Stretch Rate and Displacement Speed Correlations for Increasingly-Turbulent Premixed Flames

Probability density functions of the components of stretch rate are investigated using a previously-published Direct Numerical Simulation dataset spanning a range of turbulence intensities in the Thin Reaction Zones (TRZ) regime. The dataset was generated by varying the turbulence intensity across five different simulations while maintaining fixed the remaining physico-chemical input parameters such as integral length scale and laminar flame thickness and speed. Across the entire dataset, the joint probability density function of stretch rate and displacement speed displays a distinctive shape with two branches consistent with previous studies at low turbulence intensities. This joint probability density function is analysed further by extracting individual contributions of stretch rate components to determine their relative importance across the branches. The curvature dependence of displacement speed appears to play an important role in shaping these branches. Implications of this result with regard to evaluation of the components of stretch rate in the TRZ regime are discussed.