Turbulent Premixed Flame Annihilation and Manifold-Based Models

In premixed combustion, manifold-based models project the thermochemical state onto a one-dimensional space in progress variable, a scalar advancing from unburned reactants to products at thermodynamic equilibrium. Under conditions where turbulence intensity is high and the length scales of turbulence are small (comparable to the flame thickness), the curvature of the flame increases until the shape is so corrugated that it may interact with itself. These flame-flame interactions are important for flame propagation as a principal mechanism of local extinction and continuous annihilation of turbulent flame surfaces. Whether these interactions can be captured by a manifold-based model remains an open question since the flame-flame interactions give rise to local extrema in progress variable dissipation rate at non-zero/-unity progress variable. This work explores the influence of flame-flame interactions on the local thermochemical state using Direct Numerical Simulation of turbulent premixed planar hydrogen/air flames. The conditional statistics of this database are compared to predictions from the manifold model using local progress variable dissipation rates extracted from the databases. The work concludes by discussing what additional physics, if any, may be needed in the manifold model to capture flame-flame interactions.