Small-scale intermittency of turbulent premixed flames

Premixed turbulent flames play a central role in combustion and power generation devices, and are an archetype of randomly advected, self-propagating surfaces. The interaction of premixed flames with turbulence are, thus, of practical and fundamental importance. While much is known about their large-scale behaviour, the dynamics of small-scale fluctuations are not well understood. From temporally resolved experimental data of methane-air V-flame, we reveal self-similar scaling and small-scale intermittency in the fluctuations of the premixed flame. We show that the frequency spectra follows a power-law behaviour with a slope of -2 in the inertial sub-range, which is rationalized in terms of the flame surface passively responding to inertial range eddies. Upon quantifying the higher-order statistics, we find that the structure-functions scale anomalously, with high frequency fluctuations depicting increasingly non-Gaussian behaviour—a signature of small-scale intermittency. Our study have important implications for modeling turbulent flame speeds and heat release rate in premixed flames.