A numerical investigation of stretch effects in counterflow, premixed laminar flames

We use direct numerical simulation of propane/air flames with full chemistr y in the geometry of stagnation flow to investigate the effect of different definitions of local flame stretch in the presence of spatially varying ve locity gradients. Specifically, we compare simulations with potential- and plug-flow inlet conditions, and show that the widely used definition of ups tream stretch leads to unphysical results for flames having the 'same' stre tch. We then show that a reasonable re-definition of local stretch allows u s to produce the 'same' flame in the presence of the 'same' stretch.