Coupling of simplified chemistry with mixing processes in PDF simulations of turbulent flames

Numerical simulation of turbulent reacting flow is still a challenging task. For the efficient computational simulation and applicability for technical systems, simplifications for both chemistry and turbulence are needed. However, both simplifications are typically treated separately, without considering the coupling between them. In manifold based simplified chemical models, it is assumed that the full thermokinetic state is restricted to slow manifolds, while the turbulent mixing processes pull the states off the manifold. We derive a strategy based on the Global Quasi-linearization (GQL) that allows an efficient coupling of manifold based reduction methods with mixing models in transported Probability Density Function (PDF) models for turbulent reacting flows. The GQL approach identifies a suitable choice of the reaction progress variables which allows a direct application of the mixing models on the reduced variables without having to perform mixing in the full state space and back relaxation to the manifold. To test the validity of the reduced variable, it has been applied for PDF-modeling of a turbulent flame. For the turbulent flame with strong turbulence-reaction interaction, the local-extinction and re-ignition can be captured very well.