to be investigated further.