The effect of differential molecular diffusion (DMD) in turbulent non -premixed flames is studied by examining two previously reported DNS of temporally evolving planar jet flames, one with CO/H-2 as the fuel and the other with C2H4 as the fuel. The effect of DMD in the CO/H-2 DNS flames in which H-2 is part of fuel is found to behave similar to laminar flamelet, while in the C2H4 DNS flames in which H-2 is not present in the fuel it is similar to laminar flamelet in early stages but becomes different from laminar flamelet later. The scaling of the effect of DMD with respect to the Reynolds number Re is investigated in the CO/H-2 DNS flames, and an evident power law scaling (similar to Re-a with a a positive constant) is observed. The scaling of the effect of pm)) with respect to the Damkohler number Da is explored in both laminar counter-flow jet C2H4 diffusion flames and the C2H4 DNS flames. A power law scaling (similar to Da(a) with a a positive constant) is clearly demonstrated for C2H4 nonpremixed flames. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.