Abstract
The statistical behaviour of turbulent scalar flux (TSF) and modelling of its transport have been analysed for major species (H-2, O-2 and H2O) in the context of Reynolds-Averaged Navier Stokes simulations using a detailed chemistry Direct Numerical Simulation database of freely-propagating H-2 - air flames spanning the corrugated flamelets (CF), thin reaction zones (TRZ) and broken reaction zones (BRZ) regimes of premixed turbulent combustion. The TSF in the CF and TRZ regimes exhibits counter-gradient transport, whilst gradient transport was found in the BRZ regime. The TSF transport equation terms' exhibited similar behaviour in the CF and TRZ regimes, but significantly differed in the BRZ regime. Similar behaviour for different terms in the TSF equation has been observed for the major reactants, while the major product shows an opposite sign. Based on a priori assessment of existing models it has been found that they perform reasonably well in the CF and TRZ regimes, but are inadequate for the BRZ regime.