DNS analysis of flame propagation for systematic variations in turbulence scales and intensity

Direct Numerical Simulation (DNS) of premixed hydrocarbon flames is performed using the DNS code Senga2 to investigate the role of varying integral length scale $l_{\mathrm{0}}$ as well as the turbulence intensity u` in the thin reaction zone regime. Different cases are studied by either systematically varying $l_{\mathrm{0\thinspace }}$at constant u` or by systematically varying u` at constant$ l_{\mathrm{0}}$. Several aspects of these flames are compared. The turbulent flame speed $s_{T}$ is found to decrease as $l_{\mathrm{0\thinspace }}$decreases or when u` increases. The ratio of $s_{T} / s_{L}$ is generally accounted for by the area change $A_{T} / A_{L}$ but a significant deviation is observed between these values at high u` cases. The size of the smallest scales of turbulence also decreases with $l_{\mathrm{0\thinspace }}$and the interaction of these small scales with the flame produces an increase in the mean curvature of the flame which eventually reaches a saturation point. There is also an increase in the number of flame-flame interactions with decreasing $l_{\mathrm{0}}$. Individual flame-flame interaction topologies are identified and analysed. All these findings serve to further our understanding of turbulent combustion and the role that the turbulence length scales play in flame propagation.