Intermittency in Premixed Turbulent Reacting Flows

Characterizing the intermittency of velocity gradient and scalar gradient fields in turbulent reacting flows is important for developing a better understanding of the interactions between turbulence and flames. Here we examine intermittency in premixed reacting flows using numerical simulations of stoichiometric hydrogen-air combustion at a range of turbulence intensities. Simulations of homogeneous isotropic turbulence with a nonreacting passive scalar are also carried out in order to allow comparisons with the reacting flow results. We examine intermittency by calculating probability density functions and moments of the local enstrophy, energy dissipation rate, and scalar dissipation rate. Conditional analyses based on local, instantaneous values of the reactant mass fraction are used to study variations in the statistics through the flame. We observe variations in the intermittency depending on the intensity of the turbulence, the location in the flame, and the quantity under consideration. We discuss the implications of these results for the flame structure, and also provide an explanation for the observed results by considering the two-way interactions between turbulence and premixed flames.