Backscatter of scalar variance in turbulent premixed flames

To explore the direction of inter-scale transfer scalar variance between subgrid scale (SGS) and resolved fields, direct numerical simulation data obtained earlier from two complex-chemistry lean hydrogen–air flames are analysed by applying Helmholtz–Hodge decomposition (HHD) to simulated velocity fields. Computed results show backscatter (combustion progress variable $c$ ) variance, i.e. its SGS scales, even in a highly turbulent flame characterized unity-order Damköhler number ratio Kolmogorov length thermal laminar thickness as low 0.05. Analysis fluxes associated with solenoidal potential fields yielded HHD shows that documented stems primarily perturbations generated due dilatation instantaneous local flames, being substantially promoted close alignment spatial gradient mean potential-velocity contribution flux. The is fact combustion-induced expansion increases $\boldsymbol {\nabla } c$ . These call for development models capable predicting large eddy simulations.