Multicomponent transport impact on turbulent premixed H2/O2 flames

We investigate the impact of multicomponent transport on premixed turbulent H-2/O-2 flames. The present direct numerical simulation (DNS) database contains 15 flame configurations where freely propagating planar flames interact with counter-rotating vortices and synthetic turbulence fields. The DNS solver considers the conservation equations for species, momentum and energy with complex chemistry and detailed transport in two space dimensions and in the low Mach number regime. Accurate transport algorithms accounting for both multicomponent molecular and thermal diffusion are implemented in this solver at low computational costs. Multicomponent transport may lead locally in space or time to substantial modifications of turbulent flame properties. These modifications can be much larger than those observed for laminar flames. They are particularly noticeable on the propagation velocity and thus on the stretch in regions where the flame front experiences strong curvature effects. For most flames studied here, multicomponent transport has only a moderate impact on global flame properties because of the smoothing induced by turbulent fluctuations. Thus, the present DNS results, which for the first time incorporate detailed transport models, provide a form of a posteriori validation for previous DNS based on simplified transport models. However, for highly curved flames or when quenching phenomena arise, multicomponent transport plays a sufficiently relevant role to be included in accurate DNS.